sports medicine Volume 39 Issue 11 November 2009

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Sports Med 2009; 39 (11): 889-901 0112-1642/09/0011-0889/$49.95/0

LEADING ARTICLE

ª 2009 Adis Data Information BV. All rights reserved.

Design of the iPlay Study Systematic Development of a Physical Activity Injury Prevention Programme for Primary School Children Dorine C.M. Collard,1 Mai J.M. Chinapaw,1,2 Willem van Mechelen1,2 and Evert A.L.M. Verhagen1 1 EMGO Institute for Health and Care Research and Department of Public and Occupational Health, VU University Medical Center, Amsterdam, the Netherlands 2 Research Centre Body@Work TNO VUmc, Amsterdam, the Netherlands

Abstract

Health benefits of physical activity in children are well known. However, a drawback is the risk of physical activity-related injuries. Children are at particular risk for these injuries, because of a high level of exposure. Because of the high prevalence of physical activity injuries and the negative short- and long-term consequences, prevention of these injuries in children is important. This article describes how we systematically developed a school-based physical activity injury prevention programme using the intervention mapping (IM) protocol. IM describes a process for developing theory- and evidence-based health promotion programmes. The development can be described in six steps: (i) perform a needs assessment; (ii) identify programme and performance objectives; (iii) select methods and strategies; (iv) develop programme; (v) adopt and implement; and (vi) evaluate. First, the results of the needs assessment showed the injury problem in children and the different risk factors for physical activity injuries. Based on the results of the needs assessment the main focus of the injury prevention programme was described. Second, the overall programme objective of the injury prevention programme was defined as reducing the incidence of lower extremity physical activity injuries. Third, theoretical methods and practical strategies were selected to accomplish a decrease in injury incidence. The theoretical methods used were active learning, providing cues and scenariobased risk information, and active processing of information. The practical strategy of the injury prevention programme was an 8-month course about injury prevention to be used in physical education classes in primary schools. Fourth, programme materials that were used in the injury prevention programme were developed, including newsletters for children and parents, posters, exercises to improve motor fitness, and an information website. Fifth, an implementation plan was designed in order to ensure that the prevention programme would be implemented, adopted and sustained over time. Finally, an evaluation plan was designed. The injury prevention programme is being evaluated in a cluster randomized controlled trial with more than 2200 children from 40 primary schools throughout the Netherlands.

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The IM process is a useful process for developing an injury prevention programme. Based on the steps of the IM we developed an 8-month injury prevention programme to be used in physical education classes of primary schools.

Regular physical activity (PA) has many health benefits, for example it lowers the risk of obesity, coronary heart disease and osteoporosis.[1-3] A drawback of increased PA levels is the risk of PA-related injuries. Sports are the leading cause of injury and hospital emergency room visits in adolescents.[4-5] The high prevalence of PA injuries in children and the negative short- and long-term consequences confirm its importance as a health problem. Although most PA injuries are not life threatening, the occurrence of PA injury can result in pain, disability, school absence, absence from PAs and sometimes in dysfunction in the short and long term. Therefore, prevention of PA-related injuries is essential. Emery[6] showed in a review that injury prevention strategies in children can reduce the risk of PA injuries. However, the literature has some limitations and is based primarily on observational studies for specific injuries and specific sports.[7] Few studies on school-based PA injury prevention strategies have been published. Of these, only one study was a randomized controlled trial.[8] Measures to prevent PA injuries should generally be based on knowledge about the incidence and severity of the PA injury problem, aetiological risk factors, and mechanisms contributing to the risk of sustaining such injuries.[9] Because a proper school-based PA injury prevention programme in children does not exist and evidence on effectiveness is lacking, development and evaluation of such a programme is necessary. An injury prevention programme can be developed using the intervention mapping (IM) protocol.[10,11] IM describes a process for developing theory- and evidence-based health promotion programmes, and involves a systematic process that prescribes a series of six steps: (i) performing a needs assessment; (ii) defining suitable programme objectives; (iii) selecting theory-based intervention methods and practical strategies; (iv) producing ª 2009 Adis Data Information BV. All rights reserved.

programme components and materials; (v) designing an implementation plan; and (vi) designing an evaluation plan (see figure 1). Collaboration between the developers, the users of the intervention and the target population is a basic assumption in the IM process.[12] This article describes in detail the development of a PA injury prevention programme for children by using the steps of the IM process. Step 6 of the process descibes in detail how to evaluate the effectiveness of such a programme. 1. Step 1: Perform a Needs Assessment Prior to the development of a PA injury prevention programme for children, the injury problem and the risk factors for PA injuries in children should be assessed. In order to gain insight into the needs of the target population, a focus group interview with 23 physical education (PE) teachers from 12 secondary schools was carried out. 1.1 The Injury Problem

Injuries cause children unnecessary suffering and pain in the short term.[1,8,13] Individuals who have experienced macro trauma or PA injuries to joints may be at risk of accelerated development of (secondary) osteoarthritis in later life.[14] Moreover, it is suggested that PA injuries sustained Step 1: Needs assessment Step 2: Define suitable programme objectives Step 3: Select theory-based intervention methods and practical strategies Step 4: Produce programme components and materials Step 5: Design an implementation plan Step 6: Design an evaluation plan Fig. 1. Steps of the intervention mapping process.

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Developing a Physical Activity Injury Prevention Programme

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Table I. Risk factors for physical activity injuries in children[5] Extrinsic risk factors non-modifiable

potentially modifiable

Intrinsic risk factors non-modifiable potentially modifiable

Sport played (contact/no contact)

Rules

Previous injury

(Aerobic) fitness level

Level of play (recreational/elite)

Playing time

Age

Pre-participation in sport-specific training

Position played

Playing surface (type/condition)

Sex

Flexibility

Weather

Equipment (protective/footwear)

Time of season/time of day

Strength Joint stability Biomechanics Balance/proprioception Psychological/social factors

at a young age have a negative influence on participation in PAs and sports.[15,16] Data from the period 2000–2004 revealed that in the Netherlands 1.5 million acute PA injuries are reported each year and 51% of these injuries are medically treated. The PA injury incidence in children aged 0–17 years is 1.3 (95% CI 1.2, 1.4).[17] The absolute number of PA injuries in the Netherlands increases for both sexes until the age of 12 years. Above this age, injuries in boys increase considerably until the age of 16 years. The highest number of PA injuries in girls is registered at 14 years of age. The most frequently injured body parts are the lower extremities. The ankle is the most affected part of the body (20%), followed by the knee (18%).[17] Although sport participation in children has increased (children aged 6–11 years: 88% in 1991 to 93% in 2003; children aged 12–19 years: 84% in 1991 to 93% in 2003), membership of sports clubs has decreased (children aged 6–11 years: 76% in 1991 to 74% in 2003; children aged 12–19 years: 77% in 1991 to 71% in 2003).[18] There are a large number of children who participate in organized team sports, but a growing number of children are attracted to non-organized sports activities and individual sports. There seems to be a trend for individualization, and children nowadays are attracted to sports other than traditional sports in a sport club.[19] The literature shows that most PA injuries occur during non-organized sports activities and leisure time.[20-22] Data from a nationwide survey in the Netherlands showed that school absence occurs ª 2009 Adis Data Information BV. All rights reserved.

in 7% of the children who sustained a sports injury, and the mean duration of school missed by these children was 8 days. This means that 0.02% of the total population who visit school and participate in sports are absent from school one or more days. With a mean duration of 8 days, the total school absence due to sports injuries can be calculated at 794 000 days a year. In addition, 22% of the people who sustained a PA injury were also absent from PAs.[17] The economic consequences of PA injuries in children are not known, but direct medical costs, for example medical treatments as a result of all PA injuries, were estimated at h170 and indirect medical costs, for example work or school absence, were estimated at h420 million (year of costing 2003).[23] Risk factors for PA injuries are factors that increase the potential risk for injury and include extrinsic risk factors (i.e. weather, field conditions) and intrinsic risk factors (i.e. age, conditioning). Identification of risk factors can be used as a leading guide for preventive measures. However, it is clear that injuries are caused mostly by a combination of factors. Table I shows the most important risk factors for PA injuries in children.[5] Based on these data, the aim our injury prevention programme should be to prevent lower extremity PA injuries in school children. A prevention programme to prevent PA injuries embedded in PE classes in schools will reach all the children who are physically active – not only children in sport clubs. PA injuries are defined as injuries occurring during organized sports activities, leisure time activities and PE class. Sports Med 2009; 39 (11)

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1.2 Focus Group Interviews

In order to gain insight into the needs of the target population and in order to be able to design a feasible intervention programme, focus group interviews were held. Five individual interviews and two focus group interviews were performed with 23 PE teachers from 12 secondary schools. In the Netherlands, children go to primary school until the age of 12 years, followed by attendance at secondary school. The interviewed secondary school PE teachers generally agreed there is a great diversity in physical fitness and motor performance in children in the first grade of secondary schools. Their common opinion was that these interindividual differences are an important contributing factor to PA injuries in children. Asking the interviewed PE teachers about the causes of the noted diversity in physical fitness and motor control, and particularly about possible solutions, they argued that an intervention programme should focus on primary school children. In primary schools, children receive regular PE classes. Unfortunately, these regular PE classes are not always supervised by certified PE teachers (due to economic reasons, the child’s regular teacher often provides the PE classes). However, the regular teachers usually do not incorporate injury prevention aspects in their PE classes; as general injury prevention lessons are not given in primary schools, it is likely that a preventive intervention in this setting can lead to maximum improvement. In addition, the PE teachers in secondary schools said they were hesitant and not motivated to incorporate our preventive intervention in their PE classes, because they already incorporated their own injury prevention in their PE classes. Because the PE teachers in secondary schools argued that the intervention programme should focus on primary schools since injury prevention lessons are already given in secondary schools, a shift from secondary school children to primary school children was made. From the focus group interviews with the PE teachers we also learned that, in general, the PE teachers were rarely confronted with injuries, and they were unaware of a sports injury problem ª 2009 Adis Data Information BV. All rights reserved.

among their pupils. From the interviews it became clear that raising injury knowledge in children, teachers and parents should be an important objective for our intervention programme. 2. Step 2: Define Suitable Programme Objectives This step provides the foundation for the programme by specifying who and what will change as a result of the intervention. The overall objective of our intervention programme was to reduce the incidence of lower extremity PA injuries. In order to achieve this overall objective, several risk-reduction behavioural and interpersonal environment ‘sub-objectives’ were defined that focus on children, parents and PE teachers. The underlying assumption of the risk-reduction behavioural sub-objectives is that if an intervention reduces the prevalence of risk factors, it will reduce the prevalence of PA injuries. Furthermore, the presence or absence of support from important others (e.g. parents, PE teachers) within the individual’s immediate interpersonal environment may have an influence on the performance of the injury-preventing behaviour.[24] The subobjectives used in our preventive measure are: (i) children take fewer injury-related risks; (ii) parents create a safe PA environment for their children outside PE classes; (iii) and teachers include injury prevention into their usual teaching routine. Performance objectives were defined on the basis of the programme objectives and describe what the participants in this programme need to do to perform the desired injury-preventing behaviour. The performance objectives for each programme objective are presented in table II. 3. Step 3: Select Theory-Based Intervention Methods and Practical Strategies The third step of the IM process is the selection of theory-based intervention methods and practical strategies to effect changes in the health behaviour of individuals, and to change organizational and societal factors to alter the environment. Sports Med 2009; 39 (11)


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Table II. Performance objectives for the four different programme objectives Performance objective

Programme objective 1: children will take fewer injuryrelated risks

Programme objective 2: parents will create a safe physical activity environment outside PE classes

Programme objective 3: PE teachers will include injury prevention into their usual teaching routine

1

Children learn the consequences of an injury

Parents learn the consequences of an injury

PE teachers learn the consequences of an injury

2

Children learn which risk factors cause injuries

Parents learn which risk factors cause injuries

PE teachers learn which risk factors cause injuries

3

Children gain insight into their own injury risk behaviour

Parents gain insight into the injury risks during the child’s leisure time physical activities

PE teachers gain insight into the pupils’ risk behaviour

4

Children form strategies to reduce their injury risk

Parents form strategies to reduce the injury risk during the child’s leisure time physical activities

PE teachers form strategies to reduce the pupils’ risk behaviour

5

Parents gain insight into the child’s risk behaviour

6

Parents form strategies to reduce the child’s risk behaviour

PE = physical education.

A ‘method’ can be described as a theoretically derived technique used to influence (determinants of) injury-preventing behaviour, and a ‘strategy’ as a practical way of organizing and delivering the intervention method.[12,25] 3.1 Theory-Based Intervention Methods

Preventive measures should target one or more of the risk factors mentioned earlier (table I). A potentially modifiable risk factor for PA injuries in children is wearing appropriate protective equipment and footwear during PAs. To decrease this risk factor, injury-preventing behaviour should be addressed. Injury-preventing behaviour is an indirect causal factor for PA injuries.[26] Therefore, improving this behaviour could be a method to decrease PA injury incidence and PA injury severity. To change injury-preventing behaviour, knowledge of determinants of behaviour is necessary.[27] We applied the attitude, social influence and self-efficacy (ASE) model for behaviour change. The ASE model is based on the theory of planned behaviour[28] and the social learning theory.[29] This model[30,31] postulates that intention, the most proximal determinant of behaviour, is determined by three conceptually independent constructs: attitude, social influence and self-efficacy. To change injury-preventing behaviour and finally decrease injury incidence, our programme ª 2009 Adis Data Information BV. All rights reserved.

tries to improve attitude, social influence, selfefficacy and intention towards wearing appropriate protective equipment and footwear during organized PAs, leisure time activities and PE classes (see figure 2). In addition, a second potentially modifiable risk factor for PA injuries in children is dimensions of motor fitness (e.g. flexibility, strength and balance/proprioception). Motor fitness and sport-specific skills have an impact on sports injuries.[32] There is some evidence that improving certain dimensions of motor fitness can decrease PA injuries. However, this evidence is found in sport-specific studies[33-38] (see figure 2). Theoretical methods are general techniques for influencing changes in determinants of behaviour. In our programme the following methods will be used: active learning, providing cues and scenario-based risk information, and active processing of information.[24] The related theories for the adopted methods are the persuasion communication matrix, elaboration likelihood, social cognitive theory, theories of information processing, and a precaution adoption process model.[24] 3.2 Practical Strategies

The next step is to translate the methods into practical strategies that can be used in a preventive measure. Knowledge is a basis for many different determinants of behaviour, but giving Sports Med 2009; 39 (11)

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Attitude The degree to which performance of injurypreventing behaviour is positively or negatively valued Social influence Consists of three components: - Subjective norms - Social support - Pressure and modelling

Intention

Injury-preventing behaviour

Decrease PA injury incidence rates Decrease severity of PA injuries

Self-efficacy The subjective probability that a person is capable of executing injury-preventing behaviour Motor fitness Dimensions of motor fitness are strength, flexibility, speed, power and balance/coordination Fig. 2. A conceptual model of injury prevention. PA = physical activity.

children information will not lead directly to behavioural change. However, behavioural determinants like attitude are based partly on knowledge.[39] The practical strategy that is used to deliver information in order to increase attitude, social influence, self-efficacy and motor fitness is an 8-month course about injury prevention. The communication channels are a course manual for teachers, newsletters for children and parents, posters for children, an exercise programme during PE lessons for children, and an interactive website. The newsletters can be made especially for children or parents, and the willingness to receive a newsletter is usually good.[24] In addition, posters can be effective in calling attention to a campaign and they provide continuous exposure to the children.[24] Table III gives an overview of the determinants, methods, theories and strategies to reach the programme objectives. 3.3 Interpersonal Environment

Changing determinants of behaviour is almost always embedded in one or more environmental levels. A child participating in PAs is in an environment with parents and PE teachers, thereª 2009 Adis Data Information BV. All rights reserved.

fore parents and PE teachers should also be involved in the intervention programme.[24] Parents are very important in creating a safe PA environment outside PE classes. They should encourage their children to play safe,[40] and they are important as role models for their children. The influence of parental rules and pressure has been found to have a strong effect on the use of protective equipment.[41-43] PE teachers are very important in creating a safe PA environment during PE classes. In order to prevent injuries in PE classes it is important that teachers include injury prevention into their usual teaching routine. If PE teachers include injury prevention into their teaching routines, they will teach children how to prevent injuries during PAs, not only during PE classes, but also outside school. 4. Step 4: Produce Programme Components and Materials The task in this step of the IM process is to translate methods and practical strategies into programme components and materials. Our injury prevention programme as a whole is not Sports Med 2009; 39 (11)


specified for any specific type of sport. It addresses the most common injuries and preventive measures in general and includes the programme components and materials outlined below. 4.1 Newsletters

Monthly newsletters are produced for both children and parents. The aim of the newsletters is to increase knowledge and awareness about injury prevention. The monthly newsletters consist of information about injury prevention, selfevaluation tests and puzzles on a specific topic. By providing a monthly newsletter, new information will be given each month in a motivational way. It is believed that this will remind all involved each month of the task of preventing PA injuries.

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speed, balance/coordination and flexibility). The exercises are developed on the basis of exercises from ‘active childhood-healthy life’,[44] exercises from ‘Basisdocument Bewegingsonderwijs’,[45] and exercises from a programme to prevent lower limb injuries in youth sports.[37] Table IV gives examples of the exercises that are done during the PE classes. 4.4 Website

The website (www.iplaystudy.nl) contains general information about injury prevention for children, parents and PE teachers, who can view the newsletters online, and children can check their solutions to the newsletter puzzles. Additionally, various instruction videos and photos are displayed to illustrate for PE teachers how to teach the exercises.

4.2 Posters

Eight different posters (A1 size, i.e. 594 · 840 mm) show the highlights of the content of the newsletters. The posters contain important and clear messages about injury prevention and are very colourful and have humorous cartoon images in order to make the posters attractive to children. They are displayed in the classroom, so that the children are able to see the posters continuously. 4.3 Exercises to Improve Motor Fitness

A short training circuit is performed at the beginning and the end of each PE class, twice a week. This circuit consists of exercises aimed at the improvement of motor fitness (i.e. strength,

4.5 Pretesting and Revising

Pilot testing of programme strategies and materials with intended implementers and recipients is an important part of step 4. 4.5.1 Pretesting the 8-Month Course

Teachers and children of six primary schools were informed about the programme in full detail. Teachers were asked for their comments on the topics and timing of the different modules of the 8-month course via a focus group interview. With the exception of a few minor comments, all interviewed primary school teachers were positive about the programme and believed the programme to be feasible and effective. Children

Table III. Theoretical methods and practical strategies to reach programme objective Determinants

Methods

Theory

Strategies

Attitude

Active learning

Persuasion communication matrix

Newsletter delivered to children and parents to improve knowledge

Social influence

Cues

Elaboration likelihood

Posters exposed to children in the classroom to improve knowledge

Self-efficacy

Scenario-based risk information

Social cognitive theory

Course manual for teachers

Motor fitness

Active processing of information

Theories of information processing

Short circuit training to improve motor fitness during physical education classes

Precaution adoption process model

Website accessible for children, parents and teachers


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Table IV. Examples of the iPlay-programme of exercises used to prevent injuries Strength

Coordination

Speed

Forward jumps

Passing the ball (one leg stance)

Shuttle run

Flexibility of hamstring

Squats to 80 of knee flexion

Skate jumps

Race course

Flexibility of calf muscle

Hand wrestling in push-up stand

Pushing each other off balance (one leg stance)

Spurts from different start positions

Flexibility of biceps femoris

responded in a comparable way and were very enthusiastic about the monthly newsletters and posters. Although the programme also targets parents, for practical reasons they were not asked for their comments about the 8-month course. However, the positive response of teachers and children led us to believe that the programme will be widely accepted in its current form. 4.5.2 Pretesting Exercise Programme

The exercise programme to improve motor fitness was pretested in two different primary schools, involving three PE teachers. Teachers were asked specifically for their comments on the feasibility of the exercises, the level of intensity, the degree of difficulty of the exercises and the clarity of the manual. Some exercises were perceived as too difficult or taking too much time. Additionally, the teachers advised delivery of the exercises in a more competitive and playful way. Exercises were adapted as suggested by the PE teachers. The teacher’s manual was considered to be very clear. 5. Step 5: Design an Implementation Plan This step focuses on the design of an implementation plan, in order to ensure that an injury prevention programme will be implemented, adopted and sustained over time. The intervention programme is a ‘ready to use’ preventive measure so it can be implemented directly in PE lessons, if proven effective. The Royal Association of Teachers of Physical Education (KVLO) and the Academy for PE Teachers’ Education will then play an important role in the implementation. The KVLO controls the standards and continuity of physical education in the Netherlands, and has a wide array of implementation channels. Thereby, the KVLO will ª 2009 Adis Data Information BV. All rights reserved.

Flexibility

be an important channel through which the preventive programme can be implemented not only by today’s PE teachers, but also by the PE teachers of the future. Another channel that plays an important role in successful implementation is the academic school where PE teachers are educated. The KVLO and the Academy for PE Teachers’ Education have been involved in the study from the very beginning and have participated in the IM process. By using IM, the programme was tailored to the wishes of the end users. In doing so, the practical and logistical issues of implementation have been minimized. 6. Step 6: Design an Evaluation Plan Through effect and process evaluation, IM planners can determine whether decisions were correct at each mapping step. To evaluate the effect of the intervention, the decrease in injury incidence will be analysed in a cluster randomized controlled trial. The primary research questions addressed are: ‘‘What is the effect of the injury prevention programme on lower extremity PA injury incidence and severity?’’ and ‘‘What is the cost effectiveness of this programme?’’ The secondary research question is: ‘‘What is the effect of the injury prevention programme on the improvement of knowledge, (determinants of) injury-preventing behaviour and motor fitness?’’ 6.1 Sample Size

A difference in the incidence of acute lower extremity injuries of 7% between the intervention and control group after 8 months is considered clinically relevant. To detect a difference of 7% in the incidence of lower extremity PA injures with a power of 90% and an a of 5%, 500 children per group (intervention/control) are needed in an Sports Med 2009; 39 (11)


evaluation study. However, in order to perform multi-level analyses taking into account a cluster randomization design (schools as randomization level) – with an intra-cluster correlation coefficient of 10% and a dropout rate of 20% – a total of 2280 children from 40 schools are required at baseline. 6.2 Recruitment 6.2.1 Recruitment of Primary Schools

The evaluation will be carried out in Dutch primary schools. From the 7000 primary schools throughout the Netherlands, 520 primary schools are randomly selected from a database and invited by means of an information flyer. Inclusion criteria for the primary schools are: (i) being a regular primary school; (ii) giving PE lessons twice a week; and (iii) being willing to appoint a contact person for the duration of the study. A flowchart of the recruitment of primary schools is given in figure 3. 6.2.2 Recruitment of Children and their Parents

The children and parents from the participating schools receive an information letter about the study design. All children are eligible for inclusion in the study. The parents receive a passive informed consent request: this consent procedure assumes that the parents consent, unless the

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researcher is contacted by means of a telephone call or by sending an email. 6.3 Randomization

Schools serve as randomization units to avoid spillover of the intervention within schools. A stratified randomization is performed based on geographic location (urban/suburban) and professional status of the PE teacher (certified/ uncertified), resulting in four strata. From each stratum, schools are randomly allocated to the intervention or control group by a computerized random number generator. Before the school year starts, the primary schools are informed about the group (intervention/control) they are assigned to. 6.4 Primary Outcome Measures 6.4.1 Injury Definition and Registration

Throughout the school year, PA injuries are recorded continuously by PE teachers. They are instructed to question children explicitly every week about whether they have been injured as a result of PAs (including non-organized events) in the past week. The injury definition, as described by van Mechelen et al.,[9] is used where a PA injury is any injury as a result of participation in PE class, sport activities or leisure time PAs

520 primary schools 370 primary schools did not respond at all

105 primary schools not willing to participate

45 primary schools willing to participate

40 primary schools participate in the iPlay study (n = 2210)

Reasons: - No time (n = 58) - Missing value (n = 15) - Not relevant (n = 10) - Already participating in other project (n = 8) - No interest (n = 8) - Change in teacher (n = 5)

Five primary schools were excluded: - Only once-a-week PE class (n = 3) - Change in teacher at the beginning of the school year (n = 1) - Already participates in the study with another primary school (n = 1) Control group = 20 schools (n = 1093) Randomization Intervention group = 20 schools (n = 1117)

Fig. 3. Flowchart of recruitment in primary schools. PE = physical education.


