Independent Study Course 18.3.1

Epidemiology of Dance Injuries:

Biopsychosocial Considerations in the

Management of

Dancer Health

An Independent Study Course Designed

for Individual Continuing Education

Dance Medicine: Strategiesfor the Prevention and Care ofInjuries to Dancers

Marijeanne Liederbach, PT, PhD, ATC, CSCSHarkness Center for Dance InjuriesNYU Hospital for Joint Diseases

New York, New York

Dance Medicine: Strategiesfor the Prevention and Care of Injuries to DancersChristopher Hughes, PT, PhD, OCS—Editor

2920 East Avenue South, Suite 200 | La Crosse, WI 54601 | Office 608-788-3982 | Toll Free 800-444-3982 | Fax 608-788-3965

Dear Colleague,

I am pleased to welcome you to the monograph Epidemiology of Dance Injuries: Biopsychosocial Considerations in the Management of Dancer Health by Marijeanne Liederbach, PT, PhD, ATC, CSCS. This monograph is part of the Orthopaedic Section Independent Study Course series 18.3, titled Dance Medicine: Strategies for the Prevention and Care of Injuries to Dancers.

Marijeanne Liederbach is the director of research and education for the Harkness Center for Dance Injuries at the New York University Medical Center Hospital for Joint Diseases. Prior to her current appointment, Dr Liederbach headed the dance medicine services for The Joffrey Ballet for 10 years while also serving as supervisor of sports physical therapy at the Nicholas Institute of Sports Medicine and Athletic Trauma at Lenox Hill Hospital and instructor of kinesiology at Columbia University. She has a bachelor of arts degree in dance, a bachelor of science degree in health sciences, 2 master of science degrees, one in physical education and sports medicine and one in physical therapy, and a doctorate degree in biomechanics and ergonomics. Dr Liederbach is the owner of PT Plus P.C., a private physical therapy practice in the landmark City Center building in New York City.

Dr Liederbach has provided backstage therapy for hundreds of dancers, dance companies, and Broadway shows. She has also authored numerous papers and chapters, as well as lectured internationally on topics pertaining to the prevention and care of dance injuries. She is a member of the editorial review board of the Journal of Dance Medicine and Science, the DanceUSA task force on dancer health, the performing arts special interest group of the Orthopaedic Section within the American Physical Therapy Association, and a past member of the national advisory committee for the American Physical Therapy Association’s performing arts practice analysis. She is also an affiliate member of the American Orthopaedic Society for Sports Medicine, a founding member and former board member of the International Association for Dance Medicine, and current chair of its standard measures consensus initiative on screening, injury reporting, and measurement of function. Prior to her career in dance medicine, Dr Liederbach danced professionally for many years and worked as a choreographer. Her critically acclaimed work has been shown in Europe and throughout the United States.

In her monograph, Dr Liederbach describes the socioeconomic and psychological factors that influence the culture and occupational demands of dance and their impact on dance injury. Her perspective is not just as a researcher, but also as a professional dancer and lifelong teacher of dance. The author’s blending of these backgrounds is a great benefit to clinicians who wish to effectively treat dance injury. Without understanding the culture of dance, one can only scratch the surface in terms of achieving clinical effectiveness in treat-ing injuries in dance. Not only does Dr Liederbach evaluate ergonomic risk within the dance workplace, but she provides the reader with strategies for effective modification. She also discusses the value and limits of the screening process and its role in the broader context of prevention and intervention. Dr Liederbach also shares her knowledge of choosing the appropriate therapeutic techniques that can effectively restore function and minimize risk for reinjury.

The goal of this monograph is to shed light on how biopsychosocial factors influence best practice to prevent, diagnose, rehabilitate, and enhance the health and functional abilities of members of the dance community. I think Dr Liederbach has done just that! I am confident you will feel the same. My sincere thanks to Dr Liederbach for serving as author of 2 monographs in this course series and for mobilizing her professional colleagues to write for other monographs in the series.

Sincerely,

Christopher Hughes, PT, PhD, OCS, CSCSEditor

Photo courtesy of Frank Capri, PhotographerJete en attitude-–Mayuko Shoka, Dance Theatre of Harlem Ensemble

TABLE OF CONTENTS

LEARNING OBJECTIVES ..................................................................................................................................................1

INTRODUCTION ............................................................................................................................................................1

EPIDEMIOLOGY OF INJURIES IN DANCE ......................................................................................................................1

Risk ........................................................................................................................................................................1

Prevalence ..............................................................................................................................................................1

Incidence ................................................................................................................................................................2

Work-related Musculoskeletal Disorders .................................................................................................................2

Injury Distribution by Anatomic Region ..................................................................................................................2

Injury Distribution by Other Factors ........................................................................................................................3