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with one or more of the following consequences: the child (i) has to stop the physical activity and/or (ii) cannot (fully) participate in the next planned PA (applies also to planned leisure time PAs) and/or (iii) cannot go to school the next day and/or (iv) needs medical attention ranging from onsite care (e.g. first-aid personnel) to personal care (e.g. physiotherapist or sports physician). In case of an injury, the child is asked to complete an injury registration form. The injury registration form collects information on injury type, injury location, direct cause of the injury and activity performed at the time of injury. Injury incidence refers to the number of new PA injuries during a particular period of time (e.g. 1 year). One method to express incidence rates is to calculate the incidence of PA injuries in relation to exposure (in days, hours or sport event). To determine time at risk for PA injuries, all children complete a questionnaire in the classroom twice a year. This questionnaire collects information on exposure time (sports and leisure-time PA participation). 6.4.2 Cost Effectiveness

In order to evaluate the cost effectiveness of the preventive measure, all parents from children who sustain a PA injury receive a cost diary. The cost diary is a log in which parents register all (para-) medical treatment (including use of medication), absence from school and sport activities, and other discomfort from the moment of injury onwards, until full recovery. From these cost diaries, direct and indirect costs resulting from the sustained injury can be calculated for use in the economic evaluation. 6.5 Secondary Outcome Measures

Knowledge, injury-preventing behaviour, behavioural determinants and motor fitness are measured at baseline (start of the school year) and follow-up (end of the school year). 6.5.1 Questionnaires

Children are requested to complete a questionnaire in the classroom. The children take home the questionnaire to their parents, who are asked to complete their questionnaire and return ª 2009 Adis Data Information BV. All rights reserved.

it to the research team in a pre-stamped reply envelope. Knowledge about injury prevention is measured with one question on self-reported improvement in knowledge of how to prevent PA injuries, as well as a knowledge test including nine multiple-choice questions about injury prevention in general. Behavioural determinants are assessed with the following constructs: attitude, social influence, self-efficacy and intention. The injurypreventing behaviour is defined as wearing appropriate protective equipment and footwear during organized PAs, leisure time and PE class. Attitude towards the injury-preventing behaviours is assessed with three questions. Social influence is assessed with questions regarding social norm, modelling of friends, and modelling of parents. Self-efficacy is assessed with two questions relating to the child’s perception of their ability to perform injury-preventing behaviour. Intention and behaviour towards wearing protective equipment and appropriate shoes during organized PAs, leisure time and PE class are assessed with one question. All answers on the questions are given on a five-point Likert scale varying from always (1) to never (5) or totally agree (1) to totally do not agree (5). All questions are positively formulated. We pretested the questionnaires on comprehensibility, (lack of) clarity and practical applicability in 54 children and their parents. Based on the results of the pretest, we changed some questions to increase comprehensibility, deleted excessive text messages and shortened the questionnaire to decrease completion time. 6.5.2 MOPER Fitness Test

Motor fitness is assessed with the MOtor PERformance (MOPER) fitness test. Supervised by a research assistant, groups of three to four children perform seven test items of the MOPER fitness test (bent arm hang test, 10 · 5 m run test, plate tapping test, leg lift test, sit and reach test, arm pull test and standing high jump test), and they are asked to perform all test elements as well as possible. For practical reasons, we decided to exclude the 6-minute endurance run. For an Sports Med 2009; 39 (11)


extensive description of the MOPER fitness test items, see Leyten et al.[46] In addition, children perform the flamingo balance test, which has been described in the EUROFIT test.[47] To be able to complete all tests during one PE class we shortened the flamingo balance test to 30 seconds instead of 1 minute as the original flamingo balance test protocol indicates. All test items are performed barefoot to rule out the effect of footwear on the test results. Body height and weight are also measured. Body height is measured in metres to the nearest centimetre with a portable stadiometer (Seca 214, Leicester Height Measure; Seca GmbH & Co, Hamburg, Germany). Asking the subject to stand straight, with the heels together and looking straight ahead, standardizes positioning of the body. Body weight is measured to the nearest 0.1 kg with a digital scale (Seca 770; Seca GmbH & Co, Hamburg, Germany). During the body height and weight measurements, children wear only underwear. 6.6 Statistical Analysis

The effects of the intervention will be assessed using multilevel regression analysis. This statistical technique takes into account the dependency of observations of different children from the same class and school. Analyses will be adjusted for baseline values and, if necessary, for other confounders. The economic evaluation will be assessed using mean direct (i.e. medical costs), indirect (i.e. costs for absence from school/work) and total costs from the cost diaries. Because costs are generally not normally distributed, 95% confidence intervals for the differences in mean costs will be obtained by bias-corrected and accelerated bootstrapping. Differences in costs and differences in injury incidence will be included in a cost-effectiveness ratio, which estimates the additional costs to prevent one PA injury. 6.7 Process Evaluation

A process evaluation is included to monitor programme implementation, which will gain insight into the relationship between specific proª 2009 Adis Data Information BV. All rights reserved.

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gramme elements and programme outcomes.[48] The injury prevention programme will be evaluated with the use of the RE-AIM (reach, efficacy/ effectiveness, adoption, implementation and maintenance) framework.[49] All PE teachers, children and parents assigned to the intervention group are asked to complete the process evaluation questionnaire.

7. Discussion and Conclusions Regular PA has many health benefits, but also increases the risk of PA injuries. This paper describes how to develop and evaluate a preventive measure using the IM protocol. To our knowledge, this is the first time this has been done in the injury prevention field. Although this strategy has never been used before in this field, the underlying systematic ‘evidence-based’ process and the contribution of the field of practice make the IM method likely superior to any other method for developing an injury prevention programme. The IM protocol provides a valuable checklist for the development of an intervention programme. However, it is a rather time-consuming process. The research on determinants, definition of suitable performance objectives, moving back and forth between the IM steps, and the pretesting of materials required much time. This makes it sometimes difficult to apply the IM process according to the full instructions. The results of the evaluation study will be published elsewhere. Preliminary analysis clearly indicates that the iPlay study resulted in a significant decrease in injury incidence in the intervention group. Moreover, the results of the evaluation study will help to gain more insight into the effects of school-based injury prevention programmes. Acknowledgements The iPlay study is supported by a grant from the Netherlands organization for health research and development (ZONMW), grant number 62200033. The authors have no conflicts of interest that are directly relevant to the content of this review.

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Authors’ contribution: EV was involved in developing the concept and the design of the study. DC, MC and EV were involved in further developing the idea and the protocol for carrying out the study. DC was responsible for the data collection and she drafted the manuscript. All authors contributed to the final manuscript by reading and correcting draft versions.

References 1. Adirim TA, Cheng TL. Overview of injuries in the young athlete. Sports Med 2003; 33 (1): 75-81 2. Ekblom B, Astrand PO. Role of physical activity on health in children and adolescents. Act Paediatr 2000 Jul; 89 (7): 762-4 3. Hallal PC, Victora CG, Azevedo MR, et al. Adolescent physical activity and health: a systematic review. Sports Med 2006; 36 (12): 1019-30 4. Best TM, van Mechelen W, Verhagen E. The pediatric athlete: are we doing the right thing? Clin J Sport Med 2006 Nov; 16 (6): 455-6 5. Emery CA. Risk factors for injury in child and adolescent sport: a systematic review of the literature. Clin J Sport Med 2003 Jul; 13 (4): 256-68 6. Emery CA. Injury prevention and future research. Med Sport Sci 2005; 49: 170-91 7. Emery CA, Meeuwisse WH, McAllister JR. Survey of sport participation and sport injury in Calgary and area high schools. Clin J Sport Med 2006 Jan; 16 (1): 20-6 8. Backx FJG. Sports injuries in youth; etiology and prevention (thesis). Janus Jongbloed Research Center on Sports and Health, the Netherlands. Utrecht: Rijksuniversiteit Utrecht, 1991 9. van Mechelen W, Hlobil H, Kemper HC. Incidence, severity, aetiology and prevention of sports injuries: a review of concepts. Sports Med 1992 Aug; 14 (2): 82-99 10. Bartholomew LK, Parcel GS, Kok G, et al. Intervention mapping: designing theory and evidence-based health promotion programs. Columbus (OH): McGraw-Hill Higher Education, 2001 11. Kok G, Schaalma H, Ruiter RA, et al. Intervention mapping: protocol for applying health psychology theory to prevention programmes. J Health Psychol 2004 Jan; 9 (1): 85-98 12. Bartholomew LK, Parcel GS, Kok G. Intervention mapping: a process for developing theory- and evidence-based health education programs. Health Educ Behav 1998 Oct; 25 (5): 545-63 13. Marchi AG, Di Bello D, Messi G, et al. Permanent sequelae in sports injuries: a population based study. Arch Dis Child 1999 Oct; 81 (4): 324-8 14. Kujala UM, Kettunen J, Paananen H, et al. Knee osteoarthritis in former runners, soccer players, weight lifters, and shooters. Arthritis Rheum 1995 Apr; 38 (4): 539-46 15. Flynn JM, Lou JE, Ganley TJ. Prevention of sports injuries in children. Curr Opin Pediatr 2002 Dec; 14 (6): 719-22 16. Kelm J, Ahlhelm F, Pape D, et al. School sports accidents: analysis of causes, modes, and frequencies. J Pediatr Orthop 2001 Mar; 21 (2): 165-8 17. Hildebrandt VH, Ooijendijk WTM, Hopman-Rock M. Trendrapport: bewegen en gezondheid 2004-2005. Leiden: TNO Kwaliteit van Leven, 2007


18. SCP. Rapportage Sport 2006. The Hague: 2006 19. SCP. Rapportage jeugd 2002. Sociaal en Cultureel Planbureau, Den Haag, 2003 20. Kahl H, Dortschy R, Ellsasser G. Injuries among children and adolescents (1-17 years) and implementation of safety measures: results of the nationwide German Health Interview and Examination Survey for Children and Adolescents (KiGGS). Bundesgesundheitsblatt Gesundheits forsch Gesundheitsschutz 2007 May; 50 (5-6): 718-27 21. Schneiders W, Rollow A, Rammelt S, et al. Risk-inducing activities leading to injuries in a child and adolescent population of Germany. J Trauma 2007 Apr; 62 (4): 996-1003 22. Sundblad G, Saartok T, Engstrom LM, et al. Injuries during physical activity in school children. Scand J Med Sci Sports 2005 Oct; 15 (5): 313-23 23. Toet H, Schoots W, den Hertog PC, et al. Kosten van sportblessures in Nederland. Amsterdam: Consument en Veiligheid, 2005 24. Bartholomew LK, Parcel GS, Kok G, et al. Planning health promotion programs, an intervention mapping approach. San Fransico (CA): Jossey-Bass, 2006 25. Caine D, Caine C, Maffulli N. Incidence and distribution of pediatric sport-related injuries. Clin J Sport Med 2006 Nov; 16 (6): 500-13 26. Klassen TP, MacKay JM, Moher D, et al. Communitybased injury prevention interventions. Future Child 2000; 10 (1): 83-110 27. Machenbach J, van der Maas PJ. Volksgezondheid en gezondheidszorg. Maarsen: Elsevier Gezondheidszorg, 1999 28. Fishbein M, Ajzen I. Belief, attitude, intention and behavior: an introduction to theory and research. New York (NY): Wiley, 1975 29. Bandura A. Social foundations of thought and action: a social cognitive theory. Englewood Cliffs (NY): Prentice Hall, 1986 30. de Vries H, Dijkstra M, Kuhlman P. Self-efficacy: the third factor besides attitude and subjective norm as a predictor of behavioural intentions. Health Educ Res 1988; 3: 273-82 31. Kok G, de Vries H, Mudde A, et al. Planned health education and role of self-efficacy: Dutch research. Health Educ Res 1991; 6: 231-8 32. Verstappen FT, Twellaar M, Hartgens F, et al. Physical fitness and sports skills in relation to sports injuries: a fouryear prospective investigation of sports injuries among physical education students. Int J Sports Med 1998 Nov; 19 (8): 586-91 33. Emery CA, Cassidy D, Klassen TP. The effectiveness of a proprioceptive balance-training program in healthy adolescents: a cluster randomized controlled trial. Am J Epidemiol 2004; 159: 749-54 34. Heidt Jr RS, Sweeterman LM, Carlonas RL, et al. Avoidance of soccer injuries with preseason conditioning. Am J Sports Med 2000 Sep; 28 (5): 659-62 35. Hewett TE, Lindenfeld TN, Riccobene JV, et al. The effect of neuromuscular training on the incidence of knee injury in female athletes: a prospective study. Am J Sports Med 1999 Nov; 27 (6): 699-706 36. Junge A, Rosch D, Peterson L, et al. Prevention of soccer injuries: a prospective intervention study in youth amateur players. Am J Sports Med 2002 Sep; 30 (5): 652-9

Sports Med 2009; 39 (11)


37. Olsen OE, Myklebust G, Engebretsen L, et al. Exercises to prevent lower limb injuries in youth sports: cluster randomised controlled trial. BMJ 2005 Feb 26; 330 (7489): 449 38. Verhagen E, van der BA, Twisk J, et al. The effect of a proprioceptive balance board training program for the prevention of ankle sprains: a prospective controlled trial. Am J Sports Med 2004 Sep; 32 (6): 1385-93 39. Brug J, Schaalma H, Kok G, et al. Gezondheidsvoorlichting en gedragsverandering, een planmatige aanpak. Assen: Van Gorcum, 2001 40. Otis J, Lesage D, Godin G, et al. Predicting and reinforcing children’s intentions to wear protective helmets while bicycling. Public Health Rep 1992 May; 107 (3): 283-9 41. Berg P, Westerling R. Bicycle helmet use among schoolchildren: the influence of parental involvement and children’s attitudes. Inj Prev 2001 Sep; 7 (3): 218-22 42. Finch CF. Teenagers’ attitudes towards bicycle helmets three years after the introduction of mandatory wearing. Inj Prev 1996 Jun; 2 (2): 126-30 43. Miller PA, Binns HJ, Christoffel KK. Children’s bicycle helmet attitudes and use: association with parental rules. The Pediatric Practice Research Group. Arch Pediatr Adolesc Med 1996 Dec; 150 (12): 1259-64 44. Zahler L, Puhse U, Stussi C, et al. Active childhood-healthy life. Basle: Swiss Federal Office of Sports Magglinger


901

45. 46.

47.

48.

49.

(FOSPO); Institute for Exercise and Health Science, University of Basle, 2004 van Berkel M, Consten A, Danes H, et al. Basisdocument; bewegingsonderwijs. Zeist: Jan Luiting Fonds, 2004 Leyten C, Kemper H, Verschuur R. de MOPER hitheidstest: handleiding en prestatieschalen 9 t/m 11 jarigen. Haarlem: De Vrieseborch, 1982 Adam C, Klissouras V, Ravazzolo M, et al. Handbook for the EUROFIT test of Physical Fitness. Brussels: Council of Europe committee for the development of sport, 1988 Saunders RP, Evans MH, Joshi P. Developing a processevaluation plan for assessing health promotion program implementation: a how-to guide. Health Promot Pract 2005 Apr; 6 (2): 134-47 Dzewaltowski DA, Glasgow RE, Klesges LM, et al. RE-AIM: evidence-based standards and a Web resource to improve translation of research into practice. Ann Behav Med 2004 Oct; 28 (2): 75-80

Correspondence: Dr Mai J.M. Chinapaw, EMGO Institute and Department of Public and Occupational Health, VU University Medical Center, Van der Boechorststraat 7, 1081 BT Amsterdam, the Netherlands. E-mail: [email protected]

Sports Med 2009; 39 (11)

Sports Med 2009; 39 (11): 903-921 0112-1642/09/0011-0903/$49.95/0

REVIEW ARTICLE


Neuromuscular Adaptations to Training, Injury and Passive Interventions Implications for Running Economy Jason Bonacci,1,2 Andrew Chapman,1,3,4,5 Peter Blanch2 and Bill Vicenzino1 1 Musculoskeletal Pain and Injury Research Unit, University of Queensland, Brisbane, Queensland, Australia 2 Department of Physical Therapies, Australian Institute of Sport, Canberra, Australian Capital Territory, Australia 3 School of Kinesiology, Simon Fraser University, Vancouver, British Columbia, Canada 4 Applied Research Centre, Australian Institute of Sport, Canberra, Australian Capital Territory, Australia 5 Department of Kinesiology and Physical Education, McGill University, Montreal, Quebec, Canada

Contents Abstract. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. Literature Search . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. Adaptations of Muscle Recruitment to Single-Discipline Endurance Training . . . . . . . . . . . . . . . . . . . . 3. Adaptation of Muscle Recruitment to Multidiscipline Endurance Training . . . . . . . . . . . . . . . . . . . . . . . 4. Neuromuscular Characteristics and Running Economy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5. Training, Shoes, In-Shoe Orthoses, Musculoskeletal Injury and Running Economy. . . . . . . . . . . . . . . . . 5.1 Resistance Training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 Plyometric Training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 Stretching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4 Multidiscipline Sports and Training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5 Shoes and In-Shoe Orthoses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6 Musculoskeletal Injury. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7. Future Directions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Abstract

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Performance in endurance sports such as running, cycling and triathlon has long been investigated from a physiological perspective. A strong relationship between running economy and distance running performance is well established in the literature. From this established base, improvements in running economy have traditionally been achieved through endurance training. More recently, research has demonstrated short-term resistance and plyometric training has resulted in enhanced running economy. This improvement in running economy has been hypothesized to be a result of enhanced neuromuscular characteristics such as improved muscle power development and more efficient use of stored elastic energy during running. Changes in indirect measures of neuromuscular control (i.e. stance phase contact times, maximal forward jumps) have been used to support this hypothesis. These results suggest that neuromuscular adaptations in response

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to training (i.e. neuromuscular learning effects) are an important contributor to enhancements in running economy. However, there is no direct evidence to suggest that these adaptations translate into more efficient muscle recruitment patterns during running. Optimization of training and run performance may be facilitated through direct investigation of muscle recruitment patterns before and after training interventions. There is emerging evidence that demonstrates neuromuscular adaptations during running and cycling vary with training status. Highly trained runners and cyclists display more refined patterns of muscle recruitment than their novice counterparts. In contrast, interference with motor learning and neuromuscular adaptation may occur as a result of ongoing multidiscipline training (e.g. triathlon). In the sport of triathlon, impairments in running economy are frequently observed after cycling. This impairment is related mainly to physiological stress, but an alteration in lower limb muscle coordination during running after cycling has also been observed. Muscle activity during running after cycling has yet to be fully investigated, and to date, the effect of alterations in muscle coordination on running economy is largely unknown. Stretching, which is another mode of training, may induce acute neuromuscular effects but does not appear to alter running economy. There are also factors other than training structure that may influence running economy and neuromuscular adaptations. For example, passive interventions such as shoes and in-shoe orthoses, as well as the presence of musculoskeletal injury, may be considered important modulators of neuromuscular control and run performance. Alterations in muscle activity and running economy have been reported with different shoes and in-shoe orthoses; however, these changes appear to be subject-specific and nonsystematic. Musculoskeletal injury has been associated with modifications in lower limb neuromuscular control, which may persist well after an athlete has returned to activity. The influence of changes in neuromuscular control as a result of injury on running economy has yet to be examined thoroughly, and should be considered in future experimental design and training analysis.

Endurance sports such as running, cycling and triathlon are performed by many people at the recreational and competitive levels. At competition level, each of these sports requires extensive training. Triathlon is unique in that it is a multidiscipline sport requiring athletes to balance the training demands of three separate disciplines (i.e. swimming, cycling, running). The physiological and metabolic adaptations that occur in response to training have been extensively investigated. Oxygen consumption, blood lactate threshold, heart rate intensity, respiratory exchange ratio and the pulmonary ventilation threshold are common measures used to reflect endurance performance or adaptation to training.[1] ª 2009 Adis Data Information BV. All rights reserved.

The steady-state oxygen consumption at a given running velocity is defined as running economy,[2,3] and reflects the metabolic cost or metabolic demand of running. A strong relationship has been demonstrated between running economy and endurance running performance.[2,4-7] These measures highlight the relationship between the cardiorespiratory system and performance; however, they do not reflect the contribution of the neural system, which controls and coordinates human movement. The interaction between the neural and muscle systems (i.e. neuromuscular system) is fundamental to all movement, and effectively translates cardiorespiratory capacity into efficient movement and therefore into performance. Sports Med 2009; 39 (11)

Neuromuscular Adaptations and Running Economy

The neuromuscular system has the capability to adapt to training, not unlike the cardiorespiratory system. Studies over the past two decades have provided strong evidence that continued practice of a task (i.e. training) facilitates neuromuscular adaptations, which are characterized by more skilled control of movement and muscle recruitment patterns.[8-11] Traininginduced adaptations of descending motor commands reflect learning within the CNS and can be represented by changes in muscle electromyography (EMG) function (i.e. motor recruitment).[11] Like training, musculoskeletal pain and injury[12,13] – and passive interventions such as shoes and in-shoe orthoses[14-17] (which are often prescribed for pain and/or injury) – have been shown to induce acute adaptations in motor recruitment. Musculoskeletal overuse injury is a significant adverse effect of training that constitutes a major impediment to training and ultimately performance, through missed training and/or diminished training quality. The prevalence of lower extremity injury in recreational and competitive athletes ranges from 19.4% to 79.3% in running athletes[18] and 37–91% in athletes participating in triathlons.[19] An injuryinduced restriction in training can result in detraining, which may negatively affect performance, cardiorespiratory health and neuromuscular control.[20,21] It is apparent within the literature that training can induce positive changes in running economy.[22,23] Training also appears to induce adaptations in motor recruitment.[8,9,11] Less well known are the neuromuscular adaptations that occur with different modes of training (i.e. running, cycling, multidiscipline training, resistance training) and how these changes in neuromuscular control can be coupled with running economy. It has recently been hypothesized that improvements in running economy following strength and resistance training were due to neuromuscular adaptations.[24-26] Inferences have also been made that optimal lower limb muscle recruitment is critical for superior running economy.[27] However, these hypotheses have been based on indirect measures of neuromuscular control such as stance phase ground contact ª 2009 Adis Data Information BV. All rights reserved.

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times and leg strength during isolated tasks as evidence for neuromuscular adaptations. If neuromuscular adaptations are responsible for the changes in running economy then it would be reasonable to suggest that there would be alterations in motor recruitment during running following training. It is important to appreciate that adaptations in motor recruitment as a result of training represent a learning effect. Positive adaptations infer that an individual learns to produce specific patterns of muscle recruitment that are associated with optimal performance of the task. This is inherently different to the alterations in neuromuscular function that occur with fatigue during prolonged exercise.[28] Fatigue in itself is a complex phenomenon and much attention has already been directed toward better understanding the mechanisms of fatigue and regulation of output during endurance exercise.[29-32] Accordingly, the intent of this review is not to revisit this information nor discount the importance of fatigue in modulating exercise performance but rather to discuss the adaptations in motor recruitment (i.e. learning effects) that occur with different modes of training, injury and passive interventions and the implications this may have for running economy. Therefore, the aims of this review are to: (i) examine the adaptations of lower limb muscle recruitment (i.e. neuromuscular adaptations) to different modes of training (i.e. running, cycling, multidiscipline); (ii) examine what aspects of neuromuscular control are associated with running economy; and (iii) investigate whether neuromuscular adaptations induced by training, passive interventions and injury can be coupled with changes in running economy.

1. Literature Search The databases Cinahl, MEDLINE, PubMed, SportDiscus and Web of Science were searched using the following combination of terms: (‘running economy‘ or ‘oxygen consumption’ or . ‘VO2’) and (‘EMG’ or ‘muscle activity’ or ‘neuromuscular’) or (‘EMG’ or ‘neuromuscular’ or Sports Med 2009; 39 (11)

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‘running economy’ or ‘oxygen consumption’) and (‘orthoses’ or ‘orthotics’ or ‘shoes’ or ‘resistance training’ or ‘plyometrics’ or ‘injury’ or ‘cycling’ or ‘triathlon’). The reference lists of the articles obtained were searched manually to obtain further studies not identified electronically. All relevant studies in the English language were included.

2. Adaptations of Muscle Recruitment to Single-Discipline Endurance Training Motor learning studies have demonstrated that continued practice of a task results in more skilled control of movement, characterized by decreased amplitude and duration of muscle activity,[8-10] decreased muscle co-activation[9,11,33] and less variability of movement.[9,11,34] However, these studies examined novel hand and arm movements over a short training period (e.g. 1–2 days), and their results provide little insight into the adaptations of muscle recruitment that may occur in response to years of continued training by athletes. Furthermore, there is very little research that has directly measured the neuromuscular adaptations that occur in response to endurance training such as cycling and running, which involve repetitive, rhythmical actions. Initial studies comparing muscle recruitment patterns of trained cyclists to their novice counterparts presented conflicting findings and are limited by small sample sizes, EMG methodological limitations, and inadequate regard for kinematics (i.e. kinematics were not controlled or measured and any difference in EMG activity may have been due to kinematic changes).[35,36] Similarly, running studies[37,38] are hindered by the heterogeneity of participants and inadequate inclusion criteria, making it difficult to determine the specific training status of included athletes. Only recently has evidence emerged that trained cyclists and runners display different patterns of muscle recruitment to their novice counterparts. Novice cyclists with 1.4 – 0.4 years of cycling experience, who cycled 36.1 – 10.3 km/wk, exhibited greater individual variance (i.e. variability of muscle activity between pedal ª 2009 Adis Data Information BV. All rights reserved.

strokes for individual cyclists), greater population variance (i.e. variability of muscle recruitment between athletes), more extensive and more variable muscle co-activation and longer durations of muscle activity than highly trained cyclists with 10.2 – 1.4 years’ experience, cycling 393.9 – 32.5 km/wk[39] (figure 1[40]). A similar finding emerged when moderately trained runners (6.6 – 1.3 years’ experience, 61.4 – 8.8 km/wk) were compared with novice runners (3.4 – 2.8 km/wk).[41] Specifically, novice runners were characterized by greater individual variance (i.e. variability between strides) and greater population variance. These findings are consistent with previous short-term training studies of arm and hand movements,[8,9,33] suggesting that ongoing neuromuscular adaptations occur as a result of continued training. The cross-sectional nature of the cycling and running studies is a clear limitation. However, given the limitations of the aforementioned studies, and the difficulties of tracking athletes over many years of training, this is the strongest evidence of continuing neuromuscular adaptations to endurance training available at present. Trained triathlete

Trained cyclist

Novice cyclist

TA

TP

PL

GL

SOL 0°

180° 360° 0° 180° 360° 0° 180° 360° Crank angle Crank angle Crank angle

Fig. 1. Rectified electromyogram (EMG) of tibialis anterior (TA), tibialis posterior (TP), peroneus longus (PL), lateral gastrocnemius (GL), and soleus (SOL) muscles during cycling at 77.5 rpm. Data for ten non-contiguous pedal strokes from a representative highly trained triathlete, highly trained cyclist and novice cyclist are shown. EMG amplitude is shown as a percentage of the maximum measured amplitude (0–100%). Muscle activity is plotted for each complete pedal stroke from upper vertical position of the crank (0) through to a range of 360 (reproduced from Chapman et al.,[40] with permission).

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Neuromuscular Adaptations and Running Economy

3. Adaptation of Muscle Recruitment to Multidiscipline Endurance Training Multidiscipline endurance sports such as triathlon carry high training demands and are likely to provide an immense challenge to the human motor control system. Triathlon comprises sequential swimming, cycling and running, and triathletes often practice two or more of these disciplines in the one training session or practice each discipline separately with only short recovery periods (i.e. 2–4 hours). Short-term motor learning studies (i.e. 1–7 days of training) provide strong evidence that interference with acquisition of a new skill occurs when another task is practiced in sequence or within short interim periods.[42-45] Specifically, when multiple tasks are practiced in sequence or within short interim periods (i.e. 65 mL/min/kg; moderately trained = weekly running volume >30 km/wk; RE = run economy; recreational = weekly running volume 50% of ACL injuries occur in young athletes aged 15–25 years.[27,41-43] Knee injury prevention should be of even greater concern when it is considered that statistics on

1 These costs include both males and females with OA aged ‡30 years. OA data (incidence and costs) exclusive to sports knee injuries were not available even though an extensive database search was completed.[33]


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Knee Bracing in Preventing Knee Ligament Injury

return to sport post-injury, with conservative management and/or ACL reconstruction, illustrate a decreased level of participation, earlier forced retirement and/or continued knee joint discomfort. Following reconstruction, not all individuals return to their pre-injury level of competition, and those that do can expect up to 33% performance decrement compared with preinjury levels.[44,45] Roos et al.[46] found that only 30% of the ACL injured soccer players were active 3 years post-injury compared with 80% in an uninjured control population. The reason for this early departure from sport participation may be attributed to the fact that athletes who return to sport experience significant knee joint instability and a reduced range of motion and/or pain. As Myklebust and Bahr[47] stated, ‘‘It seems fair to conclude that, although the initial return rate is high, regardless of the treatment, previously injured athletes retire at a higher rate than athletes without previous ACL injury.’’ Furthermore, the above-listed medical costs and challenges do not account for the discomfort associated with long-term debilitating OA, which can affect the injured person’s professional, academic and/or private life.[23,38-40,48-52] Recently, the elevated risk of ACL injury in women, coupled with a 10-fold increase in US high school and a 5-fold increase in US collegiate sport participation in the past 30 years, has led to a rapid rise in the number of ACL injuries in female sports.[53,54] This increase in ACL injury in the female sports population has fuelled intensive research to identify the possible mechanism(s) responsible for high incidences of female knee injuries. However, despite the increased concern regarding the excessive number of ACL injuries in women, most orthopaedic literature on ACL reconstruction cites that more men than women experience an ACL injury and require ACL reconstructive surgery.[55] This ‘epidemic’ has prompted investigations aimed at identifying factors that will decrease knee injury severity and/or rates.[11,32] The initial ACL injuryprevention strategy had concentrated on enhancing the protection offered by the hamstring muscle group.[56-59] However, research has illustrated that this muscle group may be ineffective ª 2009 Adis Data Information BV. All rights reserved.

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in protecting the knee joint ligaments because of a delayed neuromuscular response.[60-65] In addition, the role of numerous other intrinsic and extrinsic risk factors as potential contributors to an ACL injury has been addressed by many researchers[26,29,32,61-63,66-108] and has led to the publication of more than 2000 scientific articles on ACL injuries in the past two decades.[109] Researchers agree that the findings on intrinsic risk factors improve our understanding of the mechanism(s) involved in ACL injury; however, widespread disagreement still remains regarding the effectiveness of prevention programmes aimed at both extrinsic and intrinsic ACL injury risk factors.[79,110-116] Thirty-six programme published papers were reviewed;[27,79,110-125] 24 studies reported a decrease in the rate of knee injuries in the intervention group[27,70,74,101,110,111,118-121,126-139] and 12 papers reported no effect of the respective intervention.[115-117,124,140-147] Hewett et al.[30] performed a meta-analysis of six randomized controlled trails or prospective cohort study prevention programmes[27,79,110,115,116,118] and concluded, ‘‘There is evidence that neuromuscular training decreases potential biomechanical risk factors for ACL injury and decreases ACL injury incidence in female athletes. However, we do not know which components [agility, balance, flexibility, plyometrics, proprioception, strengthening, training rate/intensity] are most effective or where their effects are combinatorial.’’ Nevertheless, as Griffin et al.[32] stated, ‘‘yone must appreciate that if anatomical [intrinsic] factors are found to be definitely associated with an increased risk of injury, they may be more difficult to modify than are environment, hormonal, and/or neuromuscular factors.’’ Griffin et al.[32] further stated, ‘‘The impact of ACL prevention programs is still largely unknown. More randomized controlled trails are needed between institutions, between various geographic areas of the country, across all age groups, and across both sexes for all high-risk sports, followed by a careful analysis of the effects of these prevention programs on influencing dynamic knee stability, sport performance, and overall injury rates.’’ It should also be noted that most prevention programmes have concentrated Sports Med 2009; 39 (11)

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on female athletes and have not addressed the high number of basketball non-contact ACL injuries for male athletes (60.3% for males vs 63.8% for females),[148,149] the high risk of contact ACL injuries in soccer for both sexes (46% for females and 58.7% for males),[18,19] and the high percentage of contact ACL injuries in collision sports such as football[13] and ice hockey.[4] In 1973, a paper on the first ‘functional knee brace’ (FKB) called the Anderson Knee Stabler (Omni Scientific Inc., Lafayette, IL, USA) to be worn in a sporting domain was published.[150] It was not until 1985 that the American Association of Orthopaedics Surgeons (AAOS)[151] sponsored a seminar to discuss the effectiveness of knee braces. From this seminar, three distinct brace classifications (rehabilitation, prophylactic and FKBs) were established;[150,151] these classifications are still used today (see figures 1–3). Rehabilitation braces are designed to allow a protected range of motion of injured knees post-surgery.

a

b

Fig. 1. Rehabilitation knee braces: (a) DonJoy, TROM Advance ¨ ssur, Innovator Rehab Knee Brace (permission to Cool and (b) O reprint kindly provided by DJO Inc., Vista, CA, USA and Ossur Americas, Orthopedics, Foothill Ranch, CA, USA).


Prophylactic knee braces (PKBs) are ‘off-the-shelf’ knee braces designed to prevent or reduce the severity of knee injuries. FKBs are custom-made braces that are designed to provide stability for unstable knees.[151,152] Despite much research having been conducted in the area of FKBs, the efficacy of these knee braces remains in question. Almost 20 years after their first meeting on knee bracing, the AAOS Position Statement was adjusted to reflect current research.[153] The AAOS[153] now stated ‘‘ywell-designed experimental studies have shown that currently available off-the-shelf prophylactic knee braces can provide at least 20% to 30% greater resistance to a lateral blow to the knee of sufficient magnitude to cause medial joint line opening. At least one well-designed clinical trial has revealed a statistically significant reduction in medical collateral ligament injuries with the use of a prophylactic knee brace.’’ The AAOS further stated that ‘‘ystudies designed to test whether FKBs protect against the knee ‘giving way’ have demonstrated some beneficial effect of the brace.’’[153] Despite the apparent preventive benefit(s), athletes remain reluctant to use a knee brace because of perceived impediment to performance.[52,153-157] The purpose of this literature review was twofold. First, to provide a synopsis of the current understanding of knee bracing, and second, to provide published evidence as to whether FKBing in non-injured individuals hinders performance. The following Internet search databases were employed to detect relevant articles: Evidence-Based Medicine Reviews, PubMed, SportDiscus, Ovid, MEDLINE and Proquest 5000. The search reference terms ‘knee injuries’, ‘bracing’, ‘knee bracing’, ‘functional knee bracing’ and ‘prophylactic knee bracing’ were used. In order to maintain the scientific integrity of the review process, the criteria for inclusion were that articles were originally published in peerreviewed scientific journals (n = 193), National Governing Body Reports (n = 6), and/or Clinical Symposia/Meeting Reports (n = 6). One submitted article, one article (with editor’s consent) that was not available on search databases, information from texts (n = 4), and one unpublished thesis were also cited. Sports Med 2009; 39 (11)


a

b

c

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d

e

f

Fig. 2. Prophylactic knee braces: (a) and (b) DonJoy, with unilateral hinged bar; (c) and (d) DonJoy, ACL Everyday, with bilateral hinged ¨ ssur, Paradigm with bilateral hinged bars; (f) O ¨ ssur, Trainer with unilateral hinged bar and strap (permission to reprint kindly bars; (e) O provided by DJO Inc., Vista, CA, USA and Ossur Americas, Orthopedics, Foothill Ranch, CA, USA).

1. Knee Bracing: 1970 to Mid-1990s During the 1970s, knee braces were used primarily for rehabilitation purposes. Devices such as the Lenox Hill brace (Lenox Hill Hospital Brace Shop, New York, NY, USA) were viewed as too bulky and restrictive during competition. Between 1979 and 1985, over 30 brace manufacturers introduced various knee braces that claimed to prevent medial collateral ligament (MCL) and ACL knee ligament injuries. Before 1985, accounts of the successes or failures of these devices were largely anecdotal.[158] After 1985, several studies focused on bracing effectiveness studies, cadaveric/surrogate model and subjective/objective study design. Research involving epidemiological and cadaveric/surrogate model study design tested the efficacy of PKBs in preventing knee ligament injuries. Studies involving subjective/objective methodology evaluated the PKB and the FKB effectiveness in preventing a MCL and/or ACL injury. The data obtained during the first 17 years allowed the AAOS to publish their first position paper on knee bracing.[151] This publication also fuelled knee bracing research, leading to 17 papers being published on this topic over the next 8 years. In the mid-1990s, with an increase in non-contact ACL injuries in female sports, researchers shifted their attention specifically to preventing noncontact ACL injuries and the role of knee bracing post-injury/surgery. ª 2009 Adis Data Information BV. All rights reserved.

1.1 Bracing Effectiveness Studies

Thirteen studies were reviewed, with ten studies[52,157,159-166] concentrating solely on MCL injury and the remaining three studies[9,167,168] on both MCL and ACL injury rates (see table I). Four studies reported no significant change in MCL knee injury rates,[163,164,166-167] whereas two studies a

b

¨ ssur, ExtremeLigament Fig. 3. Functional knee braces: (a) O Knee Brace, hinge, post, shell design, and (b) DonJoy, 4TITUDE, hinge, post, strap design (permission to reprint kindly provided by DJO Inc., Vista, CA, USA and Ossur Americas, Orthopedics, Foothill Ranch, CA, USA).

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Table I. Summary of bracing effectiveness studies using prophylactic knee braces Study (year)

Subjects

Brace type

Result(s)

Anderson et al.[160] (1979)

Nine professional American football players with knee injuries

Anderson Knee Stabler

Subjects played 29 games over two seasons without re-injury to the knee

Hansen et al.[161] (1985)

University of South California. 329 non-braced players and 148 braced players


Injury rate for non-braced players was 11% vs 5% for braced players

Schriner[162] (1985)

1246 high school players from 25 schools in Michigan

DonJoy, Cutter Anderson, Omni, McDavid Knee Stablizer

45 injuries from lateral blows in non-braced group vs 0 injuries from lateral blows in braced group

Hewson et al.[163] (1986)

University of Arizona. Non-braced (1977–1981): 28 191 IEs Braced (1981–1985): 29 293 IEs


No statistical difference in MCL injuries between the non-braced and braced periods

Rovere et al.[164] (1987)

Wake Forest University (1981–1984)


6.1% knee injuries during non-braced period and 7.5% knee injuries during braced period; data not statistically significant

Teitz et al.[159] (1987)

NCAA division 1 1984: 6307 players from 71 schools 1985: 5445 players from 61 schools

McDavid, Omni, Anderson Knee Stabler, Stabilizer, Don Joy, American Prostheses, others not specified

1984: 6.0% injury rate for non-braced vs 11% for braced players 1985: 6.4% injury rate for non-braced vs 9.4% for braced players. Significantly more MCL injuries for braced players

Grace et al.[165] (1988)

Albuquerque and Santa Fe high school players. 250 non-braced control group matched with 247 with single-hinge braces and 83 with double-hinged braces

Primarily McDavid Knee Stablizer and Stromgern

Knee injury rates: 1) non-braced = 4% 2) single-hinge = 15% significant › 3) double-hinged = 6%, statistically nonsignificant

Taft et al.[167] (1989)

University of North Carolina. (1980–1982) non-braced group (1983–1985) braced group

Anderson Knee Stabler and McDavid Knee Stablizer

No statistical difference in MCL, ACL or meniscal injuries between the non-braced and the braced periods

Sitler et al.[168] (1990)

1396 West Point Cadets playing intramural American Football

DonJoy Orthopaedics, Protector Knee Guard

Significant fl in total number of knee injuries and MCL injury in braced subjects Significant fl only noted in players playing a defensive position No significant fl in severity of MCL and ACL

Zemper[166] (1990)

Representation of NCAA and NAIA football teams/players: (1986) 32 teams with 3431 players (1987) 27 teams with 2798 players

Omni Anderson Knee Stabler (used by 37.5% of the subjects), DonJoy (20.5%), McDavid Knee Guard (20.6%), other unnamed braces (21.4%)

Total number of knee injuries observed: braced = 185 non-braced = 336 MCL injuries (based on 1987 data): braced = 32 non-braced = 69 severity of MCL injuries (based on 1987 data): MCL 1: braced = 21; non-braced = 41 MCL 2: braced = 8 non-braced = 22 MCL 3: braced = 3 non-braced = 6 Author concluded braces have no significant effect in reducing the severity of all knee injuries and specifically of MCL injuries Continued next page


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Table I. Contd Study (year)

Subjects

Brace type

Result(s)

Jackson et al.[9] (1991)

Professional Canadian Football League team (American Football): (1977–1983) non-braced group (1984–1988) braced group

McDavid Knee Stabilizer, Depuy, and Anderson Knee Stabler

No significant difference in number of injuries 17% significant fl in severity (>21-days lost) of knee injuries, 20% statistical fl in MCL injuries. No significant difference in ACL injuries

Albright et al.[52,157] (1994)

987 NCAA division 1 college football players, 50% braced

Unspecified

Found statistically significant lower rate of injury for braced vs non-braced players playing in ‘non-skilled’ positions

ACL = anterior cruciate ligament; IE = injury exposure; MCL = medial collateral ligament; NCAA = National Collegiate Athletic Association; › indicates increase; fl indicates decrease.

showed a significant increase in incidence of MCL knee injuries while using a PKB.[159,165] The remaining seven studies supported the use of a PKB for preventing MCL injures.[9,52,157,160-162,168] However, only four studies found a statistically significant reduction in MCL injury rates while using a PKB.[9,52,157,168] Of these four studies, Sitler et al.[168] and Albright et al.[52,157] stated that the statistically significant lower MCL injury rates pertained only to players playing in a defensive or in a ‘non-skilled’ position. All three studies concentrating on ACL injuries found no statistically significant difference between braced and nonbraced subjects.[9,167,168] 1.2 Cadaver and Surrogate Model Studies

Several studies have examined knee bracing from a biomechanical perspective using cadavers and surrogate models (see table II).[169-173] Paulos et al.[169,171] and France et al.[170] applied strain gauges to the bone of cadaver knees at attachment sites to determine the forces and joint openings necessary to disrupt the valgum, evaluating the restraining properties of ligaments in braced and unbraced knees. Forces were applied with a hydraulic apparatus and joint openings were measured with a single-axis electropotentiometer. Tests performed on the four braces showed that the mechanical stiffness (ability of a brace to absorb, distribute and transmit the input force and energy) varied 3-fold among the braces. The average stiffness of the unbraced knees at the point of ligament failure was equivalent to 105.8 kN/m ª 2009 Adis Data Information BV. All rights reserved.

compared with 25.1 kN/m for the braces alone. The resting tension in the MCL was increased in 60% of the braced knees, which was attributed to preloading of the ligament. Knees with a slight to moderate varus demonstrated as much as a 160% increase in ligament tension when braces were in place.[170,171] Hoffman et al.[172] reported that PKBs provided increased stability compared with unbraced knees with sectioned ACL and MCL. Baker et al.[173] presented similar data but only when FKBs were applied to the cadaver knee joint. 1.3 Functional Knee Brace Studies

In the 1984 AAOS seminar on knee braces, Paulos and colleagues[174] introduced a classification system for FKBs that included two basic types. The first consisted of the hinge, post and shell, while the second brace type consisted of the hinge, post and straps (see figure 3). The AAOS[151] used this classification for their position statement in defining available brace types. Research on FKB use concentrated on ACL-deficient and non-injured subjects in the following domains: subjective and clinical testing; kinematic testing; ground reaction force (GRF) testing; functional/game-related performance testing. 1.3.1 Subjective and Clinical Assessments

Subjective and clinical reports by brace users were another method employed by researchers to evaluate the efficacy of functional braces. Clinical-based assessments were the first to Sports Med 2009; 39 (11)

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Table II. Summary of cadaver and surrogate models using prophylactic knee braces Study (year)

Brace type

Evaluation

Findings

Paulos et al.[169] (1976)

Four unnamed braces

Applied strain gauges to cadaver knees to determine forces required for MCL disruption

› in resting ligament tension in braced knees, resulting in possible preloading of the MCL

Hofmann et al.[172] (1984)

3D 3-Way, 3D 2-Way, Bledsoe, Universal, ‘Anatomic’ Universal, Knee-Trol

Measurements (displacement) taken by using half pins and an external fixator to the tibia and femur. Tested for anterior, valgus, and rotational stability

All braces provided › in stability compared with non-braced knees with a sectioned ACL and MCL, but did not duplicate natural ligamentous stability

Baker et al.[173] (1987)

2 PKB: Anderson Knee Stabler, McDavid Knee Guard Also tested 5 FKB, results presented in table III

Force transducers applied to the MCL and ACL. Abduction forces (0–30 N) were applied. Data collected at 0, 15 and 30 of knee flexion

No reduction in knee abduction angle with PKB use. With unstable MCL, different braces offered varied protection

Paulos et al.[171] (1987)

McDavid Knee Guard and Omni Anderson Knee Stabler

Conducted static non-destructive (1 mm/sec) and low-rate destructive (76–90 mm/sec) valgus loading. Medial joint opening and ligament injury mechanisms in cadaver knees measured

MCL disruption at higher tensions than ACL and PCL. MCL provided 80% medial restrain, ACL 11%, PCL 9%. Braces tested did not offer protection. Four potential adverse effects reported: (1) MCL preloading, (2) centre axis shift, (3) premature joint line contact, (4) brace slippage

France et al.[170] (1987)

McDavid Knee Guard, Omni Anderson Knee Stabler, DonJoy Knee Guard, Stromgren brace, Mueller brace, and the True-Fit Renegade

Using a surrogate knee model, performed 500 impact tests with and without a knee brace. Knee joint was in full extension or flexed to 30. Limb was in constrained or unconstrained position. Used two valgus impact loads that caused 7 mm (start of MCL damage) and 15 mm (MCL disruption) joint opening. Lateral impact loads of to evaluate: (1) pre-loading, (2) brace performance, (3) ideal brace characteristics

(1) MCL preloading negated by joint compressive forces; (2) one brace exceeded the minimum impact safety factor; (3) ‘ideal’ brace should › lateral absorption rate by 80%

ACL = anterior cruciate ligament; FKB = functional knee brace; MCL = medial collateral ligament; PCL = posterior cruciate ligament; PKB = prophylactic knee brace; › indicates increase.

illustrate statistically significant reduction in anterior tibial displacement and rotatory instability in braced ACL-deficient subjects.[175-177] However, all studies were conducted using low forces and concerns were raised regarding the efficacy of FKBing during application of higher forces to the braced ACL-deficient knee joint. The subjective studies (usually a collection of responses to set questions) gave insight into the capability and the acceptability of the brace(s) being tested by the wearer. Whether these subjective reports were reflective of decreased knee laxity or of performance remain inconclusive, as indicated in table III. 1.3.2 Kinematic Testing

The earliest kinematic studies on ACLdeficient subjects concentrated analysis on three rotations about the knee joint with the use of a ª 2009 Adis Data Information BV. All rights reserved.

3-degrees-of-freedom electrogoniometer. However, the electrogoniometer had inherent restrictions imposed by the electronic cable, the ‘umbilical cord’ between the device and recording unit.[179-183] Three studies used an electrogoniometer to measure three rotations between ACL-deficient and healthy control subjects during running.[181-183] All three studies reported flexion and total varus/valgus motion to be greater in the ACLdeficient group, while internal-external rotation was less. However, none of the differences were found to be statistically significant.[181-183] In an unnamed study identified in Branch and Hunter’s paper,[179] walking analysis was completed on 20 ACL-deficient and 30 control (non-injured) subjects using a goniometric technique whereby 6 degrees of freedom were measured. The results showed no statistical difference between the three Sports Med 2009; 39 (11)


groups in flexion-extension, varus-valgus, internalexternal rotation, medial-lateral shear or joint compression-distraction. However, statistically significant increases in anterior translation were noted (mean difference of 4.7 mm). Unfortunately, the authors did not provide KT-1000 (MEDmetric Corporation, San Diego, USA) arthrometer measurements (knee joint laxity) or make clear at which walking and/or running phase(s) the increase occurred. This study was replicated using high-speed cinematography and focused on walking, running and stair climbing.[184] Tibone and colleagues[184] reported that the results failed to show any statistical differences. Branch and others[185] (mentioned in Branch and Hunter[179]) using a 3-dimensional tracking system measured compensatory kinematic changes between ACL-deficient subjects and healthy subjects during a side-step manoeuvre. The ACL-deficient subjects kinematics were also analysed using the strap-type DonJoy brace and the shell-type CTi brace. The authors reported that the ACLdeficient group exhibited greater anterior shift of their pelvis, kept their hips less abducted and were more externally rotated during the stance phase compared with non-injured control subjects.[179] Furthermore, the ACL-deficient subjects planted side knee was in greater varus and externally rotated while the ankle was also more externally rotated than the control group. Branch and Hunter[179] concluded that the cumulative external rotation of the hip, knee and ankle in the ACLdeficient group translates to a compensatory early turning of the body towards the cut. However, the data were not statistically significant. As a result, the authors suggested that persons with ACLdeficiency employ a complex set of kinematic adjustments to compensate for knee laxity and thus the above measures may be statistically significant as a set but not individually. Even though the above data were not statistically significant, the authors illustrated that knee brace during running produced statistically significant decreases in knee flexion (22% in the sagittal plane) during the swing phase and 13% during the stance phase. Further-

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more, a 24% reduction in mediolateral/varus-valgus movements as well as a 35% reduction in total tibial rotation was reported. DeVita et al.[186] assessed the biomechanical effects of an FKB2 on kinematics, GRFs and joint moments during the stance phase of running. Two groups were tested, non-injured subjects and ACL-deficient subjects. The latter group was tested with and without an FKB while the non-injured subjects were only tested without the brace. Kinematics analysis exhibited the following results: Bracing did not alter knee kinematics. In comparison with ACL-deficient subjects, non-injured subjects flexed about 8 and 11 more at the hip and knee, respectively, throughout the stance phase. The ACL-deficient group adopted a more erect running style. Vailas and Pink[187] compared performance levels using an unnamed FKB and a placebo knee sleeve on non-injured and ACL-deficient subjects. Statistically significant decreases in torque were found in braced non-injured subjects. Braced ACL-deficient subjects exhibited less torque on the involved limb than on the uninvolved limb. However, no statistical differences were found when the placebo knee sleeve was used by either group and between the braced and unbraced ACL-deficient limb. The authors suggested FKB provided some mechanical restraint to the entire lower extremity instead of just the knee joint. In light of these findings, the authors stated that an FKB should be considered for persons with significant functional ACL deficiency. 1.3.3 Ground Reaction Force Testing

Tibone and colleagues[184] tested 20 subjects with a minimum grade 1+ ACL knee joint laxity (as defined by Arnheim[188]) identified by positive Lachman, anterior drawer, pivot shift and KT1000 testing. Significantly greater vertical GRFs were reported for the involved limb during fast walking and a significantly higher roll-off vertical GRF were noted in the uninvolved limb during

2 Specific knee brace name and manufacturer was not provided. The brace was a strap design and had bilateral posts. The mean weight of the braces was 8.0 N (800 g).