Sex .................................................................................................................................................................3

Age and skill ....................................................................................................................................................3

Exposure ..........................................................................................................................................................4

Personal factors ................................................................................................................................................4

When do injuries happen? ................................................................................................................................4

Time Lost From Injuries ...........................................................................................................................................4

Cost of Injuries ........................................................................................................................................................4

ETIOLOGY ......................................................................................................................................................................4

Cause .....................................................................................................................................................................4

Risk Factors in Dance..............................................................................................................................................5

Occupational Demands of Dance ...........................................................................................................................5

Selection of Dancers ...............................................................................................................................................6

Physical Tendencies ................................................................................................................................................6

Mobility ...........................................................................................................................................................6

Selective muscle tightness and weakness ..........................................................................................................6

Thinness and low energy expenditure ...............................................................................................................6

Psychological Tendencies ........................................................................................................................................7

Personality ........................................................................................................................................................7

Perception of self ..............................................................................................................................................7

Perception of work ...........................................................................................................................................8

Dancers’ Cultural Context and Perception of Health Care Providers ........................................................................8

Role models .....................................................................................................................................................8

Avoidance of mainstream health care ...............................................................................................................8

Movement Demands of Dance ...............................................................................................................................8

Posture and alignment ......................................................................................................................................9

Base of support .................................................................................................................................................9

Balance and proprioception .............................................................................................................................9

Movement Demands on the Spine, Pelvis, and Hip .................................................................................................9

Movement Demands on the Knee and Leg ..............................................................................................................9

Movement Demands on the Ankle and Foot............................................................................................................9

Shoes ...................................................................................................................................................................10

Training Oversights in the Traditional Dance Setting .............................................................................................10

The principle of periodization ........................................................................................................................10

The principle of specificity .............................................................................................................................10

The principle of overload training ...................................................................................................................11

The principle of overtraining...........................................................................................................................11

Summary ..............................................................................................................................................................11

STRATEGIES FOR EFFECTIVE INTERVENTION ..............................................................................................................11

Prevention ............................................................................................................................................................11

Best Practice .........................................................................................................................................................12

Screening and Injury Reporting .............................................................................................................................12

On-site Care .........................................................................................................................................................13

REFERENCES ...............................................................................................................................................................15

REVIEW QUESTIONS ....................................................................................................................................................23

Opinions expressed by the authors are their own and do not necessarily reflect the views of the Orthopaedic Section.

The publishers have made every effort to trace the copyright holders for borrowed material.If we have inadvertently overlooked any, we would be willing to correct the situation at the first opportunity.

© 2008, Orthopaedic Section, APTA, Inc.

Course content is not intended for use by participants outside the scope of their license or regulations. Subsequent use of management is physical therapy only when performed by a PT or a PTA in accordance with Association policies, posi-

tions, guidelines, standards, and ethical principals and standards.

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Epidemiology of Dance Injuries: Biopsychosocial Considerations in the Management of Dancer Health

Marijeanne Liederbach, PT, PhD, ATC, CSCSHarkness Center for Dance InjuriesNYU Hospital for Joint DiseasesNew York, NY

LEARNING OBJECTIVESUpon completion of this monograph, the reader will

be able to:1. Identify biopsychosocial factors influencing injury oc-

currence among dancers and implement strategies to modify risk and prevent injury.

2. Recognize the value and limits of the screening process for dancers and understand how to utilize screening in a broader model of prevention and intervention.

3. Evaluate ergonomic risk within the dance workplace and create strategies for acceptable and effective modification.

4. Choose appropriate therapeutic techniques aimed at efficiently and effectively restoring function and minimizing risk for reinjury.

INTRODUCTION

“Dance is an artist’s job, not an athlete’s job.”1 This quote by an unidentified ballet coach from the Royal Ballet captures a sentiment fundamental to the under-standing of why dance medicine has emerged as a sub-specialty to orthopaedic and sports medicine. Dancers and athletes share a common requirement for extensive physical training that leads to the acquisition of highly specific and refined motor skill. Unlike athletes, how-ever, dancers ultimately hone their physical prowess for the chief purpose of developing artistic expressivity, an ethereal quality without which a dancer’s physical virtu-osity is incomplete. Dancers are trained to perfect their physical skills not for the sake of winning competitions, earning prize money, or scoring goals, but for the purpose of conveying dramatic intent. The reason this distinction is important for the reader to appreciate is because danc-ers, to this day, adhere strongly to a cultural perspective of training that is based in artistic rather than scientific traditions. Their work environments, therefore, do not incorporate modern principles of conditioning, leaving dancers relatively unprepared for stresses encountered during their career.