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Table III. Summary of subjective and clinical assessment using functional knee braces Study (year)

Brace type

Evaluation

Findings

Nicholas[150] (1973)

Lenox Hill

52 ACL-deficient subjects

65% of brace users reported instability and not able to return to pre-injury sport

Bassett and Fleming[175] (1983)

Lenox Hill

36 ACL-deficient subjects evaluated anterior drawer and ALRI/AMRI. Subjects also provided subjective feedback

Brace use improved anterior drawer by minimum 1 grade in 81% of the subjects, ALRI improved in 50% of the subjects. Subjectively, 70% of the subjects reported episodes of giving way while wearing the brace; 5% in daily living activities, 8% in recreational sports

Colville et al.[176] (1986)

Lenox Hill

45 ACL-deficient subjects completed clinical tests and provided subjective feedback

Brace failed to significantly fl maximal anterior tibial subluxation. Rotatory instability improved 1 grade with brace use, while varus/valgus laxity remained unchanged. Subjectively, brace use significantly fl episodes of giving way and 69% of subjects reported improved athletic performance. Overall, 91% described the brace as being beneficial

Baker et al.[173] (1987)

DonJoy, Generation II PoliAxial, Lenox Hill, PRO-AM, CTi. Also tested 2 PKBs, results presented in table II

Force transducers applied to the MCL and ACL. Abduction forces (0–30 N) were applied. Data collected at 0, 15 and 30 of knee flexion

A reduction in knee abduction angle with FKB use

Mishra et al.[178] (1989)

Don-Joy Four-Point, RSK, Lenox Hill, and CTi

42 ACL-deficient subjects evaluated by clinical exam and KT-1000 testing. Subjects had used a brace for 1 month

Subjects reported brace migration greatest concern; fl in pain and swelling episodes with brace use. Authors found subjects continued same pre-injury sport participation but for shorter duration

Rink et al.[177] (1989)

CTi, OTi, and Omni TS7

14 subjects arthroscopically proven and conservatively managed ACL. Subjects used each brace for 180–240 hours over 1 month

Subjects reported statistically significant fl in knee instability and pain level with improved activity level; each subject preferring a different brace. Low force KT-1000 tested in significant reduction in anterior tibial displacement

ACL = anterior cruciate ligament; ALRI = anterolateral rotatory instability; AMRI = anteromedial rotatory instability; FKB = functional knee brace; MCL = medial collateral ligament; PKB = prophylactic knee brace; fl indicates decrease.

running. The authors suggested that the increased force during fast walking was an attempt to minimize forces across the ACL-deficient knee joint. The decreased force on the involved knee joint was thought to be related to a midstance subluxation episode. During both the cross-cut and the side-step cut/open cut3 manoeuvres, decreased lateral shear was noted in the injured limb. In addition, vertical force was significantly lower during the side-step test, whereas the antero-

posterior shear was statistically lower during the cross-cut movement. Tibone and colleagues[184] attempted to factor the multiple techniques used to negotiate a cut without subluxing the knee joint by employing a non-dimensional parameter called the ‘cutting index’4 and found significant differences between ACL-deficient and healthy knee joints. The authors suggested that subjects with ACL deficiency utilize a slower approach to the cut, spend more time in the stance (plant)

3 Side-step/open cut involves planting with the reference limb (i.e. the injured limb) and cutting away from the planted limb. ðYÞ ðZ FORCESÞ ðAPPROACH ANGLEÞ 4 Cutting index defined:[184] ðTIMEðXÞ ON FORCE PLATFORMÞ ðAPPROACH TIMEÞ ª 2009 Adis Data Information BV. All rights reserved.

Sports Med 2009; 39 (11)


phase of the cut, reduce the angle of the cut and exert less force on the planted leg during the cut. Replicating the study using a custom fitting shelltype FKB (CTi), Cook and colleagues[189] reported the braced ACL-deficient limb had significantly greater shear forces when compared with the same limb unbraced. Furthermore, running velocity increased while wearing an FKB for most athletes, but this result was not statistically significant. As a result, Cook et al.[189] suggested that FKBs allow for significantly better running and cutting performances for athletes with an injured ACL. DeVita et al.[186] reported that an FKB did not affect the GRFs of ACL-deficient subjects running on a flat surface. Persons with ACL deficiency had greater maximum impact force in both conditions (braced and unbraced) than noninjured runners; however, the differences were not statistically significant.

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Five studies reported no significant differences between braced and non-braced groups,[177,178,185,194-195] whereas four studies reported statistically inferior performance measures.[196,197,200-201] Marans et al.[198] found ACLdeficient braced subjects had statistically inferior performance levels in the 40 m sprint but statistically superior performance in the figure-of-eight test. Veldhuizen et al.[199] described that braced subjects had statistically inferior performance levels on the first day of testing, but by day 28, performance was no different between the two testing conditions. However, the continued notion that knee brace use during athletic activity may impair performance by disrupting normal neuromuscular control[179] may be alleviated by the suggestion that brace accommodation is required in order to circumvent neuromuscular disruption and facilitate relearning; otherwise, the brace wearer may risk injury.[3]

1.3.4 Sport-Related Performance Testing

An alternative method to evaluate functional bracing is to examine its impact on athletic performance. Of the first studies to investigate the effect of bracing on motor performance, Corcoran et al.[190] and Reed[191] reported an improvement in walking speed. Both studies, however, were performed with hemiparetic and arthritic subjects, which is only remotely related to athletics and bracing. To date, objective measurement of knee function during athletic performance has been limited to oxygen consumption/expenditure, timed tasks and/or distances during isolated athletic activity (see table IV). Performance assessment has been divided into two categories: either specific running5[179,202] or jumping6[179,202,203] activities. Thirteen studies were examined. The first study used 6 kg weights on each foot while walking at 5.49 km/h and reported a 420% increase in energy expenditure,[192] while Houston and Goenans[193] reported no differences in lower extremity isometric and dynamic strength. However, no statistical analyses were performed in either study.

1.4 Summary of Knee Bracing: 1970 to Mid-1990s

Many brace-effectiveness studies lacked an adequate subject pool to obtain statistically significant results. Other studies had high variance, as the large subject pool had no control population, and were designed to diagnose and/or treat injuries. Furthermore, many studies did not calculate exposure and injury rates and most did not measure knee laxity and/or account for previous injury prior to knee bracing, which could result in higher risk of injury or re-injury. Lastly, some studies did not perform statistical analysis. Although cadaver and surrogate studies provide us with excellent information, the results cannot be equated to on-field performance. There are many other factors (proprioception, reflexes, muscular stability and the athlete’s anticipation to contact) that may help an athlete to avoid serious injury. One study raises the issue regarding validity. Paulos et al.[171] suggested that the

5 Category 1 specific tests include 40-yard dash, shuttle run, figure-of-eight run, stair climb, slalom circuit and cross-cut manoeuvre.[179,202] 6 Category 2 specific tests include one-leg long (horizontal) jump and vertical jump.[179,202,203]


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Table IV. Summary of sport-related performance testing using various knee braces Study (year)

Brace type

Evaluation

Findings

Soule and Goldman[192] (1969)

6 kg weight on each foot

Walked at speeds of 5.49 km/h

420% › in energy expenditure compared to non-weighted walking

Houston and Goenans[193] (1982)

PKB: Lenox Hill, Toronto 2191 and The Kelly

Seven subjects: three with MCL instability, one ACL-deficient, and three with combined ACL and MCL injury. Performed four functional tests (isometric, isokinetic, and maximal knee extension strength tests, stationary bicycle endurance test) over 4 weeks

Isometric strength test, no difference. Dynamic strength testing at 30/sec, braced limb slower; at 300/sec and maximum angular velocity 12–30% slower. Authors concluded that braced subjects were slower, produced less power and produced 41% more lactic acid

Iglehart[194] (1985)

FKB: CTi

Ten non-injured subjects. Three tests performed and three testing sessions; day 1, brace provided, after 280–420 hours of use, after 420–630 hours of brace use

Authors suggested CTi brace use led to no statistical effect on strength and/or motor performance

Tegner and Lysholm[195] (1985)

PBK: ECKO

26 subjects with ACL deficiency and 16 subject post-ACL reconstruction

No significant difference between two groups. › in hop index reported in braced ACL-deficient group; authors suggested was due to › in confidence

Zetterlund[196] (1986)

FBK: Lenox Hill

Ten arthroscopically confirmed ACLdeficient subjects. Subjects used an FKB an average of 23.9 months. Performed treadmill running

After 6 minutes of treadmill running, braced subjects had significantly › levels of oxygen consumption (5.3%) and heart rate (4.3%). No significant difference in ventilation or stride length between the two conditions

Mishra et al.[178] (1989)

4 FKBs used (Don-Joy FourPoint, RSK, Lenox Hill, and CTi)

42 ACL-deficient subjects evaluated by clinical exam and KT-1000 testing. Subjects had used a brace for at least 1 month. Performed 1-legged hop jump and 40-yard shuttle run

Brace use led to fl in the measured pathologic anterior displacement. Improved performance in hop jump only, but not statistically significant

Rink et al.[177] (1989)

2 FKBs (CTi and Omni TS7)

14 arthroscopically proven ACLdeficient subjects performed a figureof-eight test

No significant difference in timed performances in 20-yard and figureof-eight between the two conditions. Authors reported five subluxation episodes with brace use and concluded that there was no advantage to bracing

Unpublished study reported by Branch and Hunter[185] (1990)

FKB: CTi

Ten non-injured subjects used brace for 336 to 420 hours and performed 5 tests.

No statistically significant difference between braced and non-braced conditions

Highgenboten et al.[197] (1991)

4 FKBs (Generation II PoliAxial, Orthotech Performer, CTi, and Lenox Hill Derotation)

14 asymptomatic subjects performed six treadmill runs, at speeds of 9.5 to 12.8 km/h, over 2 weeks.

Significant › in oxygen consumption, heart rate, ventilation between 3% and 8% and › in RPE by 9% and 13%. No data on accommodation over the 2-week testing period

Marans et al.[198] (1991)

6 FKBs (DonJoy Four Point, DonJoy Rotational, Generation II Poly-Axial, Lenox Hill Derotation, McDavid Knee Guard, and Zimmer Double Hinged)

Ten subjects with arthroscopically proven ACL-deficient knee joints. Subjects performed six functional tests

Braced performance level was significantly slower during in the 40 m sprint but faster during figure-of-eight and acute-angle cutting (slalom) tests. Results were brace dependent

Continued next page


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Table IV. Contd Study (year)

Brace type

Evaluation

Findings

Veldhuizen et al.[199] (1991)

PKB: Push Brace Heavy

Eight healthy subjects performed four tests over four durations: (1) 3 days pre-brace application; (2) day 1 of brace use; (3) 28 days after first day of brace use; (4) 1 day post-brace use

Statistically lower performance levels on day 1 of brace use for all tests and no difference after using the brace for 28 days. 1 day after brace removal all test parameters were statistically similar to base values

Styf et al.[200,201] (1992 and 1999)

DonJoy Hinged Neoprene Knee Support, Omni II, and Bell-Horn Knee Sleeve

Eight non-injured subjects used to evaluate brace use and intramuscular pressure

Statistically significant › in intramuscular pressure with use of all three braces

ACL = anterior cruciate ligament; FKB = functional knee brace; MCL = medial collateral ligament; PKB = prophylactic knee brace; RPE = rate of perceived exertion; › indicates increase; fl indicates decrease.

ACL and the posterior cruciate ligament (PCL) disrupt prior to the MCL being torn during valgus loading. However, if this were true, during valgus loading the MCL should never sustain an isolated injury. Also, since the medial meniscus is attached to the MCL, it should not sustain injury during isolated valgus loading. As such, the testing conducted by Paulos and colleagues must have had some limb rotation. All presented studies based on subjective reporting had similar findings. Furthermore, all studies were conducted with high reliability. All performance dynamic/game-like testing research, except that done by Cocorran et al.[190] and Reed,[191] has been conducted with high validity. Of these studies, three provided the greatest insight into how a functional brace may perform during competition.[197,198,201] The one criticism of these studies is that they focused on product testing (of available braces) rather than strictly on athletic performance. Kinematic data has been very valuable as it has allowed researchers to visualize how body segments behave in a particular segment of time. As with kinematic research, force platform studies have also provided excellent visual information on the GRF encountered by the injured or non-injured and the braced and non-braced limbs. Over the last 25 years, the evidence from the review of the literature suggests that FKBs for ACL deficiency may mediate improvements in knee stability and mobility when performing activities of daily living and during certain sporting activities. However, the efficacy of FKBs in preventing knee joint ligament injury remains ª 2009 Adis Data Information BV. All rights reserved.

inconclusive. Few studies have investigated whether apprehension about wearing a brace during athletic activity impairs performance and consequently leads to non-compliance, and this warrants further investigation. 2. Knee Bracing: Mid-1990s to Present By the mid-1990s, female participation in US collegiate and high school athletics experienced a respective 5- to 10-fold increase, with concomitant increases in ACL injuries.[53,54] During the same time period, a rapid rise in ACL injuries in female sports was noted.[53,54] This fuelled intense ACL research in three specific areas: 1. identifying the mechanisms responsible for the high incidences of non-contact knee ligament injuries; 2. investigating the potential benefit of FKBing for ACL deficiency; 3. investigating whether FKBs are beneficial post-ACL reconstruction. In a survey of brace prescription patterns, 97% of orthopaedic surgeons reported that they prescribe braces to their ACL-deficient and ACLreconstructed patients,[204,205] many of whom continue to report positive subjective feedback with their use.[155,177,178,198,206-208] The lack of supportive scientific evidence that FKBs may be beneficial during athletic participation[155,206-211] or prevent knee ligament injuries remains contentious.[32,204,208,210-213] Moreover, the biomechanical evidence on the effects of PKBs on preventing MCL injury remains ambiguous.[156,214] Sports Med 2009; 39 (11)

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2.1 Knee Bracing Studies

Of the 15 studies analysed, seven evaluated knee brace use on subjects with ACL deficiency,[104,215-220] three assessed brace performance after ACL reconstruction,[221-223] and the remaining five tested brace use on non-injured subjects[212,224-227] (table V). These five studies used non-injured subjects; one used a ‘sleeve-type brace’,[224] the second study did not perform functional/dynamic testing,[212] the third used an unnamed PKB,[226] the fourth study evaluated a newly designed functional brace,[227] and the fifth screened over 9000 professional skiers to evaluate the potential benefit of bracing.[225] However, none addressed the effectiveness of an FKB to possibly prevent a ligament injury and/or the impact on performance hindrance. Of the seven studies involving braced ACL-deficient subjects, five reported statistically improved performance levels,[217-220,228] whereas two reported no performance differences between nonbraced and braced ACL-deficient groups.[215,216] Performance differences were no different between ACL-reconstructed braced and non-braced groups.[221,223] Wu et al.[222] suggested that both FKB- and placebo-braced subjects may have improved static knee joint proprioception but not muscle functioning. Of the five studies that examined braced non-injured subjects’ performance levels, one recorded an 11% improvement in joint proprioception[224] and one found that braced subjects exhibited significantly reduced anterior shear loads.[212] Kocher et al.[225] found that a significantly higher proportion of non-braced skiers sustained an ACL injury and they had a higher risk of re-injury post-ACL surgery when not wearing a brace. Culp et al.[226] observed that although PKBs have no proprioceptive benefits, they may assist in absorbing externally applied forces. The study by Yu et al.[227] found a newly designed FKB had no effect on peak ground reaction forces during the stop-jump task. 2.2 Functional Knee Bracing and Game-Related Performance Testing

Three studies investigated FKBing on noninjured subjects (see table VI). ª 2009 Adis Data Information BV. All rights reserved.

Stephens[229] found no statistical differences in straight line and successive turning running activities among collegiate basketball players using two different FKBs. Two studies evaluated athletes’ speed and agility,[154,215] and one study measured brace tendency to migrate (brace movement in the horizontal and/or vertical planes) in dynamic/game-like settings.[154] Testing six FKBs during the 40-yard dash (speed) and the fourcone drill (agility) tests, the authors[154] reported that performance levels were statistically hindered while using two of the six FKBs in the speed test. During the agility drill, performance levels decreased only when wearing one of the six FKBs, leading Greene et al.[154] to suggest that FKBs do not significantly reduce speed and agility. However, all braces tended to migrate, potentially affecting protective function and athletic performance. To investigate whether braces worn during athletic activity hindered performance, 30 non-injured subjects performed five functional tests with and without an FKB.[215] During the brace accommodation phase, the braced group demonstrated statistically inferior performances during the 10 m dash, figure-of-eight and slalom tests, and a statistically superior performance in the horizontal hop test. When running down stairs, no statistical differences were noted between conditions. However, once subjects had accommodated to the brace (best performance measures), no significant differences were noted between the braced and non-braced conditions for any of the tests.[215] 2.3 Summary of Knee Bracing: Mid-1990s to Present

According to Marans et al.,[198] the degree of objective instability found by clinical testing has never been correlated to the degree of functional instability (instability during daily and sporting activities) that one experiences as a result of an ACL injury. While many studies have concentrated their research on the effectiveness of one type of brace or on a comparison between available braces,[198] or have focused on ACLdeficient subjects or subjects with surgically reconstructed ACLs,[230] these studies have Sports Med 2009; 39 (11)


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Table V. Summary of knee brace studies, mid-1990s to present Study (year)

Brace type

Evaluation

Findings

McNair et al.[224] (1996)

Knee sleeve type brace

20 subjects with no musculoskeletal or neurological deficit performed tracking task on Kin-Com. Angle and force data sampled using electrogoniometers

Improvement of 11% in tracking while using the knee sleeve

Wojtys et al.[228] (1996)

Six FKBs (Bledsoe Proshifter, Generation II, Poli-Axial, Lenox Hill Spectralite, Townsend, Sutter Telon, CTi)

Five arthroscopically confirmed ACL-deficient subjects. Assessed effects of FKBs on anterior tibial translation, isokinetic performance and neuromuscular function

Braced subjects had significantly fl anterior tibial translation with and without muscle activation. Also, spinal level reaction time improved for quadriceps but not for hamstrings

Risberg et al.[221] (1999)

DonJoy rehabilitation brace followed by FKB, DonJoy Gold Point

60 subjects post-ACL reconstruction followed for 2 years. 30 subjects per braced and non-braced group. Measured knee laxity, Cincinnati knee score, ROM, thigh atrophy, isokinetic testing, three functional knee tests, and visual analog scale to evaluate pain

No significant disparity in knee joint laxity, ROM, muscle strength, functional knee testing, or pain between groups. Cincinnati score showed significantly › functioning at knee function at 3-month follow-up even with significant thigh atrophy

Fleming et al.[212] (2000)

FKB: DonJoy Legend

15 non-injured subjects with arthroscopically proven intact ACL. Evaluated the ACL strain response in braced and unbraced knees during nonand weightbearing in combination with (1) anterior-posterior shear forces, (2) internal-external torques, and (3) varusvalgus moments external applied loads.

1) A-P forces: Brace significantly fl strain on anterior shear loads up to 130 N during non- and weightbearing 2) I-E torques: Braced knee had statistically fl strain (up to 9 Nm) in nonweightbearing 3) Brace did not significantly fl external (up to 9 Nm) and varus-valgus (up to 10 Nm) moments

Rishiraj et al.[215] (2000)

FKB: Generation II PoliAxial

30 ACL-deficient (grade 2, KT-1000 evaluated) subjects. Subjects performed five functional tasks

Braced group performance › by 1.1–6.5% in speed and agility events and 1.8–4.4% in the hop test. Results were statistically non-significant

Wu et al.[222] (2001)

FKB: DonJoy Legend and a mechanical placebo brace

31 subjects post-ACL reconstruction, minimum 5 months post-surgery. Evaluated subjects’ ability to accurately reproduce specified knee joint angles and knee joint isokinetic performance at 60 and 180/sec

Compared with non-braced, braced and placebo braced subjects may improve static knee joint proprioception but not muscle functioning.

Ramsey et al.[216] (2001)

FKB: DonJoy Legend

Six ACL-deficient subjects evaluated with grade 2 Lachman test and KT-1000 testing results of 4.5–9.0 mm. Assessed knee kinematics during horizontal hop jump using Steinmann traction pins

Bracing produced minor and inconsistent reduction in anterior tibial translations during hop jump

Beynnon et al.[217,218] (2002 and 2003)

Two FKBs: DonJoy Legend, SofTec Genu and Townsend Rebel

Nine subjects with chronic ACL-deficient knees. A-P shear and compressive loads applied to the knee, and tibial translation measured in nonweightbearing, throughout the transition to weightbearing, and during weightbearing

Bracing resulted in a significant fl of A-P laxity values, to within limits of the normal knee during non-weightbearing and weightbearing postures, but not during transition from nonweightbearing to weightbearing. Latter anterior translation › 3.5 times more than in the normal knee

Kocher et al.[225] (2003)

Various knee braces, specific names not identified

9410 professional skiers screened (1991–1997) and 180 ACL injuries reported. ACL-deficient knee was defined by an abnormal Lachman or

Significantly higher proportion of non-braced skiers sustained ACL injury. Risk ratio of 6.4 (13% and 2%, respectively) for subsequent knee Continued next page


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Table V. Contd Study (year)

Brace type

Evaluation

Findings

pivot-shift and a 5 mm or greater KT-1000 manual maximum laxity

injury between non-braced and braced skiers. Univariate analysis revealed no significant effects of the other covariates Significant › in rectus femoris activity on landing only one subject demonstrated › anterior drawer. Authors suggested joint stability may result from proprioceptive feedback rather than the mechanical stabilizing effect of the brace

Ramsey et al.[219] (2003)

FKB: DonJoy Legend

Four ACL-deficient subjects with +2 Lachman performed horizontal hop jump. Recorded EMG and simultaneous tibiofemoral kinematics data to investigate the effect of the brace

Smith et al.[220] (2003)

FKB: CTi

Ten individuals with chronic ACL-deficient knee performed three single-leg hop manoeuvres on their ACL-deficient knee with and without a knee brace. Recorded EMG data

Brace significantly delayed average vastus lateralis onset before landing. Non-braced, 5 of the 10 subjects activated hamstrings or gastrocnemius muscles first. Braced, 7 of 10 activated same muscles first. Authors suggested multiple strategies may exist to stabilize the braced ACL-deficient knee

Culp et al.[226] (2004)

PKB: unnamed

20 non-injured males performed repeated double leg squats, held position for 10 sec and repeated movement to failure

Prophylactic knee bracing had no proprioceptive affect on the knee. Authors concluded, bracing may absorb external loads

McDevitt et al.[223] (2004)

FKB: DonJoy IROM

100 subjects post-ACL reconstruction followed for 2 years. Braced group used brace post-surgery. Non-braced and braced data collected during cutting, pivoting, jumping and strength test activities

No significant difference in knee stability between groups in single-leg hop test, Lysholm scores, knee ROM or isokinetic strength testing. Two braced and three non-braced subjects reinjured ACL

Yu et al.[227] (2004)

FKB: Newly designed DonJoy 4titude

20 non-injured subjects. Performed non-braced and braced stop-jump task

New knee brace fl knee flexion by 5 but did not significantly affect peak ground reaction forces while performing a stop-jump task

ACL = anterior cruciate ligament; A-P = anterior-posterior; EMG = electromyogram; FKB = functional knee brace; MCL = medial collateral ligament; PKB = prophylactic knee brace; ROM = range of motion; › indicates increase; fl indicates decrease.

provided insight into the potential stabilizing effects that FKBs may offer the ACL-deficient population, and the potential stabilizing/injury protection they may offer to non-injured individuals. Given the limited amount of research involving braced non-injured subjects, it appears that familiarization/accommodation may be required before performance equals that of nonbraced non-injured subjects.

3. Conclusions and Recommendations An extensive review of the literature on ACL injury yielded more than 2000 papers published over the last decade.[109] Much of the research has ª 2009 Adis Data Information BV. All rights reserved.

concentrated on injury mechanisms as identified by Bahr and Krosshaug,[231] McIntosh[232] and Meeuwisse,[233] and thus far, although promising, no conclusive information or preventative strategies have been identified to decrease the rate and/ or severity of ACL injury; several authors have suggested that further research is necessary.[30,32] Also, no research has been conducted on the high percentage of basketball non-contact ACL injuries experienced by males,[148] and there should be concern regarding the high number of contact ACL injuries associated with soccer (for both men and women),[18,19] ice hockey[4] and football.[13] The recent AAOS[153] position paper and several studies have illustrated that knee braces generally provide 20–30% greater knee ligament Sports Med 2009; 39 (11)


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Table VI. Summary of functional knee brace (FKB) studies on non-injured subjects performing game-related activities mid-1990s to present Author(s)

FKB type

Evaluation

Findings

Stephens[229] (1995)

DonJoy GoldPoint and Omni OS-five knee braces

25 non-injured basketball players completed 2 days of running trials

No significant difference in straight line or successive turning running times between non-braced and braced testing conditions

Greene et al.[154] (2000)

Air Armor, Knee and Thigh Protection System, Berg Tradition, DonJoy Legend, McDavid Knee Guard, OMNI-ASK 101 W

30 Phoenix Junior College football players with no history of knee injury

Performance statistically not hindered while using two of six knee braces in the 40-yard dash and five of six braces during agility test. All braces had M/L and D/P had migration concerns, with only some data being statistically significant

Rishiraj et al.[215] (2000)

Generation II Poli-Axial brace

30 university athletes with no known history of knee injury. Knee joint laxity quantified using KT-1000. Performed five functional tests

Day 1 of testing: braced subjects had statistically inferior performance levels in three of five tests, enhanced performance in horizontal hop-test, and no significant difference in running down the stairs test. After brace accommodation, no significant difference between the two testing conditions in all tests

D/P = distal/proximal; M/L = medial/lateral.

protection.[9,52,82,156,157,168] In light of information presented in this paper, the application of an FKB may help to disperse GRF and/or forces from direct impact and/or to stabilize the knee joint complex. If a brace is able to offer ‘protection’, then we may not only see a reduction in knee injury severity, but possibly also a decrease in the rate of knee injuries. All injury prevention mechanisms that protect knee joint ligaments need to be investigated.[231] In particular, FKBs worn during sport competition warrant further study. Compliance, however, is an issue among non-injured athletes; when braces are worn during competitive activity, they have been shown to be related to fear of performance hindrance.[52,153-157] The results of brace accommodation are encouraging,[154,215,229] but further research is needed before performance hindrance fears are alleviated. Once this is addressed, only then can the efficacy of FKBs in preventing knee injuries during athletic performance be evaluated. Acknowledgements No funding was received for this review. The authors have no potential conflicts of interest directly relevant to the content of this review. The authors would like to thank K. (Janey) Hoover for helping with the earlier versions of this manuscript.


References 1. de Loe¨s M, Dahlstedt LJ, Thomee R. A 7-year study on risk and costs of knee injuries in male and female youth participants in 12 sports. Scand J Med Sci Sports 2000 Apr; 10: 90-7 2. Oates KM, Van Eenenaam PD, Briggs KK, et al. Comparative injury rates of uninjured anterior cruciate ligament-deficient and reconstructed knee in a skiing population. Am J Sports Med 1999; 27: 606-10 3. Delfico WE, Garrett WEJ. Mechanisms of injury of the anterior cruciate ligament in soccer players. Clin Sports Med 1998; 17: 779-85 4. Agel J, Dompier TP, Dick R, et al. Descriptive epidemiology of collegiate men’s ice hockey injuries: National Collegiate Athletic Association Injury Surveillance System, 1988-1989 through 2003-2004. J Athl Train 2007; 42: 241-8 5. Houck J. Muscle activation patterns of selected lower extremity muscles during stepping and cutting tasks. J Electromyogra Kinesiol 2003; 13: 545-54 6. Boden BP, Dean GS, Feagin JA, et al. Mechanisms of anterior cruciate ligament injury. Orthopedics 2000 Jun; 23: 573-8 7. Huston LJ, Greenfield ML, Wojtys EM. Anterior cruciate ligament injuries in the female athlete: potential risk factors. Clin Orthop Relat Res 2000 Mar; 372: 50-63 8. McNair P, Marshall R, Matheson J. Important features associated with acute anterior cruciate ligament injury. NZ Med J 1993; 103: 537-9 9. Jackson RW, Reed SC, Dunbar F. An evaluation of knee injuries in professional football team-risk factors, types of injuries, and the value of prophylactic knee bracing. Clin Sports Med 1991; 1: 1-7 10. Olson OC. The Spokane study: high school football injuries. Sports Med 1989; 8: 260-72

Sports Med 2009; 39 (11)

954

11. Thompson N. High school football injuries: evaluation. Am J Sports Med 1987; 15: 117-24 12. Ramierz M, Schaffer KB, Shen H, et al. Injuries to high school football athletes in California. Am J Sports Med 2006; 34: 1147-58 13. Dick R, Ferrara MS, Agel J, et al. Descriptive epidemiology of collegiate men’s football injuries: National Collegiate Athletic Association Injury Surveillance System, 1988-1989 through 2003-2004. J Athl Train 2007 Apr-Jun; 42: 221-33 14. Pelletier RL, Montelpare WJ, Stark RM. Intercollegiate ice hockey injuries: a case for uniform definitions and reports. Am J Sports Med 1993; 21: 78-82 15. Tegner Y, Lorentzon R. Ice hockey injuries: incidents, nature, and causes. Br J Sports Med 1991; 25: 87-9 16. Pforringer W, Smasal V. Aspects of traumatology in ice hockey. J Sports Sci 1987; 5: 327-36 17. Rishiraj N, Lloyd-Smith R, Lorenz T, et al. University men’s ice hockey: rates and risk of injuries over 6-years. J Sports Med Phys Fitness 2009; 49 (2): 159-66 18. Agel J, Evans TA, Dick R, et al. Descriptive epidemiology of collegiate men’s soccer injuries: National Collegiate Athletic Association Injury Surveillance System, 19881989 through 2002-2003. J Athl Train 2007 Apr-Jun; 42: 270-7 19. Dick R, Putukian M, Agel J, et al. Descriptive epidemiology of collegiate women’s soccer injuries: National Collegiate Athletic Association Injury Surveillance System, 1988-1989 through 2002-2003. J Athl Train 2007 Apr-Jun; 42: 278-85 20. Brooks JHH, Fuller CW, Kemp SPT, et al. Epidemiology of injuries in English professional rugby union. Part 1: match injuries. Br J Sports Med 2005 Oct; 39: 757-66 21. Giza E, Mithofer K, Farrel L, et al. Injuries in women’s professional soccer. Br J Sports Med 2005; 4: 212-6 22. So¨derman K, Adolphson J, Lorentson R, et al. Injuries in adolescent female players in European football: a prospective study over one outdoor soccer season. Scand J Med Sci Sports 2001 Oct; 11: 299-304 23. Engstro¨m B, Johansson C, Tornquist H. Soccer injuries among female elite players. Am J Sports Med 1991 JulAug; 19: 372-5 24. Orchard J, Chivers I, Aldous D. Seasonal and geographical analysis of ACL injuries risk in Australia. Sport Health 2006; 23: 20-7 25. Accident Compensation Corporation. ACC injury statistics 2006 [online]. Available from URL: http://www.acc. co.nz/about-acc/acc-injury-statistics-2006/index.htm?ref=9 [Accessed 2007 May] 26. Hewett TE, Myer GD, Ford KR. Anterior cruciate ligament injuries. Part I: mechanisms and risk factors. Am J Sports Med 2006; 34: 299-311 27. Hewett TE, Lindenfield TN, Riccobene JV, et al. The effect of neuromuscular training on the incidence of knee injury in female athletes: a prospective study. Am J Sports Med 1999; 27: 699-706 28. Yu B, Garrett WE. Mechanisms of non-contact ACL injuries. Br J Sports Med 2007 Aug; 41: i47-51


Rishiraj et al.

29. Griffin LY, Agel J, Albohm MJ, et al. Noncontact anterior cruciate ligament injuries: risk factors and prevention strategies. J Am Acad Orthop Surg 2000; 8: 141-50 30. Hewett TE, Ford KR, Myer GD. Anterior cruciate ligament injuries in female athletes. Part 2: a meta-analysis of neuromuscular interventions aimed at injury prevention. Am J Sports Med 2006; 34: 490-8 31. Kao JT, Giangarra CE, Singer G, et al. A comparison of outpatient and inpatient anterior cruciate ligament reconstruction surgery. Arthroscopy 1995 Apr; 11: 151-6 32. Griffin LY, Albohm MJ, Arendt EA, et al. Understanding and preventing noncontact anterior cruciate ligament injuries. Am J Sports Med 2006 Sep; 34: 1512-32 33. National Centre for Chronic Disease Prevention and Health Promotion. Arthritis, national statistics. Epidemiology briefs: osteoarthritis [online]. Available from URL: http:// www.cdc.gov/arthritis/arthritis/osteoarthritis.htm#7 [Accessed 2009 Sep 22] 34. Mehrotra C, Remington PL, Naimi TS, et al. Trends in total knee replacement surgeries and implications for public health, 1990–2000. Public Health Rep 2005; 120: 278-82 35. Lethbridge-Cejku M, Helmick CG, Popovic JR. Hospitalizations for arthritis and other rheumatic conditions: data from the 1976 National Hospital Discharge Survey. Med Care 2003; 41: 136-73 36. Roos EM. Joint injury causes knee osteoarthritis in young adults. Curr Opin Rheumatol 2005; 17: 195-200 37. Von Porat A, Roos EM, Roos H. High prevalence for osteoarthritis 14 years after an anterior cruciate ligament tear in male soccer players: a study of radiographic and patient relevant outcomes. Br J Sports Med 2004; 63: 269-73 38. Ford KR, Myer GD, Toms HE, et al. Gender differences in kinematics of unanticipated cutting in young athletes. Med Sci Sports Exerc 2005; 37: 124-9 39. Freedman KB, Glasgow MT, Glasgow SG, et al. Anterior cruciate ligament injuries and reconstruction among university students. Clin Orthop Relat Res 1998; 356: 208-12 40. Deacon A, Bennell K, Kiss ZS, et al. Osteoarthritis of the knee in retired, elite Australian rules footballers. Med J Aust 1997 Feb; 166: 187-90 41. Garrick JG, Requa RK. Anterior cruciate ligament injuries in men and women: how common are they? In: Griffin LY, editor. Prevention of Noncontact ACL Injuries. Rosemont (IL): American Academy of Orthopaedic Surgeons, 2001: 1-10 42. Gottlob CA, Baker CL, Pellisier JM, et al. Cost effectiveness of anterior cruciate ligament reconstruction in young athletes. Clin Orthop Relat Res 1999; 37: 272-82 43. Feagin JA, Lambert KL, Cunningham RR. Consideration of the anterior cruciate ligament in skiing. Clin Orthop Relat Res 1987; 216: 13-6 44. Carey JL, Huffman GR, Parekh SG, et al. Outcomes of anterior cruciate ligament injuries to running backs and wide receivers in the National Football League. Am J Sports Med 2006 Dec; 34: 1911-7 45. Jones HP, Appleyard RC. Meniscal and chondral loss in the anterior cruciate ligament injured knee. Sports Med 2003; 33: 1075-89

Sports Med 2009; 39 (11)


46. Roos HP, Ornell M, Gardsell P, et al. Soccer after anterior cruciate ligament injury: an incomparable combination? A national survey of incidence and risk factors and 7 year follow-up of 310 players. Acta Orthopaedica Scandinavica 1995; 66: 107-12 47. Myklebust G, Bahr R. Return to play guidelines after anterior cruciate ligament surgery. Br J Sports Med 2005 Mar; 39: 127-31 48. Kujala UM, Kettunen J, Paananen H. Knee osteoarthritis in former runners, soccer players, weight lifters, and shooters. Arthritis Rheum 1995; 38: 539-46 49. Holzach P, Bruesch M, Matter P. Epidemiology of internal knee injuries in Alpine skiing (Epidemiologie von Kniebinnenverletzungen bei alpinen Skisport). Helv Chir Acta 1994 Apr; 60: 531-7 50. Wadley GH, Albright JP. Women’s intercollegiate gymnastics: injury patterns and ‘‘permanent’’ medical disability. Am J Sports Med 1993; 2: 314-20 51. Kannus P, Renstrom P. Treatment of acute tears of the lateral ligaments of the ankle: operation, cast, or early controlled mobilization. J Bone Joint Surg Am 1991 Feb; 73: 305-12 52. Albright JP, Powell JW, Smith W, et al. Medial collateral ligament knee sprains in college football: brace wear preference and injury risk. Am J Sports Med 1994 Jan-Feb; 22: 2-11 53. National Collegiate Athletic Association. NCAA injury surveillance system summary. Indianapolis (IN): National Collegiate Athletic Association, 2002 54. National Federation of State High School Associations. High school participation survey summary. Indianapolis (IN): National Federation of State High School Associations, 2002 55. Ferrari JD, Bach BRJ, Bush-Joesph CA, et al. Anterior cruciate ligament reconstruction in men and women: an outcome analysis comparing gender. Arthroscopy 2001 Jul; 17: 588-96 56. Bagger J, Raven J, Lavard P, et al. Effect of functional knee bracing, quadriceps and hamstrings on the anterior translation in anterior cruciate ligament insufficiency: a preliminary study. J Rehabil Res Dev 1992 Winter; 29: 9-12 57. More RC, Karras BT, Neiman R, et al. Hamstrings–an anterior cruciate ligament protagonist: an in vitro study. Am J Sports Med 1993; 21: 231-7 58. Li G, Rudy TW, Sakane M, et al. The importance of quadriceps and hamstring muscle loading on knee kinematics and in-situ forces in the ACL. J Biomech 1999 Apr; 32: 395-400 59. Graves JE, Pollock ML, Leggett SH, et al. Effect of reduced training frequency on muscular strength. Int J Sports Med 1988 Oct; 9: 31-9 60. Fagenbaum MS, Darling WG. Jumping landing strategies in male and female college athletes and the implications of such strategies for anterior cruciate ligament injury. Am J Sports Med 2003 Mar-Apr; 31: 233-40 61. Lephart SM, Abt JP, Ferris CM. Neuromuscular contributions of anterior cruciate ligament injuries in females. Curr Opin Rheumatol 2002 Mar; 14: 168-73


955

62. Cowling EJ, Steele JR. Is lower limb muscle synchrony during landing affected by landing? J Electromyogr Kinesiol 2001 Aug; 11: 263-8 63. Simonsen B, Magnusson SP, Bencke J, et al. Can the hamstrings muscles protect the anterior cruciate ligament during a side-cutting maneuver? Scand J Med Sci Sports 2000; 10: 78-84 64. Pope MH, Johnson DW, Brown DW, et al. The role of the muscular in injuries to the medial collateral ligaments. J Bone Joint Surg Am 1979 Apr; 61: 398-492 65. Yu B, Garrett WE. Hamstring co-contraction does not necessarily reduce ACL loading. The XXth Congress of the International Society of Biomechanics and 29th Annual Meeting of the American Society of Biomechanics; 2005 Aug 1-5; Cleveland (OH) 66. Wojtys EM, Huston LJ, Taylor PD, et al. Neuromuscular adaptations in isokinetic, isotonic, and agility training programs. Am J Sports Med 1996 Mar-Apr; 24: 187-92 67. Aune AK, Cawley PW, Elkeland A. Quadriceps muscle contraction protects the anterior cruciate ligament during anterior tibial translation. Am J Sports Med 1997 Mar-Apr; 25: 187-9 68. Orchard J, Seward H, McGivern J. Rainfall, evaporation and the risk of non-contact anterior cruciate ligament injuries in the Australian Football League. Med J Aust 1999; 170: 304-6 69. Shultz SJ, Kirk SE, Johnson ML, et al. Relationship between sex hormones and anterior knee laxity across the menstrual cycle. Med Sci Sports Exerc 2004 Jul; 36: 1165-74 70. Pollard CD, Sigward SM, Ota S, et al. The influence of in-season injury prevention training on lower-extremity kinematics during landing in female soccer players. Clin J Sports Med 2006 May; 16: 223-37 71. Brown CN, Yu B, Kirkendall DT. Effects of increased body mass index on lower extremity motion patterns in a stop-jump task: National Athletic Trainers Association annual meeting. J Athl Train 2005; 404: 5 72. Dugan SA. Sports-related knee injuries in female athletes. Am J Phys Med Rehabil 2005 Feb; 84: 122-30 73. Myer GD, Ford KR, Hewett TE. The effects of gender on quadriceps muscle activation strategies during a maneuver that mimics a high ACL injury risk position. J Electromyogra Kinesiol 2005; 15: 181-9 74. Myer GD, Ford KR, Palumbo JP, et al. Neuromuscular training improves performance and lower extremity biomechanics in female athletes. J Strength Cond Res 2005 Feb; 19: 51-60 75. Andersen TE, Tenga A, Engebresten L, et al. Video analysis of injuries and incidents in Norwegian professional football. Br J Sports Med 2004 Oct; 38: 626-31 76. Pollard CD, Davis IM, Hamill J. Influence of gender on hip and knee mechanics during a randomly cued cutting maneuver. Clin Biomech 2004; 10: 1022-31 77. Shultz SJ, Gansneder BG, Snader TC, et al. Absolute hormone levels predict the magnitude of change in knee laxity across the menstrual cycle. J Orthop Res 2006 Feb; 24: 124-31

Sports Med 2009; 39 (11)

956

78. Besier TF, Lloyd DG, Ackland TR. Muscle activation strategies at the knee during running and cutting maneuvers. Med Sci Sports Exerc 2003 Jan; 35: 119-27 79. Myklebust G, Engebresten L, Braekken IH, et al. Prevention of anterior cruciate ligament injuries in female team handball players: a prospective intervention study over three seasons. Clin Sports Med 2003 Mar; 13: 71-8 80. Myklebust G, Holm I, Maehlum S, et al. Clinical, functional, and radiologic outcomes in team handball players 6-11 years after anterior cruciate ligament injury: a followup study. Am J Sports Med 2003 Dec; 31: 981-9 81. Uhorchak JM, Scoville CR, Williams GN, et al. Risk factors associated with noncontact injury of the anterior cruciate ligament; a prospective four-year evaluation of 859 West point cadets. Am J Sports Med 2003; 31: 831-42 82. Wojtys EM, Huston LJ, Schock HJ, et al. Gender differences in muscular protection on the knee in torsion in sizematched athletes. J Bone Joint Surg Am 2003 May; 85: 782-9 83. Lephart SM, Ferris CM, Reimann BL, et al. Gender differences in strength and lower extremity kinematics during landing. Clin Orthop Relat Res 2002 Aug; 401: 162-9 84. Matava MJ, Freehill AK, Grutzner S, et al. Limb dominance as a potential etiologic factor in noncontact anterior cruciate ligament tears. J Knee Surg 2002 Winter; 15: 11-16 85. Orchard J. Is there a relationship between ground and climate conditions and injuries in football? Sports Med 2002; 32: 419-32 86. Wu W, Hackett T, Richmond J. Effects of meniscal and articular surface status on knee stability, function, and symptoms after anterior cruciate ligament reconstruction: a long-term prospective study. Am J Sports Med 2002 Nov; 30: 845-50 87. Andrish JT. Anterior cruciate ligament injuries in the skeletally immature patient. Am J Orthop 2001 Feb; 30: 103-10 88. Beynnon BD, Slauterbeck J, Pauda D. Update on ACL risk factors and prevention strategies in the female athlete. National Athletic Trainers’ Association 52nd Annual Meeting and Clinical Symposia. Los Angeles (CA): Human Kinetics, 2001: 15-8 89. Teitz CC. Video analysis of ACL injuries. In: Griffin LY, editor. Prevention of noncontact ACL injuries. Rosemont (IL): American Academy of Orthopaedic Surgeons, 2001: 93-6 90. Colby S, Francisco A, Yu B, et al. Electromyographic and kinematic analysis of cutting maneuvers: implications for anterior cruciate ligament injuries. Am J Sports Med 2000 Mar-Apr; 28: 234-40 91. Heiderscheit BC, Hamill J, Caldwell GE. Influence of Q-angle on lower-extremity running kinematics. J Orthop Sports Phys Ther 2000; 30: 271-8 92. Karageanes SJ, Blackburn K, Vangelos ZA. The association of the menstrual cycle with the laxity of the anterior cruciate ligament in adolescents female athletes. Clin J Sports Med 2000; 10: 162-8 93. Heitz NA. Hormonal changes throughout the menstrual cycle and increased anterior cruciate ligament laxity in females. J Athl Train 1999; 1999: 144-9


Rishiraj et al.

94. MacWilliams BA, Wilson DR, DesJardins JD, et al. Hamstrings cocontraction reduces internal rotation, anterior translation, and anterior cruciate ligament load in weight bearing flexion. J Orthop Res 1999; 17: 817-22 95. Slauterbeck J, Clevenger C, Lundberg W, et al. Estrogen level alters the failure load of the rabbit anterior cruciate ligament. J Orthop Res 1999; 17: 405-8 96. Branch TP, Hunter RF, Reynolds P. Controlling anterior tibial displacement under static load: a comparison of two braces. Orthopedics 1988 Sep; 11: 1249-52 97. Shelbourne K, Throp TJ, Klootwyk TE. The relationship between intercondylar notch width of the femur and the incidence of anterior cruciate ligament tears: a prospective study. Am J Sports Med 1998; 26: 402-8 98. Steele JR. Knee function of chronic ACL deficient patients during static knee laxity assessment and dynamic deceleration. Wollongong (NSW): University of Wollongong, 1997 99. Teitz CC, Lind BC, Sacks BM. Symmetry of the femoral notch width index. Am J Sports Med 1997; 25: 687-90 100. Abubaker AO, Hebda PC, Gunsolley JN. Effects of sex hormones on protein and collagen content of the temporomandibular joint disc of the rat. J Oral Maxillofac Surg 1996 Jun; 54: 721-8 101. Hewett TE, Stroupe AL, Nance TA, et al. Plyometric training in female athletes: decreased impact forces and increased hamstring torques. Am J Sports Med 1996; 24: 765-73 102. Lambson RB, Barnhill BS, Higgins RW. Football cleat designed and its effect on anterior cruciate ligament injuries: a three-year analysis prospective study. Am J Sports Med 1996; 24: 155-9 103. Sarwar R, Beltran NB, Rutherford OM. Changes in muscle strength, relaxation rate and fatigability during the human menstrual cycle. J Physiol 1996; 493: 267-72 104. Wojtys EM, Wylie BB, Huston LJ. The effects of muscle fatigue on neuromuscular function and anterior tibial translation in healthy knees. Am J Sports Med 1996 SepOct; 24: 615-21 105. Beynnon BD, Fleming BC, Johnson RJ, et al. Anterior cruciate ligament strain behavior during rehabilitation exercises in vivo. Am J Sports Med 1995 Feb; 23: 24-34 106. Du¨rselen L, Claes L, Keifer H. The influence of muscle force and external loads on cruciate ligament strain. Am J Sports Med 1995 Jan-Feb; 23: 129-36 107. Kim AW, Rosen AM, Brander VA, et al. Selective muscle activation following electrical stimulation of the collateral ligaments of the human knee joint. Arch Phys Med Rehabil 1995 Aug; 76: 750-7 108. Markolf KL, Bargar SC, Shoemaker SC, et al. The role of joint load in knee stability. J Bone Joint Surg Am 1981 Apr; 63: 570-85 109. Miller RH. Knee injuries. In: Canale ST, editor. Campbell’s operative orthopaedics. 10th ed. Philadelphia (PA): Mosby; 2003: 2155-338 110. Mandelbaum BR, Silvers HJ, Watanabe DS. Effectiveness of a neuromuscular and proprioceptive training program in preventing anterior cruciate ligament injuries in female

Sports Med 2009; 39 (11)


111.

112.

113.

114.

115.

116.

117.

118.

119.

120.

121.

122.

123.