In the early 1980s, recognizing that dancers and dance as an art form were in crisis because of rampant injury problems, health care professionals and dance profes-sionals interested in the health and well-being of danc-ers began to organize around the cause of health and safety promotion. Dance medicine formally emerged in the United States at that time when, for the first time, continuing medical education courses focusing on the unique health problems of dancers were offered by the Massachusetts General Children’s Hospital in Boston, the

Nicholas Institute for Sports Medicine and Athletic Trau-ma at Lenox Hill Hospital in New York, and the American Dance Festival at Connecticut College and Duke Univer-sity. Following these efforts, more organizations began to emerge and advance knowledge to the public about the special health needs of dancers and other perform-ing artists; these organizations included the Performing Arts Medical Association, the International Association for Dance Medicine and Science, the Harkness Center for Dance Injuries, the Miller Healthcare Institute for Performing Artists, the DanceUSA Taskforce on Dancer Health, the Performing Arts Special Interest Groups of the American Physical Therapy Association, and the Perform-ing Arts Work Group of the National Athletic Trainers As-sociation.

EPIDEMIOLOGY OF INJURIES IN DANCEEpidemiology is the study of disease frequency and

of factors associated with the distribution and determi-nants of disease.2 In a dance medicine context, epide-miology is the methodology by which one measures the number, nature, and cause of dance injuries in or-der to determine risk associated with dance activity.

RiskRisk is defined as the probability of an adverse out-

come,3 and all dance activity creates some degree of risk4 (Figure 1). To be effective at reducing health risks and injury incidence among dancers, it is essential to first know the magnitude and nature of the dance injury problem and to have information about when, where, how, and to whom the injury occurred5 (Figure 2).

RISK Probability of Injuries

MAGNITUDE OF PROBLEM

Uniform Injury Reporting

PREVENTION Decrease of Injury Incidence

Figure 1. Preventing injuries by reducing risk.

PrevalenceThe prevalence of dance injuries is reported to be

as high as 75% to 97%, suggesting that participation in dance activity is very risky.6–10 From a clinical point of view, however, prevalence values can be misleading with regard to actual activity risk because, while preva-lence studies shed some light on the number of injuries present in a sample of dancers at a given point in time, they do not give us information about how many new injuries occur to dancers over a discrete period of time nor do they yield prospective, exposure-controlled data about factors associated with the injury onset.

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Epidemiology: the study of distribution and determinants of dance injury

Descriptive Analytical

How many? To whom? Where? When? WhatOucome?

Why? How?

Occurrence- frequency- prevalence- incidence

Performer- biology

Participation- level

Participation- role/function

Anatomic

Geographic

Surface

Apparatus

Onset- traumatic- insidious

Chronometry- time of day- time of year- activity type

Severity- injury type- time lost- function lost- cost

Intrinsic- the person

Extrinsic- from without

Mechanism- inciting events

PREVENTION

Complicating matters, when reading the dance medi-cine literature one discovers that the definitions for injury have varied greatly and have included such methods as defining injury by dancer self-reports of subjective pain, by recall count of number of self-defined injuries over a career lifetime, and by retrospective chart reviews of medically documented impairments and disability reports. In this monograph, risk of dance activity will be compared with risk of sports activity from the point of view of prospective data using time lost from activity as the definition of in-jury, and the literature will be explored for high-level evi-dence about factors associated with risk for dance injury.

IncidenceBack in the 1970s, Dr. James Nicholas11 popularized an

idea that dance is as physically tough as football and as men-tally stressful as bullfighting. The aim of his expert opinion paper was to help sports medicine clinicians appreciate the different neuromuscular, environmental, and psychometric demands imposed on participants by various activities. By today’s standards of evidence,12 activities are now more objec-tively evaluated for risk using an injury rate equivalent scale, a 4-point classification system that evaluates the number of in-juries occurring to groups of performers over 1000 units of ex-posure to their activity. With this system, injuries are counted when they fit a definition of having resulted in at least 1 day of missed participation from the activity beyond the day of the injury event itself.13 Within the injury rate equivalent system, an activity is considered low risk if the number of time-lost injuries that occur per 1000 units of exposure is between 0 and 2. As the number of time-lost injuries per 1000 exposure units goes up, so too does the risk score. An activity that yields 2.1 to 4.0 time-lost injuries is considered low to moderate risk, compared to a moderate-risk to high-risk activity that would yield between 4.1 and 6.0 injuries per 1000 exposure, and a high-risk activity that would yield 6.1 or more injuries per 1000 exposures. Using this criteria, dance falls somewhere between

level 1 (low risk)14,15 and level 2 (low to moderate risk)16 for injury risk, well behind football, which qualifies as a level 4 (high risk) activity.13,17

Work-related Musculoskeletal DisordersWork-related musculoskeletal disorders are defined by the

United States Department of Labor as injuries or disorders of the muscles, nerves, tendons, joints, cartilage, and interverte-bral disks associated with exposure to risk factors in the work-place18 that result from repetitive tissue loading in combina-tion with other physical, nonphysical, and nonoccupational risk factors.19 It is generally agreed that 65% of all dance in-juries result from repetitive strain and 35% result from acute trauma,8,9,14,20–23 and that 95% to 98% are successfully treated with conservative care while 2% to 5% will require surgical intervention.8

Injury Distribution by Anatomic RegionInjuries in dance are similar to injuries in sports in the

sense that they are activity specific, emerging in patterns representative of the motion demands associated with the activity.6,24 Dance injuries occur most commonly in the lower extremities,8,16,21,22,25 especially to the foot and ankle region. Table 1 illustrates injury distribution by anatomic region as reported by different investigators. The foot and ankle region consistently emerged as the most common region of injury in every study. A different study16 that observed 4 distinct groups of dancers pro-spectively over a 5-year period for distribution of injury found similar results (Figure 3). In that study, foot and ankle injuries again emerged as the most common site of injury for each dance group. In Table 1 and in Figure 3, it can be further observed that relative to all injuries, bal-let dancers reported injuries to the foot and ankle more often than do modern dancers, whereas modern dancers reported a higher incidence of injuries to the spine, hips, upper extremities, and knees than did ballet dancers.

Figure 2. Components of a robust injury-reporting system. Reprinted with permission from Epidemiology of Sports Injuries.189 Copyright 1996, Dennis J. Caine.

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Injury Distribution by Other FactorsSex

No difference in injury frequency between men and women has been reported in the dance literature, but no-table differences have been reported with regard to types of injuries by sex. For example, injuries to the foot and ankle have been reported to occur more often among women dancers compared to men dancers.8,14,22,23 Men, on the other hand, have been reported to have a higher incidence of shoulder and back injuries compared with their women counterparts.8,22

Age and SkillWhen looking at injuries according to age and company

rank, one study conducted on elite ballet dancers found that 21-year-olds to 25-year-olds had more injuries than both 17-year old to 20-year-old dancers and 26-year-old to 35-year-old dancers.26 That same study reported that danc-

Author Leveland Style

Number ofInjuries

Distribution Injury Site

Quirk198425

Mixed levelBallet

2113 42.4%17.3%8.6%8.5%7.5%

foot and anklekneehiplow backleg

Liederbach198522

Professional levelBallet

256 48.8%18.4%14.5%7.4%7.0%3.9%

foot and ankleleglow backkneehipupper extremity

Solomon and Micheli 1986205

Professional levelModern dance

229 26.6%20.1%15.3%14.5%11.3%7.0%

foot and anklekneelow backupper extremityhipleg

Garrick and Requa199321

Professional levelBallet

309 37.2%23.0%6.8%

foot and anklelow backknee

Liederbach et al200816

Professional levelBallet

117 57%12%9%6%3%

foot and anklespinehip kneeupper extremity

Liederbach et al200816

Mixed levelModern dance

175 47%16%11%8%8%

foot and anklespinehip knee upper extremity

*Reprinted with permission from Liederbach M.48 Copyright 2000, J Michael Ryan Publishers.

Table 1. Distribution of Dance Injuries by Anatomic Location*

Figure 3. Percent of time-lost injuries by anatomic region over 5 years among elite ballet and modern dancers.

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ers in the corps de ballet rank had more injuries than ap-prentices, soloists, and principal dancers.26 Several studies have reported that injuries occurred more often among less-er skilled dancers when compared with elite dancers,14,15,27 and 2 studies have reported that injuries happen most often among adolescent dancers.28,29 One study found that injury severity among elite ballet dancers was positively correlated with increasing age and that incidence of stress fracture was highest among dancers who entered the profession at a later age.10

ExposureKadel et al30 and Liederbach et al31 both found that expo-

sure time among injured dancers was significantly higher than among uninjured dancers. Hamilton et al10 found that frequen-cy of injuries and time disabled were functions of exposure.

Personal factorsThree studies have reported that approximately 10% of

individual dancers in the group of dancers studied were more prone to injuries than all of the other dancers in that same group for reasons unrelated to age, skill, company rank, or exposure.8,15,21

When do injuries happen?Four studies in the dance literature have reported that

injuries occurred more often during performance seasons when dancers were engaged in work-related physical activ-ity for approximately 4 more hours per day when compared with other times of the year, such as during rehearsal and layoff periods.8,16,21,32 Three studies found the greatest inci-dence of injuries occurred during rehearsal periods when new work was being learned and participation in repeti-tive activity was at its highest.15,23,33 In the sports medicine literature, Hootman et al34 evaluated 182,000 injury reports from 17 different men’s and women’s sports over a 5-year period and found that the vast majority of sports injuries oc-curred during games in the competitive season versus dur-ing practice in the preseason or postseason periods, with the exception of gymnastics. Gymnasts, by contrast, got injured 3 times more often during the preseason practice phases than during competition seasons due to either a relatively decreased status of physical conditioning or to fatigue from increased training intensity and duration associated with practice schedules.17