124.

athletes: a two year follow-up. Am J Sports Med 2005; 33: 1003-10 Olsen OE, Myklebust G, Engebresten L, et al. Exercises to prevent lower limb injuries in youth sports: cluster randomised controlled trials. BMJ 2005; 330: 449 Gilchrist JR, Mandelbaum BR, Melancon H. A randomised controlled trial to prevent anterior cruciate ligament injuries in female collegiate soccer players [abstract no. 6-7]. American Orthopaedic Society of Sports Medicine Speciality Day; 2004 Mar 13; San Francisco (CA) Pfeiffer RP, Shea KG, Grandstand S. Effects of a knee ligament injury prevention (KLIP) program on the incidence of noncontact ACL injury: a two-year prospective study of exercise intervention in high school female athletes [podium presentation]. American Orthopaedic Society of Sports medicine Speciality Day; 2004 Mar 13; San Francisco (CA) Wedderkopp N, Kaltoft M, Hiolm R, et al. Compassion of two intervention programmes in young female players in European handball: with and without ankle discs. Scand J Med Sci Sports 2003; 13: 371-5 Heidt RS, Sweeterman LM, Carlonas RL, et al. Avoidance of soccer injuries with preseason conditioning. Am J Sports Med 2000; 28: 659-62 So¨derman K, Werner S, Pietila¨ T, et al. Balance board training: prevention of traumatic randomised intervention study. Knee Surg Sports Traunatol Arthrosc 2000; 8: 356-63 Chappell JD, Limpisvasti O. Effect of a neuromuscular training program on the kinetics and kinematics of jumping tasks. Am J Sports Med 2008 Jun; 36: 1081-6 Petersen W, Braun C, Bock W, et al. A controlled prospective case control study of a prevention training program in female team handball players: the German experience. Arch Orthop Trauma Surg 2005 Nov; 125: 614-21 Caraffa A, Cerulli G, Projetti A, et al. Prevention of anterior cruciate ligament injuries in soccer: a prospective controlled study of proprioceptive training. Knee Surg Sports Traunatol Arthrosc 1996; 4: 19-21 Ettlinger CF, Johnson RJ, Shealy JE. A method to help reduce the risk of serious knee sprains incurred in alpine skiing. Am J Sports Med 1995 Sep-Oct; 23: 531-7 Griffis ND, Nequist SW, Yearout K. Injury prevention of the anterior cruciate ligament [abstract]. American Orthopaedic Society of Sports Medicine: meeting abstracts, and instructional courses. Traverse City (MI): American Orthopaedic Society of Sports Medicine, 1989 Engebretsen AH, Myklebust G, Holme I, et al. Prevention of injuries among male soccer players: a prospective, randomized intervention study targeting players with previous injuries or reduced function. Am J Sports Med 2008 Jun; 36: 1052-60 McGuinn PA, Mattacola CG, Malone TR, et al. Strength training for 6-weeks does not significantly alter landing mechanisms of female collegiate basketball athletes. J Orthop Sports Phys Ther 2007 Feb; 37: A24 Herman DC, Weinhold PS, Guskiewicz KM, et al. The effects of strength training on the lower extremity biomechanics of female recreational athletes during a stopjump task. Am J Sports Med 2008 Apr; 36: 733-40


957

125. Herman DC, Weinhold PS, Guskiewicz KM, et al. The effects of strength training on the neuromuscular characteristics of a stop-jump in females recreational athletes [abstract]. J Orthop Sports Phys Ther 2007 Feb; 37: A24 126. Cronin JB, Bressel E, Fkinn L. Augmented feedback reduces ground reaction forces in the landing phase of the volleyball spike jump. J Sports Rehabil 2008 May; 17: 148-59 127. Gilchrist J, Mandelbaum BR, Melancon H, et al. A randomized controlled trial to prevent noncontact anterior cruciate ligament injury in female collegiate soccer players. Am J Sports Med 2008 Aug; 36: 1476-83 128. Myer GD, Chu DA, Brent JL, et al. Trunk and hip control neuromuscular training for the prevention of knee joint injury. Clin Sports Med 2008 Jul; 27: 425-48 129. Pańics G, Ta´llay A, Pavlik A, et al. Effect of proprioception training on knee joint position sense in female team handball players. Br J Sport Med 2008; 42: 472-6 130. Zebis MK, Bencke J, Andersen LL, et al. The effects of neuromuscular training on knee joint motor control during sidecutting in female elite soccer and handball players. Clin J Sports Med 2008 Jul; 18: 329-37 131. Myklebust G, Engebretsen L, Braekken IH, et al. Prevention of noncontact anterior cruciate ligament injuries in elite and adolescent female team handball athletes. Instr Course Lect 2007; 56: 407-18 132. Myer GD, Ford KR, Brent JL, et al. Differential neuromuscular training effects on ACL injury risk factors in ‘‘high-risk’’ versus ‘‘low-risk’’ athletes. BMC Musculoskelet Disord 2007 May; 8: 39-46 133. Trowbridge CA, Richard MD, Knight KL, et al. The effects of strength training and plyometric training on joint position and joint moments of the female knee [abstract]. J Orthop Sports Phys Ther 2007 Feb; 37: A25 134. Hurd WJ, Chemielewski TL, Snyder-Mackler L. Perturbation-enhanced neuromuscular training alters muscle activity in female athletes. Knee Surg Sports Traunatol Arthrosc 2006 Jan; 14: 60-9 135. Myer GD, Ford KR, McLean SG, et al. The effects of plyometric versus dynamic stabilization and balance training on lower extremity biomechanics. Am J Sports Med 2006 Mar; 34: 445-55 136. Lephart SM, Abt JP, Ferris CM, et al. Neuromuscular and biomechanical characteristic changes in high school athletes: a plyometric versus basic resistance program. Br J Sport Med 2005 Dec; 39: 932-8 137. Irmischer BS, Harris C, Pfeiffer RP, et al. Effects of a knee ligament injury prevention exercise program on impact forces in women. J Strength Cond Res 2004 Nov; 18: 703-7 138. Paterno MV, Myer GD, Ford KR, et al. Neuromuscular training improves single-limb stability in young female athletes. J Orthop Sports Phys Ther 2004 Jun; 34: 305-16 139. Cahill BR, Griffith EH. Effect of preseason conditioning on the incidence and severity of high school football knee injuries. Am J Sports Med 1978 Jul-Aug; 6: 180-4 140. Mizner RL, Kawaguchi JK, Chmielewshi TL. Muscle strength in the lower extremity does not predict postinstruction improvements in the landing patterns of female athletes. Orthop Sports Phys Ther 2008 Jun; 38: 353-61

Sports Med 2009; 39 (11)

958

141. Pfeiffer RP, Shea KG, Roberts D, et al. Lack of effect of a knee ligament injury prevention program on the incidence of noncontact anterior cruciate ligament injury. J Bone Joint Surg Am 2006 Aug; 88: 1769-74 142. Chappell JD, Herman DC, Knight BS, et al. Effect of fatigue on knee kinetics and kinematics in stop-jump tasks. Am J Sports Med 2005 Jul; 33: 1022-9 143. Knobloch K, Martin-Schmitt S, Go¨sling T, et al. Prospective proprioceptive and coordinative training for injury reduction in elite female soccer [in German]. Sportverletz Sportschaden 2005 Sep; 19: 123-9 144. Holm I, Fosdahl MA, Friis A, et al. Effect of neuromuscular training on proprioception, balance, muscle strength, and lower limb function in female team handball players. Clin J Sports Med 2004 Mar; 14: 88-94 145. Wilkerson GB, Colston MA, Short NI, et al. Neuromuscular changes in female collegiate athletes resulting from a plyometric jump-training program. J Athl Train 2004 Mar; 39: 17-23 146. Wedderkopp N, Kaltoft M, Lundgaard B, et al. Prevention of injuries in young female players in European team handball: a prospective intervention study. Scand J Med Sci Sports 1999 Feb; 9: 41-7 147. Chappell JD, Creighton RA, Giuliani C, et al. Kinematics and electromyography of landing preparation in vertical stop-jump: risks for noncontact anterior cruciate ligament injury. Am J Sports Med 2007; 35 (2): 235-41 148. Dick R, Hertel J, Agel J, et al. Descriptive epidemiology of collegiate men’s basketball injuries: National Collegiate Athletic Association Injury Surveillance System, 19881989 through 2003-2004. J Athl Train 2007; 42: 194-201 149. Agel J, Olson DE, Dick R, et al. Descriptive epidemiology of collegiate women’s basketball injuries: National Collegiate Athletic Association Injury Surveillance System, 1988-1989 through 2003-2004. J Athl Train 2007 Apr-Jun; 42: 202-10 150. Nicholas JA. The five-one reconstruction of anteromedial instability of the knee: indications, technique, and the results in fifty-two patients. J Bone Joint Surg Am 1973 Jul; 55: 899-922 151. American Association of Orthopaedics Surgeons. Position paper: the use of knee braces. Rosemont (IL): American Association of Orthopaedics Surgeons, 1987 152. Wirth MA, DeLee JC. The history and classification of knee braces. Clin Sports Med 1990; 9: 731-41 153. American Association of Orthopaedics Surgeons. Position paper: the use of knee braces. Rosemont (IL): American Association of Orthopaedics Surgeons, 2004 154. Greene DL, Hamson KR, Bay RC, et al. Effects of protective knee bracing on speed and agility. Am J Sports Med 2000; 28: 453-9 155. Paluska SA, McKeag DB. Knee braces: current evidence and clinical recommendations for their use. Am Fam Physician 2000 Jan; 61: 411-8, 23-24 156. Najibi S, Albright JP. The use of knee braces. Part I: prophylactic knee braces in contact sports. Am J Sports Med 2005; 33: 602-11


Rishiraj et al.

157. Albright JP, Powell JW, Smith W, et al. Medial collateral ligament knee sprains in college football: effectiveness of preventive braces. Am J Sports Med 1994 Jan-Feb; 22: 12-8 158. Garrick JG, Requa RK. Prophylactic knee bracing. Am J Sports Med 1987; 15: 471-6 159. Teitz CC, Hermanson BK, Kronmal RA, et al. Evaluation of the use of braces to prevent injury to the knee in collegiate football players. J Bone Joint Surg Am 1987; 69A: 2-9 160. Anderson G, Zeamen SC, Rosenfeld RT. The Anderson knee stabler. Phys Sportsmed 1979; 7: 125-7 161. Hansen BL, Ward JC, Diehl RC. The preventative use of the Anderson knee stabler in football. Phys Sportsmed 1985; 13: 75-81 162. Schriner JL. The effectiveness of knee bracing in preventing knee injuries in high school athletes [abstract]. Med Sci Sports Exerc 1985; 17: 254 163. Hewson GF, Mendini RA, Wang JB. Prophylactic knee bracing in college football. Am J Sports Med 1986; 14: 262-6 164. Rovere GD, Haupt HA, Yates CS. Prophylactic knee bracing in college football. Am J Sports Med 1987 MarApr; 15: 111-6 165. Grace TG, Skipper BJ, Newberry JC, et al. Prophylactic knee braces and injury to the lower extremity. J Bone Joint Surg Am 1988 Mar; 70: 422-7 166. Zemper ED. A two year prospective study of prophylactic knee braces in a national sample of college football players. Sports Train Med Rehab 1990; 1: 287-96 167. Taft TN, Hunter S, Funderburk CH. Preventative lateral knee bracing in football. Nashville (TN): American Orthopedic Society of Sports Medicine, 1989 168. Sitler M, Ryan J, Hopkinson W, et al. The efficacy of a prophylactic knee brace to reduce knee injuries in football: a prospective randomised study at West Point. Am J Sports Med 1990 May-Jun; 18: 310-5 169. Paulos LE, Drawbert JP, France P, et al. Lateral knee braces in football: do they prevent injury? Phys Sportsmed 1976; 14: 119-24 170. France EP, Paulos LE, Jayaraman G, et al. The biomechanics of lateral knee bracing. Part II: impact response of the braced knee. Am J Sports Med 1987 Sep-Oct; 15: 430-8 171. Paulos LE, France EP, Rosenberg TD, et al. The biomechanics of lateral knee bracing. Part I: response of the valgus restraints to loading. Am J Sports Med 1987 Sep-Oct; 15: 419-29 172. Hofmann AA, Wyatt RWB, Bourne MH, et al. Knee stability in orthotic knee braces. Am J Sports Med 1984 Sep-Oct; 12: 371-4 173. Baker BE, VanHanswyk E, Bogosian S, et al. A biomechanical study of the static effect of knee braces on medial stability. Am J Sports Med 1987 Nov-Dec; 15: 566-70 174. Paulos LE, France EP, Rosenberg TD, et al. The biomechanics of lateral knee bracing. Part I: response of the valgus restraints to loading. Am J Sports Med 1987 Sept-Oct; 15: 419-29

Sports Med 2009; 39 (11)


175. Bassett GS, Fleming BW. The Lenox Hill brace in anterolateral rotatory stability. Am J Sports Med 1983 SepOct; 11: 345-8 176. Colville MR, Lee CL, Ciullo JV. The Lenox Hill brace: an evaluation of effectiveness in treating knee instability. Am J Sports Med 1986 Jul-Aug; 14: 257-61 177. Rink PC, Scott RA, Lupo RL, et al. Team physician #7: a comparative study of functional bracing in the anterior cruciate deficient knee. Orthopaed Rev 1989 Jun; 18: 719-27 178. Mishra DK, Daniel DM, Stone ML. The use of functional knee braces in the control of pathologic anterior knee laxity. Clin Orthop Relat Res 1989 Apr; 241: 213-20 179. Branch TP, Hunter RF. Functional analysis of anterior cruciate braces. Clin Sports Med 1990 Oct; 9: 771-97 180. Vailas JC, Tibone JE, Perry J. Dynamic biomechanical effects of functional bracing. Med Sci Sports Exer 1989; 21 Suppl.: S82 181. Knutzen KM, Bates BJ, Hamill J. Electrogoniometery of post-surgical knee bracing in running. Am J Phys Med 1983 Aug; 62: 172-81 182. Knutzen KM, Bates BT, Schot P, et al. A biomechanical analysis of two functional knee braces. Med Sci Sports Exerc 1987 Jun; 19: 303-9 183. Czerniecki JM, Lippert F, Olerud JE. A biomechanical evaluation of tibiofemoral rotation in anterior cruciate deficient knees during walking and running. Am J Sports Med 1988 Jul-Aug; 16: 327-31 184. Tibone JE, Antich TJ, Fanton GS, et al. Functional analysis of anterior cruciate ligament instability. Am J Sports Med 1986 Jul-Aug; 14: 276-84 185. Kinematics of anterior cruciate deficient legs during sidestep cutting with and without a derotational knee brace [presented in Branch and Hunter[179]]. Gainesville (FL): University of Florida, 1990 186. DeVita P, Hunter PB, Skelly WA. Effects of a functional knee brace on the biomechanics of running. Med Sci Sports Exerc 1992 Jul; 24: 797-804 187. Vailas JC, Pink M. Biomechanical effects of functional bracing: practical implications. Sports Med 1993 Mar; 15: 210-8 188. Arnheim DD. Modern principles of athletic training. 6th ed. St. Louis (MO): Times Mirror/Mosby College Publishing, 1984 189. Cook FF, Tibone JE, Redfern FC. A dynamic analysis of a functional brace for anterior cruciate ligament insufficiency. Am J Sports Med 1989 Jul-Aug; 17: 519-24 190. Corcoran PJ, Jebsen RH, Brengelmann GL, et al. Effects of plastic and metal leg braces on speed and energy cost of hemiparetic ambulation. Arch Phys Med Rehabil 1970 Feb; 51: 69-77 191. Reed SC. An evaluation of the C.A.R.S: UBC orthosis. Orthopedics 1979; 33: 25-38 192. Soule RG, Goldman RF. Energy cost of loads carried on the head, hands, and feet. J Appl Physiol 1969; 27: 687-90 193. Houston ME, Goenans PH. Leg muscle performance of athletes with and without knee support braces. Arch Phys Med Rehabil 1982 Sep; 63: 431-2


959

194. Iglehart TK. Strength and motor task performance as effected by the carbon titanium knee brace in normal healthy males. Fort Collins (CO): Colorado State University Department of Physical Education, 1985: 1-12 195. Tegner Y, Lysholm J. Derotational brace and knee function in patients with anterior cruciate ligament tears. Arthroscopy 1985; 1: 264-7 196. Zetterlund AE, Serfass RC, Hunter RE. The effects of wearing the complete Lenox Hill Derotation Brace on energy expenditure during horizontal treadmill running at 161 metres per minute. Am J Sports Med 1986; 14: 73-6 197. Highgenboten CL, Jackson A, Meske N, et al. The effects of knee brace on perceptual and metabolic variables during horizontal treadmill running. Am J Sports Med 1991; 19: 639-43 198. Marans HJ, Jackson RW, Piccinin J, et al. Functional testing of braces for anterior cruciate ligament-deficient knees. Can J Surg 1991; 34: 167-72 199. Veldhuizen FM, Koene M, Oostvogel HJM, et al. The effects of supportive knee brace on leg performance in healthy subjects. Int J Sports Med 1991; 12: 577-80 200. Styf JR, Nakostine M, Gershuni DH. Functional knee braces increase intramuscular pressures in the anterior compartment of the leg. Am J Sports Med 1992; 20: 46-9 201. Styf JR. The effects of functional knee bracing on muscle function and performance. Sports Med 1999; 28: 77-81 202. Fonesca ST, Magee D, Wessel J. Validation of performance test for outcome evaluation of knee function. Clin J Sports Med 1992; 2: 251-6 203. Vailas JC, Tibone JE, Perry J, et al. The effects of functional knee bracing on the dynamic biomechanics of the cross-cut maneuver. J Sports Trauma Res 1990; 12: 197-206 204. Decoster LC, Vailas JC. Functional anterior cruciate ligament bracing: a survey of current brace prescriptions patterns. Orthopedics 2003 Jul; 26: 701-6 205. Decoster LC, Vailas JC, Swartz WG. Functional ACL bracing: a survey of current opinion and practice. Am J Orthop 1995 Nov; 24: 838-43 206. Cawley PW, France E, Paulos LE. The currents state of functional knee bracing research: a review of literature. Am J Sports Med 1991 May-Jun; 19: 226-33 207. Beynnon BD, Pope MH, Wertheimer CM. The effect of functional knee bracing on the anterior cruciate ligament in vivo. J Bone Joint Surg Am 1992 Oct; 74: 1298-312 208. Kramer JF, Dubowitz T, Fowler P. Thiel functional knee braces and dynamic performance: a review. Clin Sports Med 1997; 7: 32-9 209. D’Ambrosia R. Knee braces. Orthopedics 1988 Sep; 11: 1247 210. Liu SH. Current review: functional knee bracing. Clin Orthop Relat Res 1995; 317: 273-381 211. Martin TJ. Technical report: knee brace use in the young athlete. Pediatrics 2001; 108: 503-7 212. Fleming BC, Renstrom PA, Beynnon BD, et al. The influence of functional knee bracing on anterior cruciate ligament strain biomechanics in weight bearing and nonweightbearing knees. Am J Sports Med 2000 Nov-Dec; 28: 815-24

Sports Med 2009; 39 (11)

960

213. Birmingham TB, Kramer JF, Kirkley A, et al. Knee bracing after ACL reconstruction: effects on postural control and proprioception. Med Sci Sports Exerc 2001 Aug; 33: 1253-8 214. Pietrosimone BG, Grindstaff TL, Linens SW, et al. A systematic review of prophylactic braces in the prevention of knee ligament injuries in collegiate football players. J Athl Train 2008 Jul-Aug; 43: 409-15 215. Rishiraj N, Taunton JE, Clement DB, et al. Role of functional knee bracing in a dynamic setting. NZ J Sports Med 2000; 28: 54-61 216. Ramsey DK, Lamontagne M, Wretenberg PF, et al. Assessment of functional knee bracing: an in vivo threedimensional kinematic analysis of the anterior cruciate deficient knee. Clin Biomech 2001 Jan; 16: 61-70 217. Beynnon BD, Fleming BC, Labovitch R, et al. Chronic anterior cruciate ligament deficiency is associated with increased anterior translation of the tibia during the transition from non-weightbearing to weightbearing. J Orthop Res 2002 Mar; 20: 332-7 218. Beynnon BD, Fleming BC, Churchill DL, et al. The effect of anterior cruciate ligament deficiency and functional knee bracing on translation of the tibia relative to the femur during nonweightbearing and weight bearing. Am J Sports Med 2003 Jan-Feb; 31: 99-105 219. Ramsey DK, Wretenberg PF, Lamontagne M, et al. Electromyographic and biomechanic analysis of anterior cruciate ligament deficiency and functional knee bracing. Clin Biomech 2003 Jan; 18: 28-34 220. Smith J, Malanga GA, Yu B, et al. Effects of functional knee bracing on muscle firing patterns about the chronic anterior cruciate ligament-deficient knee. Arch Phys Med Rehabil 2003 Nov; 84: 1680-6 221. Risberg MA, Holm I, Steen H, et al. The effect of knee bracing after anterior cruciate ligament reconstruction. Am J Sports Med 1999 Jan-Feb; 27: 76-83 222. Wu GKH, Ng GYF, Mak AFT. Effects of knee bracing on sensorimotor function of subjects with anterior cruciate ligament reconstruction. Am J Sports Med 2001 Sep-Oct; 29: 641-5


Rishiraj et al.

223. McDevitt ER, Taylor DC, Miller MD, et al. Functional bracing after anterior cruciate ligament reconstruction. Am J Sports Med 2004; 32: 1887-92 224. McNair PJ, Stanley SN, Strauss GR. Knee bracing: effects of proprioception. Arch Phys Med Rehabil 1996 Mar; 77: 287-9 225. Kocher MS, Sterett WI, Briggs KK, et al. Effect of functional bracing on subsequent knee injury in ACLdeficient professional skiers. J Knee Surg 2003 Apr; 16: 87-92 226. Culp MT, Gushiewicz KM, Ross SE, et al. Prophylactic knee bracing and local fatigue have no effect of joint position sense of the uninjured knee in a closed kinetic chain. J Athl Train 2004 Jun; 39: S-103 227. Yu B, Herman D, Preston J, et al. Immediate effect of a knee brace with a constraint to knee extension on knee kinematics and ground reaction forces. Am J Sports Med 2004; 32: 1136-43 228. Wojtys EM, Kothari SU, Huston LJ. Anterior cruciate ligament functional brace use in sports. Am J Sports Med 1996 Jul-Aug; 24: 539-46 229. Stephens DL. The effects of functional knee braces on speed in collegiate basketball players. J Orthop Sports Phys Ther 1995; 22: 259-62 230. Flynn RK, Pedersen CL, Brimingham TB, et al. The familial predisposition towards tearing the anterior cruciate ligament: a case control study. Am J Sports Med 2005; 33: 23-38 231. Bahr R, Krosshaug T. Understanding the injury mechanisms: a key component to prevent injuries in sports. Br J Sports Med 2005 Jun; 39: 324-9 232. McIntosh AS. Risk compensation, motivation, injuries, and biomechanics in competitive sports. Br J Sports Med 2005; 39: 2-3 233. Meeuwisse WH. Assessing causation in sports injury: a multifactorial model. Clin J Sports Med 1994; 4: 166-70

Correspondence: Neetu Rishiraj, ACTIN Health & Rehabilitation Inc., 5767 Oak Street, Vancouver, BC, Canada. Email: [email protected]

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REVIEW ARTICLE


Physical Activity and Preterm Birth A Literature Review Marlos Rodrigues Domingues, Alicia Matijasevich and Aluı´sio J.D. Barros Post-Graduate Program in Epidemiology, Federal University of Pelotas, Pelotas, Brazil

Contents Abstract. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. Reviewing Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. Physical Activity Studies and Preterm Birth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Occupational Physical Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Fatigue and Job Satisfaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Leisure-Time Physical Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4 All-Domain or Other Physical Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. Limitations Found in the Reviewed Literature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5. Physiological Aspects of Physical Activities in Pregnancy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6. Physical Activity and Preterm Birth: Considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Abstract

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Preterm birth is a major reason for infant mortality and morbidity, representing a public health concern worldwide. Regular and voluntary physical activity is healthy behaviour that should be incorporated by everyone, including pregnant women. On the other hand, some women are exposed to highly demanding occupational physical activities during pregnancy that might represent a threat to the fetus and to their own health. This paper is a literature review of studies (1987–2007) on physical activity during pregnancy and its relationship to preterm birth. Although the effects measured by the studies are not strong and the evidence is impaired by many methodological flaws, it seems that recreational or leisure-time physical activities performed regularly provide protection against prematurity. Studies on occupational physical activities, especially standing for long periods, present contrasting results – some presenting standing as a risk factor, but most showing no association. Housework and other daily activities do not seem to be associated with preterm birth. Regardless of the methodological aspects of the studies reviewed, there is a chance that the real effect of occupational physical activity is being blurred by some underlying factors not easily measured in epidemiological investigations. Our conclusions do not reject the idea that working conditions might represent danger for the pregnancy outcome, but only raise the question that maybe the mechanisms through which employment-related physical activities have been considered up till now could be better and more thoroughly studied. Future studies should pay additional attention to psychological and socioeconomic characteristics, without neglecting biological plausibility.

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Gestational age is known to be one of the most important predictors of an infant’s subsequent health and survival.[1] The incidence of preterm birth (birth before 37 weeks of gestation) ranges from 5% to 7% of live births in most developed countries and up to 25% in developing nation settings.[2] There is also evidence that preterm birth rates have been rising fairly steadily in the past few years in many countries, and therefore it represents a major public health concern.[3-6] Information available on risk factors associated with preterm birth considers individual-level behavioural and psychosocial factors, environmental exposures, medical conditions, infertility treatments, biological factors and genetics.[6-9] Even though in a high percentage of preterm births the aetiology cannot be positively defined, several maternal aspects have been thought to contribute to preterm birth. Poor socioeconomic status, maternal malnutrition, illiteracy, extremes of maternal age and cigarette smoking are the main non-obstetric risk factors identified.[10-12] In addition, cervical incompetence, multiple gestations, short birth intervals, premature membrane rupture and previous preterm birth are some of the obstetric risk factors that have been associated with preterm birth.[7-9] Other medical conditions such as urinary and genital tract infections and history of adverse pregnancy outcome have also been associated with preterm delivery.[13,14] Another factor to consider is that the higher medicalization of pregnancy and childbirth may increase the chance of iatrogenic preterm deliveries.[15] Maternal psychological profile plays a role in preterm birth determination: stress, anxiety and depression are frequently associated with prematurity.[16-18] Moutquin suggests that infection is mostly responsible for extreme preterm birth, while stress and lifestyle influence mild preterm birth, and a mixture of both conditions contributes to extreme preterm birth.[19] The preterm birth rates seem to be on the rise as there are more nearterm babies (34–36 weeks).[20] These deliveries often are preceded by labour induction in women with conditions such as hypertension and diabetes mellitus.[21] ª 2009 Adis Data Information BV. All rights reserved.