Time Lost From InjuriesIn professional ballet, 90% of lost days are due to foot

and ankle injuries,9 and ankle sprain injuries are the sec-ond most common reason for most days lost from work in dancers in general.35 The number of days lost from work because of injury ranges from 7 to 28 among professional dancers,9,14,15,22 whereas 82% of students injured in ballet class had an average length of disability of 54 days.27

Cost of InjuriesThe human and economic costs of injuries are great. In

health care outlay costs, average out-of-pocket expenses

have been estimated to be between $1300 and $3000 per minor injury and in excess of $10,000 per major injury.8,21

ETIOLOGYTo date, attempts to understand the root causes of

dance injuries have largely concentrated on the physi-cal aspects of dance as an activity and on the physical vulnerabilities of dancers as participants. But even when physical deficiencies are established prior to participa-tion, their correspondence with later injury is very low.36,37 Relatively few studies in dance have examined the influ-ence of environmental and psychosocial risk factors on injury occurrence. It may be that dancers’ psychological attributes and social influences play a significant role in the occurrence of injury and on the progression and out-come of work-related musculoskeletal disorders. Studies from other areas in medicine have shown that psycho-social factors are at least as important, and often more important, than physical factors in determining health.38 The purpose of this monograph is to consider the health of dancers from a biopsychosocial perspective.

CauseUnderstanding the cause of injury is central to advanc-

ing knowledge, particularly regarding prediction and pre-vention.39 Dance injuries result from a complex interplay between human (intrinsic) risk factors and environment (ex-trinsic) risk factors (Figure 4).39–45 Risk factors are defined as those entities that contribute to the cause of injury. They need not be, and often are not, direct causes of in-jury; instead, they are markers for particular conditions, which, by virtue of association with other determinants

INJURY

Intrinsic Variables

Extrinsic Variables

Figure 4. Injuries result from a complex interplay between intrinsic and extrinsic variables.

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tor of stress by whom the amount of strain evoked by participation in the activity can be altered, thereby in-fluencing the capacity to perform in various situations, and also influencing the risk to sustain an injury.”45

Risk Factors in DanceAs noted in the opening paragraph of this monograph,

dance training is dictated by artistic traditions, not scien-tific principles. As such, traditional dance training does not universally incorporate modern conditioning methodolo-gies that might better prepare dancers for the metabolic and tissue-specific stresses and strains they encounter during rehearsal and performance.47 Factors associated with the etiology of common dance injuries can be condensed into 3 broad categories: occupational demands, movement de-mands, and training oversights.48

Occupational Demands of DanceDancers, like other athletes, are subjected to circum-

stances that require above average strength, flexibility, coor-dination, and concentration. Further, they are often subject-ed to rigorous aesthetic demands, such as the maintenance of thinness and the need for exquisite motor control at end-range postures on precarious bases of support. Added to these occupational demands, there is little professional or financial security available to those pursuing a career in

Figure 5. Stress-strain-capacity model of injury cause modified for dance. Reprinted with permission from Sports Medicine.45 Copyright 1992, Wolter Kluwer Health.

Dancer (Intrinsic) Examples of Physical Factors Examples of Psychosocial Factors Body composition Motivation level Fitness level Self efficacy and esteem Prior injury Locus of control Menstrual status, hunger, thirst, fatigue Personality: risk-taking attitude

Dancer

Dancer’s Environment (Extrinsic) Workplace Conditions Nature of Work Ambient temperature, light, noise Exposure Costumes, shoes, set design, surface Effort

INJURY Situational Factors

Psychosocial stressors: attention Emotional state: mood Coping resources: support Social: adjust to new policy

of the same condition, may be confounded as a causal factor.39,46 Risk factors should be seen as hypotheses until they have been substantiated as defensible injury predic-tors through correlational or experimental research.39,45

Intrinsic factors that can influence injury occur-rence include: age, sex, general and mental health, pri-or injury history, fitness level, body mass index, body alignment, morphology, limb dominance, muscular flexibility, joint range of motion, joint laxity, muscu-lar strength, muscular balance, and muscular reaction time. Environmental factors in the dance workplace to which dancers are exposed that potentially impact health include: floor construction and incline, ambi-ent temperature, noise and light, live music tempo, costume and set design, level of performance, level of skill, preparation of the facility to handle emergen-cies, employer policies regarding breaks, hydration, stretching, time-loss discipline, conditioning practices and body weight regulations, and shoe type and shoe-surface interface. Situational variables also come into play in the form of workplace attitudes, peer pressure, and support structures, as illustrated by a stress-strain-capacity model (Figure 5).40,45 The stress-strain-capac-ity model considers athlete behavior along with other intrinsic and environmental factors in injury occur-rence. It views the participant as “an active manipula-

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dance, often making access to health care difficult. Many dancers have little or no health insurance.49,50 Only 11% of dance groups in New York City provide health coverage for their dancers, and only 21% carry workers’ compensation insurance.51 These conditions, plus the fact that dance, un-like sports, knows no regular seasons, place a tremendous psychological burden on the performer.6

Selection of DancersDancers are typically selected for artistically pleasing

qualities manifested, in part, by certain physical and psy-chological tendencies. Elite dancers, similar to elite ath-letes, represent the top of a broad-based field of competitive students27,52 who have survived an inherent selectivity for the body type and personality able to adapt well to the aes-thetic, psychological, and physical training stresses along the way. The selection of dancers is highly subjective, based not on measures of time or distance but on emotional and aesthetic attributes,53–56 and tends to be intensely discrimi-nating. In national ballet schools, only 5% of the children who begin their training at the age of 8 graduate 9 years later.57 Of approximately 20,000 dance students audition-ing annually for company-affiliated schools, only 10% will be chosen for the school, with only 0.1% making it to the stage.52 Data from profiling studies do indeed indicate a typical somatotype. In general, the typical dance archetype is described by low body weight and fat, long and slender legs, high-arched feet, and a general predisposition for ar-ticular and muscular flexibility.27,58 Forty-eight elite women dance students (average 14.9 years of age) were followed at the School of American Ballet to distinguish the physi-cal and mental factors associated with dropping out of the profession. Over the 4 years they were watched, 55% of students in the study sample stopped dancing. Those who dropped out had more eating problems, injuries, and defi-cits on orthopaedic examination. The girls who were not genetically thin appeared to be most vulnerable to eating disorders.27

Like elite athletics, among whom discriminate analy-ses separate somatotypes by sport played,59 a homogenous morphology is evident at the level of the professional danc-er. Some have speculated that dancers who make it to the elite level do so by virtue of a Darwin-like “survival of the fittest” mechanism, such that their particular set of anatomic attributes27,60 allows them to perform successfully without experiencing debilitating injury.53,61

Physical TendenciesMobility

Dancers tend to be hypermobile and selectively hyper-flexible.20,58,60,62–64 While these are aesthetic assets in that they permit the accomplishment of the extreme ranges of motion needed in many styles of dance, these attributes may increase the risk for injury. Chronically overstretched muscles and tendons show decrements in the muscle spin-dle output and reflex force characteristics.65–67 In addition, hypermobile dancers perform poorly on tests of proprio-ception,68 suggesting that changes in neural elements ac-

company the changes in tissue length, which may adversely affect motor skills.69 Anterior cruciate ligament injuries, for example, have been linked to altered muscle recruitment patterns associated with a long amortization phase in the stretch reflex response.70,71

Selective muscle tightness and weaknessScreening data from tests performed at the Harkness

Center for Dance Injuries on 800 healthy, uninjured adult advanced (college or professional) dancers from various dance forms revealed that 76% tested positive for calf tight-ness and 63% tested positive on Thomas tests for hip flexor tightness. In that same population of dancers, 68% failed tests for normal muscular endurance of the plantarflexors; 50% failed tests for functional quadriceps control (main-tenance of lower extremity alignment during bench step-ping); and 38% failed supine double-leg lowering tests for abdominal strength and trunk stability. Past studies corrobo-rate the finding that dancers lack strength in certain muscle groups.58,72–75 Dance is an intense, highly repetitive, high-impact activity. Muscular strength and endurance are im-portant in joint and postural stability, shock absorption, mo-tor control, and performance stamina. Relative imbalances and deficits in strength pose significant risks for injury.

Thinness and low energy expenditureIn the sports medicine literature, dance is considered

a “thinness sport,”76 and women ballet and modern danc-ers tend to be, on average, only 75% and 88% of expected body weight, respectively.77,78 The most technically talented dancer may not be accepted into a ballet company because of body size.77 Aberrant nutritional patterns in dancers are associated with stress fractures before the development of bone density changes, suggesting that the quality of bone may be affected before clinical changes are seen.36 Malnu-trition is suspected to be common among dancers because dance is not a calorie-expensive movement activity.25,26 As a result, chronic dieting to restrict calorie consumption as a strategy for maintaining low body weight is common among dancers.77–86 Inadequate energy intake and nutritional im-balance are factors known to increase injury and illness risk. The actual risk for injuries associated with the female athlete triad syndrome76,87,88 (the relationship between amenorrhea, disordered eating, and osteoporosis) is difficult to quantify,87 but clinicians should be aware that amenorrhea has been linked to decreased estrogen, a condition that is linked to the pathogenesis of osteoporosis.20,81,89