Over the last decades an increasing interest in physical activity during pregnancy resulted in several studies evaluating the impact of active lifestyles and occupational physical tasks on pregnancy outcomes such as birthweight and prematurity. The aim of this paper is, based on a literature review, to explore potential relationships between physical activity and preterm birth. Special attention is devoted to the contrasting physiological aspects regarding occupational and leisuretime physical activities. 1. Reviewing Methods We conducted a search for papers published between 1987 and November 2007 in English, Portuguese or Spanish that studied preterm birth as the main or secondary outcome and considered some kind of physical activity as an exposure. The databases searched were: MEDLINE, Lilacs, MedCarib, CiteBase, Paho, Cybertesis, ProQuest Dissertation Library, Syracuse University Library, Popline and EMBASE. Main search terms (or a combination of terms) were ‘Preterm’, ‘Premature’, ‘Prematurity’, ‘Physical Activity’, ‘Exercise’, ‘Occupation’, ‘Work’, ‘Occupational’, ‘Birth’ and ‘Delivery’. References from retrieved papers were searched to identify additional references. In addition, we contacted several authors to obtain reprints and information about unpublished material. Four studies published before 1987 were also included due to their frequent citation in studies within the time range of this review. Some review papers were reference sources during our search and reviewers’ commentaries were evaluated. 2. Recommendations Currently there is no guideline concerning the most appropriate physical activity to be performed throughout gestation: only some precautions are advocated. Pregnant women and physicians must consider the same precautions taken with nonpregnant populations besides relying on common sense and bearing in mind past activities Sports Med 2009; 39 (11)

Physical Activity and Preterm Birth

performed. Women should avoid activities with potential risk of trauma, like horseback riding and contact sports.[22] Scuba diving is another activity to be avoided since there is a chance of adverse outcome because the fetus is not protected from decompression problems and is at risk of malformation and gas embolism after decompression disease.[23] When exercising lying on the ground, women must be advised to avoid the supine position, especially during the second and third trimesters. Because of the increased uterus weight, this posture might result in vena cava compression, compromising venous return and possibly decreasing cardiac output and blood pressure – a situation known as supine hypotensive syndrome.[24] 3. Physical Activity Studies and Preterm Birth We reviewed 47 papers on this subject, besides complementary literature, to help us understand the relationship between physical activity and preterm birth. Basically, three study types were available discussing physical activity and preterm birth: (i) occupational physical activity; (ii) leisure-time physical activity; and (iii) all-domain physical activity (or a mixture of several activities). We could identify 25 papers dealing exclusively with occupational exposures (table I), six limited to leisure-time physical activity (table II), and 16 studies that evaluated both occupational and leisuretime activities or all-domain physical activity assessments (table III), including housework and other daily activities. 3.1 Occupational Physical Activities

Prolonged standing is by far the most investigated occupational activity regarding preterm birth. From the 41 studies assessing occupational exposures, 27 evaluated standing postures. Five studies found that standing at work was a risk factor for preterm birth, showing results varying from odds ratio (OR) = 1.26 (95% CI 1.1, 1.5) in a multicentre case-control study by Saurel-Cubizolles et al.[47] that defined standing as >6 daily hours to OR = 4.10 (95% CI 1.29, 13.10) in ª 2009 Adis Data Information BV. All rights reserved.

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Ritsmitchai et al.,[66] a case-control study with lowschooling Thai women that considered standing when women stand for at least 3 hours per day. Small numbers in the Ritsmitchai et al. study may have hindered the adjusted analysis, for example, from the 223 cases; only 32 women were exposed to standing during pregnancy and only five women belonged to the higher schooling category. The remaining 22 studies found no significant associations between prematurity and standing at work. Lifting activities have been assessed and discussed in prematurity, fetal growth and birthweight studies.[30,58,62-65,67,71] With respect to lifting weights and prematurity specifically, Ahlborg et al.[58] found that lifting (‡12 kg) more than 50 times a week increased the chance of preterm birth only among women who stopped working before the 32nd week of gestation. The same was found by McDonald et al.,[30] who reported that lifting heavy weights more than 15 times a day was only a risk factor for women who stopped working before the 28th week of gestation. This relationship could be an example of reverse causality often left out in the discussion of several such papers. Ahlborg et al.[58] argued that perhaps cervical insufficiency could be triggered by lifting weights among susceptible women and that such women could leave work earlier because of symptoms or a previous preterm delivery experience. Leaving out these subgroup analyses, we did not find evidence that lifting heavy weights per se would provoke any kind of adaptation known to be highly related to prematurity. Berkowitz et al.,[56] Fortier et al.[65] and Koemeester et al.[64] studied both leisure-time physical activity and occupational physical activity, finding no association between occupational activities and preterm birth. Different results might be due to contrasting definitions. In terms of exposure definition, the main occupational exposure – standing – is categorized by some papers as yes/no,[36] below or above 3 hours,[66] below or above 8 hours,[30] or in three,[47] four[59] or five categories.[68] Some use weekly exposure[68,71] while most use daily measures. These disparities reinforce the difficulty in Sports Med 2009; 39 (11)

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Table I. Studies evaluating exclusively occupational physical activities (PA) and preterm birth (PB) Study design (no. of subjects)

Physical activity

Effect/conclusions (OR; 95% CI)

Limitations

Mamelle et al.[25] (1984)

Retro (1928)

Fatigue scorea

Physical exertion increases the risk of prematurity (1.7; 1.1, 2.0). Mental stress was associated with PB (1.8; 1.1, 2.2)

Saurel-Cubizolles et al.[26] (1985)

Retro (621)

Standing, carrying heavy loads and heavy cleaning tasks

Zuckerman et al.[27] (1986)

Retro (1507)

Standing

Higher PB rate among cleaners, cooks, etc. and in the presence of at least two of the arduous conditions: standing, carrying heavy loads and heavy cleaning No association

Fatigue score is not specific for PA, as it considers mental stress and many different aspects of the environment such as cold, noise, gases, chemical manipulation and wet atmosphere Poor statistics

Saurel-Cubizolles and Kaminski[28] (1987)

Retro (2387)

Standing, heavy load carrying and physical effort

Mamelle and Munoz[29] (1987)

CC (600)

Fatigue scorea

McDonald et al.[30] (1988)

Retro (22761)

Standing, lifting, physical efforts and fatigue scorea

Hartikainen-Sorri and Sorri[31] (1989)

CC (568)

Homer et al.[32] (1990)

Pro (773)

Heavy physical load, standing and an industrial classification based on job type Physical exertion based on job title

Teitelman et al.[33] (1990)

Pro (1206)

Job classification in three groups: standing, active or sedentary

Standing jobs associated with PB (2.72; 1.24, 5.95)

Ramirez et al.[34] (1990)

CC (6674)

Low, medium, moderately heavy, heavy or very heavy according to woman’s military occupation

Women employed in the highest levels of physical effort were at higher risk of PB (1.75; 1.12, 2.75)

PB was more common among women who stand, carry heavy loads and had considerable physical effort Work on machines (1.7; 1.01, 2.90) and mental stress (1.5; 1.03, 2.30) associated with PB. Physical exertion and posture not associated with PB Lifting associated with PB only among women who stopped working before the 28th week of gestation No association

High exertion jobs associated with PB (RR = 2.0; 1.2, 3.9)

Standing measurement based only on job title, gestational age evaluated as a mean value (no evaluation of PB as a dichotomous outcome) No control for confounders and poor statistics No control for confounding. Fatigue score is not appropriate for PA measurement

Misleading writing and analysis

Long period between delivery and interview (1 year), voluntary participation

Selection bias (sample comprised young minority women socioeconomically disadvantaged). PB estimated as birth >3 wk earlier than expected date Voluntary participation, selection bias, not every woman was interviewed at the same time, some in the first trimester and the rest were interviewed by the 20th week of gestation Some known confounders were not considered, representativeness of the sample, PA measurement, missing data

Continued next page

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Sports Med 2009; 39 (11)

Study (year)

Study design (no. of subjects)

Physical activity


Limitations

Klebanoff et al.[35] (1990)

Retro (2227)

Residency (female physicians, and wives of male physicians) occupation compared with other occupations

No association


Retro (875)

Occupational group (skilled or unskilled) was associated with PB, but not working conditions

Magann and Nolan[37] (1991)

CC (1549)

Peoples-Sheps et al.[38] (1991)

Retro (2711)

Luke et al.[39] (1995)

CC (1470)

Standing, lifting, other arduous positions and a combination of the three factors Occupational routine activities of the military Based on job title, classified into sedentary, light, medium, heavy or very heavy Physical exertion at work, standing and fatigue scorea

Long recall time, voluntary participation. The authors were unaware of the exposures among physicians’ wives. Authors discuss potential harms of OPA based on other studies (with no direct measurement) None

Savitz et al.[40] (1996)

Retro (7903)

Based only on job title

No association

Ceroń-Mireles et al.[41] (1996)

Retro (2663)

Standing and job’s physical effort

No association

Tuntiseranee et al.[42] (1998)

Pro (1797)

No association

Tuntiseranee et al.[43] (1999)

Pro (1797)

No association

Selection bias, poor measurement of PA

Escriba`-Aguïr et al.[44] (2001)

CC (576)

Physical job demand (low, moderate or high) Physical job demand (low, moderate or high) Standing, bending, kneeling, squatting, holding arms above shoulders and load carrying

Voluntary participation, high refusal rate. No adjusted data for standing and physical exertion High nonresponse rate (35%), long period (>1 y) between delivery and interview Women who stopped working due to medical problems were excluded, physical effort variables not well defined PA poorly measured

High physical exertion associated with PB (2.31; 1.43–3.73)

Newman et al.[45] (2001)

Pro (2929)

Fatigue scorea

Small sample size for the subgroup analysis might have biased results, women with some condition that excluded them from work were not included Fatigue score is not specific for studying PA

Henrich et al.[46] (2003)

CC (707)

Standing, turning, bending, kneeling, holding arms above shoulders and load carrying

No association No association

Fatigue score (above 3) associated with PB (OR = 1.4)

Spontaneous PB was associated with fatigue score only among nulliparous women No association

No direct measurement of activities, no control for confounding One year between deliveries and interviews, voluntary participation, PA measured indirectly

No control for confounders, inappropriate statistics and misleading writing

Continued next page

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Study (year)



Table I. Contd

Domingues et al.


Based on standing, work on industrial machines, physical exertion, mental stress and environmental conditions.

CC = case-control; OPA = occupational physical activities; OR = odds ratio; Pro = prospective; Retro = retrospective; RR = relative risk.

a

Small sample size, unclear and unusual definition of variables Anxiety (2.16; 1.28, 3.64) and manual work (1.70; 1.02, 2.84) associated with PB Manual work (heavy or usual) CC (400) Al-Dabbagh and Al-Taee[49] (2006)

Poor measurement of PA, representativeness of the sample Farm workers (4.2; 2.8, 6.4) and women with physical work (2.4; 1.8, 3.3) were at higher risk for PB Occupation divided into: farmers; officials or private business or students; housewives Retro (1709) Nguyen et al.[48] (2004)

None Risk factors for PB: stand >6 h/day (1.26; 1.1, 1.5), low job satisfaction (1.27; 1.1, 1.5), work >42 h/wk (1.33; 1.1, 1.6) Standing, bending, twisting, kneeling, squatting, holding arms above shoulder level and carrying heavy loads CC (6467)

Limitations


Table I. Contd

Physical activity Study design (no. of subjects) Study (year)


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comparing the results from such a pool of information. In a multicentre study[47] countries with better health conditions presented higher associations between job satisfaction and preterm birth. Conversely, as the health condition of the country decreased, the associations weakened. The same study showed that, although standing was associated with preterm birth, job dissatisfaction and long working hours presented higher odds ratios. The authors concluded that conflicting results from studies on this topic are probably due to social and legislative issues, and while a multicentre study is a unique chance to evaluate different working conditions, they also believe that contrasting work-related policies (i.e. ‘workleaves’ – when a pregnant woman stops working due to a health problem) play a role in the determination of pregnancy outcomes.

3.2 Fatigue and Job Satisfaction

Studies that evaluated pregnancy work-leaves have shown a protective association with preterm birth,[72] although it is not clear whether occupational physical activity or psychological aspects of work are making the difference. Long working hours[25,30,39,47] and shift working[71] have also been linked to preterm birth as job dissatisfaction.[46,47] Women who did not want to remain in the workforce also presented higher risks of prematurity,[73] suggesting that psychological aspects and personal fulfilment probably influence preterm birth occurrence. One of the first studies on the subject, by Mamelle et al.,[72] evaluated women from factories working under strenuous conditions, and found that work-leaves conceded, especially for fatigue (without any pathological reason), were protective against preterm birth. The protective effect of work-leaves on preterm birth seen in these studies may be an underestimate, since work-leaves may indicate pregnancy illness highly related to adverse late pregnancy outcomes. Ceroń-Mireles et al.,[41] studying Mexican women, showed that workleave was a risk factor for preterm birth, while the Sports Med 2009; 39 (11)


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Table II. Studies evaluating exclusively leisure-time physical activities (PA) and preterm birth (PB) Study (year)

Study design (no. of subjects)

Physical activity


Limitations

Hall and Kaufmann[50] (1987)

Pro (845)

Categories based on frequency of exercise (treadmill, cycling and resisted training)

No association

Small sample size, no control for confounders, self-selection bias

Clapp[51] (1990)

Pro (131)

Running and aerobics classes

No association

Small sample size, selection bias

Hatch et al.[52] (1998)

Pro (557)

Intensity codes (kcal/min) and classified as no exercise, low-moderate exercise or heavy exercise

Heavy exercise reduced PB risk (0.11; 0.02, 0.81). Less intense exercise did not affect gestational length

Voluntary participation

Hanson[53] (2001)

Pro (922)

Four categories: no exercise, strenuous exercise, nonstrenuous exercise and non-strenuous and strenuous exercise

No association

Selection bias

Evenson et al.[54] (2002)

Pro (1699)

Vigorous leisure activities performed before and during pregnancy (1st and 2nd trimester), frequency and duration for each period

Vigorous leisure activities in the 1st and even more in the 2nd trimester was associated with a reduced (but nonsignificant) risk of PB and spontaneous PB

No assessment of lightto-moderate physical activities, self-selection (to engage in vigorous activities)

Leiferman and Evenson[55] (2003)

Retro (9089)

Exercise or sports at least 3 times a week during pregnancy (yes/no)

No association

Poor assessment of PA, long interval between interview and birth (average of 17 months), voluntary participation

OR = odds ratio; Pro = prospective; Retro = retrospective.

ability to rest in the antenatal period was protective for preterm birth. 3.3 Leisure-Time Physical Activities

Studies that evaluate leisure-time physical activities typically collect information about the usual patterns (frequency, duration and intensity) and type of activity performed. Most of these studies were performed among voluntary women. The most common modalities assessed were: walking, swimming, cycling, running, weight-training, water exercises, dancing and aerobics classes. Clapp[51] found that, after 37 weeks of gestational age, active women deliver on average 6 days earlier if exercise is continued throughout ª 2009 Adis Data Information BV. All rights reserved.

late pregnancy, but no association with preterm birth was found. Hatch et al.[52] divided exercisers into low-moderate exercisers and heavy exercisers, finding that heavy exercise (above 1000 kcal/week of energy expenditure) reduced preterm birth risk, while less intense exercise did not affect gestational length. Evenson et al.[54] evaluated the role of vigorous recreational activities during the first and second trimester and preterm birth, finding nonsignificant protective effects (OR 0.80 and 95% CI 0.48, 1.35; OR 0.52 and 95% CI 0.24, 1.11, respectively). In one of the earliest studies to consider leisure-time physical activity, Berkowitz et al.[56] analysed sports activities during pregnancy and reported a protective effect of sports/exercise for Sports Med 2009; 39 (11)

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Table III. Studies evaluating simultaneously occupational, leisure-time or other physical activities (PA) and preterm birth (PB) Study design (no. of subjects)

Physical activity


Limitations

Berkowitz et al.[56] (1983)

CC (488)

Standing, carrying, lifting, housework, daily use of stairs and sports/exercises

Small sample size. Standing or moving around combined

Launer et al.[57] (1990)

Pro (15786)

Ahlborg et al.[58] (1990)

Pro (3906)

Household chores, type of work (office or manual) and position at work (standing, sitting or walking) Lifting

Sports/exercises decreased the chance for spontaneous PB (0.53; 0.36, 0.78). No association for other activities Standing (compared with sitting) was a risk for PB (1.56; 1.04, 2.60)

Klebanoff et al.[59] (1990)

Pro (7101)

Standing, heavy work/exercise and light work/exercise

Barnes et al.[60] (1991)

Pro (2741)

Household work and paid work (time and energy expenditure)

Hickey et al.[61] (1995)

Pro (1368)

Housework, recreational activities and fatigue scorea

No association

Florack et al.[62] (1995)

Pro (128)

No association

Henriksen et al.[63] (1995)

Pro (4259)

Standing, walking, bending, lifting, housekeeping and fatigue scorea Lifting, standing, walking at work and LTPA

Koemeester et al.[64] (1995)

Pro (116)

Walking, lifting, standing, bending, squatting, number of sports activities

Fortier et al.[65] (1995)

Retro (4390)

Ritsmitchai et al.[66] (1997)

CC (446)

Standing, lifting and perception of physical effort, housework and LTPA (energy expenditure) Lifting, carrying loads, standing, walking, sitting and physical exercise

Alderman et al.[67] (1998)

Retro (291)

Sports, housework and job vigorous activities (lifting, digging, carrying)

Lifting associated with PB only among women who stopped working before the 32nd week of gestation Standing associated with PB (1.31; 1.01, 1.71), heavy work/exercise not associated and light work/exercise was protective (0.59; 0.38, 0.93) Standing and higher physical stress shortened gestational age, not PB

Only crude analysis was done for LTPA. PB rate decreased as LTPA increased. For OPA, after adjustment, the combination of walking/standing at workplace presented an OR = 3.3 (1.4, 8.0) No association

No association

Physical exertion (2.91; 1.29, 6.58) and standing (4.10; 1.29, 13.10) are risk factors for PB. Physical exercise is protective (0.34; 0.16, 0.73) No association

Selection bias (women or husband had to be formally employed to have access to the clinic) None

Recreational and occupational activities combined

Unclear definition of PA, PB was not a binary outcome, only mean values of gestational age were reported Selection bias, PA at home combined standing and strenuous recreational activity Small sample size, voluntary participation Voluntary participation, exposure data collected only at the 16th week of gestation, exclusion of women with morbidities, PB rate higher among refusals Voluntary participation, gestational age evaluated as a continuous variable, convenience sample, small sample Misleading writing (variables definition) and voluntary participation Small sample size, recruitment in a single maternity hospital

Small sample size, only 2nd trimester PA was considered. All PAs combined Continued next page

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Sports Med 2009; 39 (11)

Study (year)

Based on standing, work on industrial machines, physical exertion, mental stress and environmental conditions.

CC = case-control; LTPA = leisure-time physical activities; OPA = occupational physical activities; OR = odds ratio; Pro = prospective; Retro = retrospective.

a

High nonresponse rate (39%). Data only on 1st and 2nd trimester LTPA protects against PB (only crude analysis). No association for standing and lifting


Vigorous LTPA, standing and lifting CC (1908) Pompeii et al.[71] (2005)

Voluntary participation, high refusal rate LTPA not associated with PB. OPA is a risk factor for the whole sample (1.94; 1.13, 3.35) and among nulliparous (4.16; 1.59, 10.83). Among multiparous, housework protects against PB OPA, LTPA, school activities and housework Retro (1714) Cavalli and Tanaka[70] (2001)

Small sample size, poor PA measurement Extreme prematurity is inversely associated with regular LTPA Regular LTPA and physical exertion CC (245) Petridou et al.[69] (2001)

Standing combined with moving on the job, selection bias, only data from 1st and 2nd trimester were analysed Stair climbing (1.60; 1.05, 2.46) and walking for a purpose (2.10; 1.38, 2.20) were risks, while LTPA was protective for PB (0.51; 0.27, 0.95) LTPA, job and housework activities (lifting, standing, climbing stairs and walking for a purpose) Pro (1166) Misra et al.[68] (1998)

Limitations Physical activity Study design (no. of subjects) Study (year)

Table III. Contd

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spontaneous preterm birth. Four other studies[59,63,66,68] also found that recreational activities were associated with a reduced incidence of preterm birth. Pompeii et al.[71] found similar protective effects for leisure-time physical activity, but only a crude analysis was carried out. From the papers reviewed, not a single study showed a detrimental effect of recreational activities concerning preterm birth. Overall, studies show that either recreational activities are associated with less chance of preterm birth[52,54,56,63,66,68] or at least do not affect this outcome.[50,51,53,55,64,65,70] 3.4 All-Domain or Other Physical Activities

One way to measure physical activity when assessing more than one kind of activity is through total energy expenditure. This method has been used in pregnant[60,74-76] and nonpregnant samples.[77] Energy expenditure can be assessed by accelerometers, double-labelled water or questionnaires.[78,79] However, all these procedures share the same characteristic of not explaining how the energy was used. Another type of study evaluates physical activities as a single measure, usually a score of activity. Instruments like the International Physical Activity Questionnaire (IPAQ)[80] or the Physical Activity Recall (PAR)[81] are designed to measure physical activity based on the amount of activity performed during specific periods (e.g. for a week) and to consider all domains of physical activity: occupational, commuting, household and leisure time. This type of instrument could be used during pregnancy as long as the interview is repeated several times during gestation to capture changes in activity patterns from conception to delivery. If one decides to interview women during pregnancy and to measure physical activity based on 7-day recall information, the stage of gestation would influence the results, and the information from a single moment would underestimate or overestimate physical activity levels for the whole pregnancy. Four of the studies evaluated[60-62,67] considered physical activity as energy expenditure or as a single score, including occupational physical activity, leisure-time physical activity and housework. Sports Med 2009; 39 (11)

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No association between physical activity and preterm birth was reported in these studies. Household activities were also not associated with prematurity. Contrary to previous studies,[59-61,67] physical activity questionnaires that combine all domains of physical activity in a single score do not seem suitable to study some pregnancy outcomes. Clearly, occupational, household and leisure activities may have different effects. Therefore, we cannot see physical activity as a whole, unless we are studying outcomes that are influenced primarily by energy expenditure balance, which may be appropriate to study, for example, maternal weight gain, fetal growth or birthweight. However, this does not seem to be the case for preterm birth. 4. Limitations Found in the Reviewed Literature Sampling was a weakness in many studies. Convenience samples obtained from a single maternity ward,[25,27,69] from the private sector[33] or from women voluntarily responding to a mailed questionnaire[39,40,52,55] may not be representative of a population. Although we identified papers that explored large datasets[30,34,40,47,55,57,59] with thousands of women, only one study[39] provided a sample size calculation and another[41] provided an estimate of statistical power. Without a sample size or power calculation it is not possible to adequately interpret a lack of association – it may simply be due to lack of statistical power and not evidence against an association. There is no need for a representative sample to be used to study biological outcomes, but, as discussed by Marbury,[82] some papers base their conclusions on risk calculations using very small and selected groups[26,28,30] (e.g. developed-country studies dividing women into job-demand categories and high-demand categories are usually very small) resulting in comparisons between categories that are flawed or applicable only to specific populations. Different working conditions worldwide might lead us to conflicting conclusions, regardless of study quality, methodology or real effects being evaluated. Living conditions and culture may reª 2009 Adis Data Information BV. All rights reserved.

sult in women rating the physical effort they perform differently in a way that epidemiological effects may not be directly comparable: what is seen as a strenuous effort to an American woman might be considered a usual task to another woman living in Thailand, for instance. Another point is that a woman whose colleagues’ working conditions are strenuous may consider her tasks less tiring than if we compared the same job among women working in less physically demanding jobs.[29] A woman who usually works under high physical demands and suddenly changes her job tasks to less demanding ones may classify herself in the low-effort category, although she still experiences high efforts. In addition, when reviewing studies written over a long timespan we must consider that working conditions may be changing and what was considered strenuous in 1995 may not be in 2005 or in 1985.[36] In addition, there may be a self-selection bias in occupational studies where women who keep on working standing for long periods during the third trimester are less likely to have experienced medical problems and therefore present lower risk for adverse outcomes. The best way to assess the potential ‘healthy worker effect’ would be to follow up women who gave up working in the same manner as the working women, and to evaluate whether the reasons for preterm birth differ between both groups.

5. Physiological Aspects of Physical Activities in Pregnancy During prolonged standing, pregnant women experience circulation adaptations: the relaxed uterus inhibits venous flow to the right ventricle by compression and fetal heart rate seems to increase.[83] Little evidence is available about lifting weights, and epidemiological studies do not discuss the issue deeply. However, unless a woman stops breathing during lifting extremely heavy weights (valsalva manoeuvre[84]), there is no reason to believe that daily activities of lifting could result in any adaptation or blood flow alteration that could be related to an increase in the likelihood of preterm birth. Sports Med 2009; 39 (11)


The literature describes many benefits of recreational physical activity during pregnancy:[85,86] more adequate weight gains, improvements in mood and self-esteem,[87] better body image, less anxiety and depressive symptoms among exercising women,[88-90] faster labour, better blood circulation (including blood perfusion to the placenta[91] and venous return from lower limbs, preventing swelling of the extremities), less constipation, better muscular support to the pelvis (leading to less chance of urinary incontinence[92]), better diabetes and hypertension control[93] and less low back pain complaints,[94] among others. Most of the potential effects of leisure-time physical activity on preterm birth prevention are thought to be indirect, as some known risk factors for preterm birth are preventable or reduced by regular exercise, such as excessive weight gain, depression and arterial hypertension.[86] With regard to pre-eclampsia, decreases in proinflammatory cytokines and leptin, lower oxidative stress and improved lipoprotein concentrations are also potential effects of exercise in pregnancy.[86] 6. Physical Activity and Preterm Birth: Considerations Physical activity is a complex factor to assess in epidemiological studies with pregnant or nonpregnant populations, and even the same activity (type, frequency and duration) can result in distinct physiological effects depending on several factors such as environment, intensity, nutrition status, willingness to exercise, period of gestation and previous training.[95] To illustrate the adaptation principle, a 5 km run may be unthinkable for most women (pregnant or not) but for a few well-conditioned people it might be an ordinary exercise session, easily carried out in the fifth month of pregnancy. On an occupational level, if a woman usually works standing 8 hours a day and suddenly reduces her shifts to 4 hours, her effort level will probably not be the same as that experienced by another woman who recently moved from a sedentary job to one where she works standing 4 hours; although, if we interview both, the exposure will be the same – 4 hours daily of standing work. ª 2009 Adis Data Information BV. All rights reserved.