Menstrual abnormalities are well-documented among dancers and may be related, at least in part, to nutrition-al deprivation. Among dancers, there is little knowledge about basic principles of nutrition and there is a high degree of food faddism.89 There is a moderate incidence of anorex-ia nervosa and bulimia among dancers,81,83 but there is far more disordered eating, a phrase coined by the Women’s Task Force of the American College of Sports Medicine76 to describe chronic restrictive and sometimes ritualistic, compulsive eating patterns. This is a condition the physical therapist should be aware of because of its potential effect

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on the dancer’s ability to fully recover from injury. Danc-ers have reported regularly consuming as little as 1000 to 1800 kilocalories per day, in some cases since the age of 12, despite age-related or growth factor demands of physi-cal development and despite several hours of dancing per day.77,85,89,90

One important factor for the clinician to understand from the discussion is that dancers are often driven more by how they look than by how they are functioning during performance. Some dancers have an extreme fear of fat and they may under-eat or become exercise dependent to con-trol their weight,31 a situation that can cascade into central fatigue, muscle failure, and injury.

Psychological TendenciesPsychosocial factors in dance are complex and can

contribute to occurrence, progression, and outcome of in-juries.91–94 The biopsychosocial model was first described by Engel95 in 1977, with the purpose of looking beyond mind and body factors to also include the role of society on illness behaviors. Engel95 concluded that any injury must be viewed from a multidimensional perspective that takes into consideration not only biological factors, but also psychological and social factors, since physical inju-ries are interpreted cognitively and perceived emotional-ly. Waddell38 later theorized that the cognitive belief one has of an injury in turn impacts mood and pain behavior, making the perception of symptoms variable. One danc-er may experience an injury as more or less severe than another dancer with the exact same injury according to the belief held about the injury and the emotional mean-ing associated with that belief.

PersonalityPersonality traits associated with the drive necessary

to achieve elite levels of physical skill in ballet have also been associated with the occurrence of injuries. Bal-let dancers with the greatest number of total injuries throughout their careers, regardless of sex, were found to be significantly more enterprising than those with fewer injuries, and ballet dancers with stress fractures and other overuse injuries were those with the personality type of overachiever.10

Perception of selfPersonality type alone, however, can rarely predict

who will potentially become injured.38 A state of psy-chological distress, for example, can influence injury outcome. Theories given to explain the relationship be-tween stressful life events and injuries include attention disruption of the cognitive level96 and increased muscular tension and reduced motor coordination on the somatic level.97

Negative affective states, such as depression and anxiety, have been shown to be important components of work-related injury etiology.38 Patterson et al92 stud-ied 46 professional ballet dancers prospectively over an 8-month period to determine injury vulnerability factors

of a psychosocial nature. They measured positive and negative stressful life events within the context of in-dividual perceptions of social support (defined as “the subjective belief that there exist sources of support, help, and caring within one’s social network”) and found that recently experienced stressful life events were unrelated to injuries for all the dancers, but that negative life events were significant predictors of subsequent injuries for those dancers who reported low levels of social support.

Performance anxiety, or stage fright, has also been associated with injury in dancers. Performance anxiety, reported to occur in more than 40% of dancers,98 is de-fined as an internal conflict between one’s need to pub-licly display his or her artistry coexistent with an often profound fear of proving inadequate and suffering public humiliation and rejection.99 As a cognitive event, per-formance anxiety is accompanied by somatic responses, including elevated cardiovascular and neuroendocrine activity.100 Smith et al101,102 measured trait anxiety in dancers in relation to injury and found that 61% of 46 professional ballet dancer injuries were predicted by a combination of cognitive and somatic anxiety subindica-tors, including heightened physical arousal, loss of focus, and worrying.

Other-oriented perfectionism is a common theme among professional dancers,103 as is self-surveillance. The dancer’s sense of self is primarily formed as a result of the perception of how others see the dancer, wherein the dancer develops a role identity instead of a self-iden-tity.104 In a review of 500 injury reports submitted by 644 dancers over a 2-year period, subjective reports of fatigue, body dissatisfaction, drive for thinness, bulimic tendencies, and perfectionism were significantly higher among injured dancers compared with uninjured danc-ers.105 Adam et al106 found that absenteeism in dance was related to stress and negative mood state such as depres-sion, fatigue, confusion, and anger.