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Most leisure-time physical activity studies rely on information from voluntary women or select groups of women.[50,51,96,97] We cannot rule out the chance that there might be a tendency for healthier women to exercise more than high-risk women,[60] which may affect the results. Leisure-time physical activity might protect against preterm birth because recreationally active women might have a favourable psychological profile and be more concerned about their overall health and other factors not easily controlled in an epidemiological study. Moreover, causation of preterm birth is multifactorial, with many of its determinants still unknown.[6] Underlying risk factors for preterm birth may be those psychological aspects of occupations where women are under constant stress and/or socioeconomic factors not completely assessed by researchers.[59,82] Usually, jobs that are physically demanding are also the ones with less control over decisions and with the lowest levels of satisfaction. There is no clear evidence in the literature that the standing position is harmful to pregnant women as regards preterm labour. The transitory physiological changes of the upright posture are unlikely to have a significant impact on premature rupture of the membranes or birth. When dealing specifically with leisure-time physical activity, some aspects of reverse causality must be considered, especially concerning psychological features. It is reasonable to suppose that depression might lead to isolation and inactivity, an idea supported by a recent literature review.[89] In addition, depressed women present with a higher incidence of preterm birth.[18,98] Barnes et al.[60] suggested that healthier women tend to exercise more than high-risk women, another association that could lead to reverse causality when studying pregnancy adverse outcomes, although other researchers[66] have found a protective effect of leisure-time physical activity independent of pregnancy complications. Many papers have discussed the benefits of physical activity regarding hypertension prevention.[86,99,100] When considering preterm birth it is reasonable to believe that hypertension prevention indirectly prevents preterm birth, since active lifestyles are thought to be beneficial for blood Sports Med 2009; 39 (11)

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pressure and arterial hypertension, and it is a well known risk factor for prematurity. According to a recent roundtable held by the American College of Sports Medicine, physical activity may reduce the risk of pre-eclampsia through several physiological and metabolic pathways. Data reviewed by the group provided evidence to support the biological plausibility of using recreational physical activity to prevent pre-eclampsia in pregnant women.[86] Other researchers have reached similar conclusions.[101,102] Another consideration regarding leisure-time physical activity is that women with a preterm history might avoid physical effort (whether advised by health personnel or not). Regardless of physical activity status, these are women at higher risk of preterm birth, because preterm birth history and other past obstetric risk factors are strong predictors for prematurity. This does not apply to occupational activities, depending on working conditions; to change occupational tasks might not be an option. Although many countries’ legislation assure special treatment for pregnant women, we know that poor working conditions do not allow for changes, especially in developing countries where women must work throughout gestation to survive. If occupational exposures do affect preterm birth it is probably through physiological and biomechanical mechanisms working during the second and third trimesters, when fetal size becomes a physical load and circulation adaptations discussed previously begin. If that is true, results from studies that evaluated only activities at the beginning of gestation[67,33] should be taken cautiously. With regard to leisure activities, the possible effects are not immediate, since the idea we support here is that the exercise acts mainly by improving women’s overall health. Physical activity assessment would be better classified if some in loco observation was carried out, especially to evaluate occupational activities. This strategy would help to avoid recall bias and bias from a woman’s self-perception of physical effort. Stress sources, although difficult to measure, should be investigated to isolate harmful effects of psychological aspects and not to mix them with other aspects of poor working conditions. ª 2009 Adis Data Information BV. All rights reserved.

With respect to control of confounding factors, at least the following variables must be considered: age, race, parity, socioeconomic characteristics, obstetric history and pregnancy-related illnesses such as infections and hypertension. 7. Conclusions Given the evidence provided by the reviewed literature concerning leisure-time physical activity and prematurity, it is safe to assume there is no risk involved for normal pregnancies. Pregnant active women should not be advised to stop exercising, and intensity reduction should be according to the woman’s perception, assuming that the gestational development is normal. Sedentary women should be encouraged to start a physical activity programme compatible with their fitness levels and clinical status. Adequate leisure-time physical activity during pregnancy is also indicated to prevent excessive weight gain, and to control risk factors such as hypertension and diabetes.[99,100] Regarding occupational physical activities, although there is a high variation of exposure among the occupations studied, it seems that, if working conditions are adequate, the negative effect of working during pregnancy is due to psychological features and not physical workload. Thus, pregnant women do not need to be systematically taken away from physically demanding activities fearing that this would increase their risk of premature deliveries. In any case, pregnant women should enrol in high quality antenatal care early on, and the advice from the health team, based on the particular characteristics of each woman and pregnancy, must be followed at all times. The well-being of the future mother is also a priority during working hours. Finally, it is essential that the many methodological issues raised in the present review are dealt with in the planning of future studies so that they can provide us with more conclusive results regarding physical activity and pregnancy outcomes. Acknowledgements No sources of funding were used to assist in the preparation of this review. The authors have no conflicts of interest

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that are directly relevant to the content of this review. During the preparation of the paper, MRD received a fellowship from the CNPq (Brazilian National Council for Scientific and Technological Development).

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References 1. Slattery MM, Morrison JJ. Preterm delivery. Lancet 2002 Nov 9; 360 (9344): 1489-97 2. Steer P. The epidemiology of preterm labour. BJOG 2005 Mar; 112 Suppl. 1: 1-3 3. Martin JA, Hamilton BE, Sutton PD, et al. Births: final data for 2004. Natl Vital Stat Rep 2006 Sep 29; 55 (1): 1-101 4. Vogel I, Thorsen P, Curry A, et al. Biomarkers for the prediction of preterm delivery. Acta Obstet Gynecol Scand 2005 Jun; 84 (6): 516-25 5. Goldenberg RL, Rouse DJ. Prevention of premature birth. N Engl J Med 1998 Jul 30; 339 (5): 313-20 6. Committee on Understanding Premature Birth and Assuring Health Outcomes Board on Healthy Sciences Policy. Preterm birth: causes, consequences and prevention. Washington, DC: National Academies Press Institute of Medicine, 2006 7. Iams JD. The epidemiology of preterm birth. Clin Perinatol 2003 Dec; 30 (4): 651-64 8. Tucker J, McGuire W. Epidemiology of preterm birth. BMJ 2004 Sep 18; 329 (7467): 675-8 9. Wen SW, Smith G, Yang Q, et al. Epidemiology of preterm birth and neonatal outcome. Semin Fetal Neonatal Med 2004 Dec; 9 (6): 429-35 10. Savitz DA, Kaufman JS, Dole N, et al. Poverty, education, race, and pregnancy outcome. Ethn Dis 2004 Summer; 14 (3): 322-9 11. Jacobsson B, Ladfors L, Milsom I. Advanced maternal age and adverse perinatal outcome. Obstet Gynecol 2004 Oct; 104 (4): 727-33 12. Pollack H, Lantz PM, Frohna JG. Maternal smoking and adverse birth outcomes among singletons and twins. Am J Pub Health 2000 Mar; 90 (3): 395-400 13. Ananth CV, Getahun D, Peltier MR, et al. Recurrence of spontaneous versus medically indicated preterm birth. Am J Obstet Gynecol 2006 Sep; 195 (3): 643-50 14. Andrews WW, Hauth JC, Goldenberg RL. Infection and preterm birth. Am J Perinatol 2000; 17 (7): 357-65 15. Barros FC, Victora CG, Barros AJ, et al. The challenge of reducing neonatal mortality in middle-income countries: findings from three Brazilian birth cohorts in 1982, 1993, and 2004. Lancet 2005 Mar 5-11; 365 (9462): 847-54 16. Dole N, Savitz DA, Hertz-Picciotto I, et al. Maternal stress and preterm birth. Am J Epidemiol 2003 Jan 1; 157 (1): 14-24 17. Copper RL, Goldenberg RL, Das A, et al. The preterm prediction study: maternal stress is associated with spontaneous preterm birth at less than thirty-five weeks’ gestation. National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network. Am J Obstet Gynecol 1996 Nov; 175 (5): 1286-92 18. Dayan J, Creveuil C, Marks MN, et al. Prenatal depression, prenatal anxiety, and spontaneous preterm birth: a pro-


21.

22. 23. 24.

25.

26.

27.

28.

29.

30.

31.

32.

33.

34.

35.

36.

spective cohort study among women with early and regular care. Psychosom Med 2006 Nov-Dec; 68 (6): 938-46 Moutquin JM. Classification and heterogeneity of preterm birth. Brit J Gynaecol 2003 Apr; 110 Suppl. 20: 30-3 Raju TN. Epidemiology of late preterm (near-term) births [abstract no. vii]. Clin Perinatol 2006 Dec; 33 (4): 751-63 Dole Dobak WJ, Gardner MO. Late preterm gestation: physiology of labor and implications for delivery. Clin Perinatol 2006 Dec; 33 (4): 765-76 Exercise during pregnancy and the postpartum period. Clin Obstet Gynecol 2003 Jun; 46 (2): 496-9 Camporesi EM. Diving and pregnancy. Semin Perinatol 1996 Aug; 20 (4): 292-302 ACOG Committee. Exercise during pregnancy and the postpartum period [opinion]: number 267, January 2002. American College of Obstetricians and Gynecologists. Int J Gynaecol Obstet 2002 Apr; 77 (1): 79-81 Mamelle N, Laumon B, Lazar P. Prematurity and occupational activity during pregnancy. Am J Epidemiol 1984 Mar; 119 (3): 309-22 Saurel-Cubizolles MJ, Kaminski M, Llado-Arkhipoff J, et al. Pregnancy and its outcome among hospital personnel according to occupation and working conditions. J Epidemiol Community Health 1985 Jun; 39 (2): 129-34 Zuckerman BS, Frank DA, Hingson R, et al. Impact of maternal work outside the home during pregnancy on neonatal outcome. Pediatrics 1986 Apr; 77 (4): 459-64 Saurel-Cubizolles MJ, Kaminski M. Pregnant women’s working conditions and their changes during pregnancy: a national study in France. Br J Ind Med 1987 Apr; 44 (4): 236-43 Mamelle N, Munoz F. Occupational working conditions and preterm birth: a reliable scoring system. Am J Epidemiol 1987 Jul; 126 (1): 150-2 McDonald AD, McDonald JC, Armstrong B, et al. Prematurity and work in pregnancy. Br J Ind Med 1988 Jan; 45 (1): 56-62 Hartikainen-Sorri AL, Sorri M. Occupational and sociomedical factors in preterm birth. Obstet Gynecol 1989 Jul; 74 (1): 13-6 Homer CJ, Beresford SA, James SA, et al. Work-related physical exertion and risk of preterm, low birthweight delivery. Paediatr Perinat Epidemiol 1990 Apr; 4 (2): 161-74 Teitelman AM, Welch LS, Hellenbrand KG, et al. Effect of maternal work activity on preterm birth and low birth weight. Am J Epidemiol 1990 Jan; 131 (1): 104-13 Ramirez G, Grimes RM, Annegers JF, et al. Occupational physical activity and other risk factors for preterm birth among US Army primigravidas. Am J Pub Health 1990 Jun; 80 (6): 728-30 Klebanoff MA, Shiono PH, Rhoads GG. Outcomes of pregnancy in a national sample of resident physicians. N Engl J Med 1990 Oct 11; 323 (15): 1040-5 Saurel-Cubizolles MJ, Subtil D, Kaminski M. Is preterm delivery still related to physical working conditions in pregnancy? J Epidemiol Community Health 1991 Mar; 45 (1): 29-34

Sports Med 2009; 39 (11)

974

37. Magann EF, Nolan TE. Pregnancy outcome in an activeduty population. Obstet Gynecol 1991 Sep; 78 (3 Pt 1): 391-3 38. Peoples-Sheps MD, Siegel E, Suchindran CM, et al. Characteristics of maternal employment during pregnancy: effects on low birthweight. Am J Pub Health 1991 Aug; 81 (8): 1007-12 39. Luke B, Mamelle N, Keith L, et al. The association between occupational factors and preterm birth: a United States nurses’ study. Research Committee of the Association of Women’s Health, Obstetric, and Neonatal Nurses. Am J Obstet Gynecol 1995 Sep; 173 (3 Pt 1): 849-62 40. Savitz DA, Olshan AF, Gallagher K. Maternal occupation and pregnancy outcome. Epidemiology 1996 May; 7 (3): 269-74 41. Ceroń-Mireles P, Harlow SD, Sanchez-Carrillo CI. The risk of prematurity and small-for-gestational-age birth in Mexico City: the effects of working conditions and antenatal leave. Am J Pub Health 1996 Jun; 86 (6): 825-31 42. Tuntiseranee P, Geater A, Chongsuvivatwong V, et al. The effect of heavy maternal workload on fetal growth retardation and preterm delivery: a study among southern Thai women. J Occup Environ Med 1998 Nov; 40 (11): 1013-21 43. Tuntiseranee P, Olsen J, Chongsuvivatwong V, et al. Socioeconomic and work related determinants of pregnancy outcome in southern Thailand. J Epidemiol Community Health 1999 Oct; 53 (10): 624-9 44. Escriba`-Aguïr V, Perez-Hoyos S, Saurel-Cubizolles MJ. Physical load and psychological demand at work during pregnancy and preterm birth. Int Arch Occup Environ Health 2001 Oct; 74 (8): 583-8 45. Newman RB, Goldenberg RL, Moawad AH, et al. Occupational fatigue and preterm premature rupture of membranes: National Institute of Child Health and Human Development Maternal-Fetal Medicine, Units Network. Am J Obstet Gynecol 2001 Feb; 184 (3): 438-46 46. Henrich W, Schmider A, Fuchs I, et al. The effects of working conditions and antenatal leave for the risk of premature birth in Berlin. Arch Gynecol Obstet 2003 Nov; 269 (1): 37-9 47. Saurel-Cubizolles MJ, Zeitlin J, Lelong N, et al. Employment, working conditions, and preterm birth: results from the Europop case-control survey. J Epidemiol Community Health 2004 May; 58 (5): 395-401 48. Nguyen N, Savitz DA, Thorp JM. Risk factors for preterm birth in Vietnam. Int J Gynaecol Obstet 2004 Jul; 86 (1): 70-8 49. Al-Dabbagh SA, Al-Taee WY. Risk factors for pre-term birth in Iraq: a case-control study. BMC Pregnancy Childbirth 2006; 6: 13 50. Hall DC, Kaufmann DA. Effects of aerobic and strength conditioning on pregnancy outcomes. Am J Obstet Gynecol 1987 Nov; 157 (5): 1199-203 51. Clapp 3rd JF. The course of labor after endurance exercise during pregnancy. Am J Obstet Gynecol 1990 Dec; 163 (6 Pt 1): 1799-805 52. Hatch M, Levin B, Shu XO, et al. Maternal leisure-time exercise and timely delivery. Am J Pub Health 1998 Oct; 88 (10): 1528-33


Domingues et al.

53. Hanson S. The effects of maternal exercise, depression and stress on preterm birth in low income, African American women [doctoral thesis]. Baltimore (MD): Johns Hopkins University, 2001 54. Evenson KR, Siega-Riz AM, Savitz DA, et al. Vigorous leisure activity and pregnancy outcome. Epidemiology 2002 Nov; 13 (6): 653-9 55. Leiferman JA, Evenson KR. The effect of regular leisure physical activity on birth outcomes. Matern Child Health J 2003 Mar; 7 (1): 59-64 56. Berkowitz GS, Kelsey JL, Holford TR, et al. Physical activity and the risk of spontaneous preterm delivery. J Reprod Med 1983 Sep; 28 (9): 581-8 57. Launer LJ, Villar J, Kestler E, et al. The effect of maternal work on fetal growth and duration of pregnancy: a prospective study. Br J Obstet Gynaecol 1990 Jan; 97 (1): 62-70 58. Ahlborg Jr G, Bodin L, Hogstedt C. Heavy lifting during pregnancy: a hazard to the fetus? A prospective study. Int J Epidemiol 1990 Mar; 19 (1): 90-7 59. Klebanoff MA, Shiono PH, Carey JC. The effect of physical activity during pregnancy on preterm delivery and birth weight. Am J Obstet Gynecol 1990 Nov; 163 (5 Pt 1): 1450-6 60. Barnes DL, Adair LS, Popkin BM. Women’s physical activity and pregnancy outcome: a longitudinal analysis from the Philippines. Int J Epidemiol 1991 Mar; 20 (1): 162-72 61. Hickey CA, Cliver SP, Mulvihill FX, et al. Employmentrelated stress and preterm delivery: a contextual examination. Pub Health Rep 1995 Jul-Aug; 110 (4): 410-8 62. Florack EI, Pellegrino AE, Zielhuis GA, et al. Influence of occupational physical activity on pregnancy duration and birthweight. Scand J Work Environ Health 1995 Jun; 21 (3): 199-207 63. Henriksen TB, Hedegaard M, Secher NJ, et al. Standing at work and preterm delivery. Br J Obstet Gynaecol 1995 Mar; 102 (3): 198-206 64. Koemeester AP, Broersen JP, Treffers PE. Physical work load and gestational age at delivery. Occup Environ Med 1995 May; 52 (5): 313-5 65. Fortier I, Marcoux S, Brisson J. Maternal work during pregnancy and the risks of delivering a small-for-gestational-age or preterm infant. Scand J Work Environ Health 1995 Dec; 21 (6): 412-8 66. Ritsmitchai S, Geater A, Chongsuviwatvong V. Prolonged standing and physical exertion at work during pregnancy increases the risk of preterm birth for Thai mothers. J Occup Health 1997; 39: 217-22 67. Alderman BW, Zhao H, Holt VL, et al. Maternal physical activity in pregnancy and infant size for gestational age. Ann Epidemiol 1998 Nov; 8 (8): 513-9 68. Misra DP, Strobino DM, Stashinko EE, et al. Effects of physical activity on preterm birth. Am J Epidemiol 1998 Apr 1; 147 (7): 628-35 69. Petridou E, Salvanos H, Skalkidou A, et al. Are there common triggers of preterm deliveries? BJOG 2001 Jun; 108 (6): 598-604

Sports Med 2009; 39 (11)


70. Cavalli A, Tanaka T. Relationship between maternal physical activities and preterm birth. Environ Health Preventive Med 2001; 6 (Jul): 74-81 71. Pompeii LA, Savitz DA, Evenson KR, et al. Physical exertion at work and the risk of preterm delivery and smallfor-gestational-age birth. Obstet Gynecol 2005 Dec; 106 (6): 1279-88 72. Mamelle N, Bertucat I, Munoz F. Pregnant women at work: rest periods to prevent preterm birth? Paediatr Perinat Epidemiol 1989 Jan; 3 (1): 19-28 73. Homer CJ, James SA, Siegel E. Work-related psychosocial stress and risk of preterm, low birthweight delivery. Am J Pub Health 1990 Feb; 80 (2): 173-7 74. Perkins CC, Pivarnik JM, Paneth N, et al. Physical activity and fetal growth during pregnancy. Obstet Gynecol 2007 Jan; 109 (1): 81-7 75. Stein AD, Rivera JM, Pivarnik JM. Measuring energy expenditure in habitually active and sedentary pregnant women. Med Sci Sports Exerc 2003 Aug; 35 (8): 1441-6 76. Magann EF, Evans SF, Newnham JP. Employment, exertion, and pregnancy outcome: assessment by kilocalories expended each day. Am J Obstet Gynecol 1996 Jul; 175 (1): 182-7 77. Campbell KL, Crocker PR, McKenzie DC. Field evaluation of energy expenditure in women using Tritrac accelerometers. Med Sci Sports Exerc 2002 Oct; 34 (10): 1667-74 78. Leenders N, Sherman WM, Nagaraja HN. Comparisons of four methods of estimating physical activity in adult women. Med Sci Sports Exerc 2000 Jul; 32 (7): 1320-6 79. Hoos MB, Plasqui G, Gerver WJ, et al. Physical activity level measured by doubly labeled water and accelerometry in children. Eur J Appl Physiol 2003 Aug; 89 (6): 624-6 80. Craig CL, Marshall AL, Sjostrom M, et al. International physical activity questionnaire: 12-country reliability and validity. Med Sci Sports Exerc 2003 Aug; 35 (8): 1381-95 81. Hayden-Wade HA, Coleman KJ, Sallis JF, et al. Validation of the telephone and in-person interview versions of the 7-day PAR. Med Sci Sports Exerc 2003 May; 35 (5): 801-9 82. Marbury MC. Relationship of ergonomic stressors to birthweight and gestational age. Scand J Work Environ Health 1992 Apr; 18 (2): 73-83 83. Schneider KT, Deckardt R. The implication of upright posture on pregnancy. J Perinat Med 1991; 19 (1-2): 121-31 84. Gorgulu S, Eksik A, Eren M, et al. Assessment of the effects of various maneuvers on both atrial pressure changes. Int J Cardiol 2003 Dec; 92 (2-3): 241-5 85. Brown W. The benefits of physical activity during pregnancy. J Sci Med Sport 2002 Mar; 5 (1): 37-45 86. Impact of physical activity during pregnancy and postpartum on chronic disease risk. Med Sci Sports Exerc 2006 May; 38 (5): 989-1006 87. Da Costa D, Rippen N, Dritsa M, et al. Self-reported leisure-time physical activity during pregnancy and relationship to psychological well-being. J Psychosom Obstet Gynaecol 2003 Jun; 24 (2): 111-9


975

88. Poudevigne MS, O’Connor PJ. Physical activity and mood during pregnancy. Med Sci Sports Exerc 2005 Aug; 37 (8): 1374-80 89. Poudevigne MS, O’Connor PJ. A review of physical activity patterns in pregnant women and their relationship to psychological health. Sports Med 2006; 36 (1): 19-38 90. Boscaglia N, Skouteris H, Wertheim EH. Changes in body image satisfaction during pregnancy: a comparison of high exercising and low exercising women. Aust N Z J Obstet Gynaecol 2003 Feb; 43 (1): 41-5 91. Clapp JF. Influence of endurance exercise and diet on human placental development and fetal growth. Placenta 2006 Jun-Jul; 27 (6-7): 527-34 92. Sampselle CM, Miller JM, Mims BL, et al. Effect of pelvic muscle exercise on transient incontinence during pregnancy and after birth. Obstet Gynecol 1998 Mar; 91 (3): 406-12 93. Dempsey JC, Butler CL, Williams MA. No need for a pregnant pause: physical activity may reduce the occurrence of gestational diabetes mellitus and preeclampsia. Exerc Sport Sci Rev 2005 Jul; 33 (3): 141-9 94. Granath AB, Hellgren MS, Gunnarsson RK. Water aerobics reduces sick leave due to low back pain during pregnancy. J Obstet Gynecol Neonatal Nurs 2006 Jul-Aug; 35 (4): 465-71 95. Wolfe LA, Hall P, Webb KA, et al. Prescription of aerobic exercise during pregnancy. Sports Med 1989 Nov; 8 (5): 273-301 96. Narendran S, Nagarathna R, Narendran V, et al. Efficacy of yoga on pregnancy outcome. J Altern Complement Med 2005 Apr; 11 (2): 237-44 97. Duncombe D, Skouteris H, Wertheim EH, et al. Vigorous exercise and birth outcomes in a sample of recreational exercisers: a prospective study across pregnancy. Aust N Z J Obstet Gynaecol 2006; 46 (4): 288-92 98. Orr ST, James SA, Blackmore Prince C. Maternal prenatal depressive symptoms and spontaneous preterm births among African-American women in Baltimore, Maryland. Am J Epidemiol 2002; 156 (9): 797-802 99. Catalano PM. Management of obesity in pregnancy. Obstet Gynecol 2007 Feb; 109 (2 Pt 1): 419-33 100. Kuehn BM. Groups take aim at US preterm birth rate. JAMA 2006 Dec 27; 296 (24): 2907-8 101. Hegaard HK, Pedersen BK, Nielsen BB, et al. Leisure time physical activity during pregnancy and impact on gestational diabetes mellitus, pre-eclampsia, preterm delivery and birth weight: a review. Acta Obstet Gynecol Scand 2007; 86 (11): 1290-6 102. Weissgerber TL, Wolfe LA, Davies GA, et al. Exercise in the prevention and treatment of maternal-fetal disease: a review of the literature. Appl Physiol Nutr Metab 2006 Dec; 31 (6): 661-74

Correspondence: Marlos Rodrigues Domingues, PhD, Rua Pedro Armando Gatti, 158-Jardim do Sol., CEP 96216-080, Rio Grande/RS, Brazil. E-mail: [email protected]

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MyJalah, Edisi 11 - November 2009

Spektrum der Wissenschaft November 2004 issue 11

Spektrum der Wissenschaft November 2006 issue 11

sports medicine Volume 41 Issue 9 September 2011

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