Dance training stimulates the externalization of goals, which can lead to self-destructive behaviors by placing emphasis on achievement of superior ability, daily per-sonal best, fear of failure, inability to accept personal mistakes, and unrelenting threats to self-esteem. A con-sistent emphasis on a performance-oriented climate in dance with constant body judgment has been associated with development of maladaptive dispositions in many young dancers.104 The external reality of the profession had an adverse influence on dancers’ relationship with self and their future-directedness such that 43% of danc-ers surveyed in a university dance program had symp-toms of depression. These dancers expressed frequent feelings of hopelessness and uncertainty about their fu-ture, doubts about success, lack of time in life to accom-plish what they want, and being unlucky. While there was no statistical relationship in that study between num-ber of hours training per day and overall mood state, the students dancing more hours per day were measurably more sad. Among those students, lack of social support and feelings of loneliness resulted in a longer period of

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recovery following injury. This finding corroborates work by Mainwaring et al,94 who found a strong correlation between psychological stress and injury duration.

Perception of workThere is much evidence to indicate that workplace

stress has a great influence on health.7,94 Since inju-ries in dance occur at work, or are believed to be the result of work, the cognitive, affective, behavioral, and social elements of those injuries are inextricably related to the workplace. Byhring and Bo9 found that 61% of dancers believed that factors related to training (eg, in-sufficient preparation before rehearsal and performance periods) caused their injuries. In addition, the authors found dancers felt their daily ballet technique class did not prepare them for the modern dance repertoire they were subsequently exposed to in rehearsal and they felt that injuries would occur less often if they were better prepared mentally and physically for their work. Among those same dancers, 78% experienced negative stress at work on a regular basis and 64% felt they had no influ-ence on decisions about their working conditions. van Mechelen45 reminds us that injury risk factors include ap-preciation of the participant’s attitude about risk and sub-sequent risk-taking behavior as well as the participant’s perception about ability for, and barriers to, success.

Dancers’ Cultural Context and Perception of Health Care ProvidersRole models

Ninety-three percent of dance teachers became teachers because of injury.107 Furthermore, most dance injuries among dance teachers go untreated because the teachers report being too busy to go to the doctor or be-ing unable to go because of lack of insurance or ability to afford the visit.107 Many successful teachers in dance are persons who survived the rigors of dance without disabling injury and who, thus, believe that their way of training is superior (eg, “tough it out;” “dance through the pain and leave your troubles at the studio door”). In addition, many dancers of a generation ago who sought medical care for injuries, before concepts of relative rest were common, were given the then-gold standard advice to stop dancing, which was an unacceptable option to them. While this was appropriate medical advice for the times, a directive such as this only made dancers more leery of medical advice altogether; thus, that generation of dancers, proud about having accomplished a career without stopping for pain and without the benefits of sports medicine services, believe that doctors don’t un-derstand them and that their way of managing aches and pains is superlative to all others.108

Avoidance of mainstream health careOn top of the ubiquitous insurance barriers, dancers

avoid contact with health care professionals for other rea-sons. For some, there is a strong feeling that they are not understood by doctors.109 As described by Krasnow and

associates6: “A dancer is someone who trains daily for 10 years or more, investing time, money and energy with the foreknowledge that gainful employment is question-able, and that even success guarantees little, in fact a good chance of living at the poverty level. Dancers have differ-ent values and priorities from persons in mainstream career cultures.”(p8) In the same study, the authors reported that only 20% of injured dancers pursued a physician visit for care of their injuries, citing reasons such as lack of money, lack of time, and a feeling that the physicians would view their problems as more incidental than they actually were.

An understanding of the psychosocial culture within which professional dancers rise is crucial to working with them successfully in a health care context. The voca-tional calling to dance is so overwhelming that a dancer’s body becomes her identity;1 because of this, injury is ex-perienced as a profound crisis for the dancer. Quoting Hamilton110(p25): “As with any professional athlete who depends on the maintenance of the body, the dancer be-comes very conscious of injury. Like the racehorse, the dancer’s life depends entirely on their physical condition, so psychologically they display great insecurity with regard to aches and pains. Every affliction, no matter how minor, becomes a catastrophic accident with thoughts of ‘what if I can’t dance’ flashing through their minds.” Clinicians may, thus, view the dancer as obsessive and unreasonable.

Macchi and Crossman111 found that more than half of dancers who saw physicians felt the doctors were imper-sonal and did not give them information about their in-juries. As a result, the dancers did not comply with the medical advice given. Scialom et al23 also found that 80% of dancers did not comply with recommended health behavior changes in their work or lifestyle habits, even though 83% of them had resolved past injury problems after seeking help from a health care practitioner. Scia-lom et al23 reported that, although dancers investigated the cause of injury with a health care professional, they them-selves could not later explain its occurrence or any details about the medical evaluation. Furthermore, those same dancers were willing to change their exposure to dance for the short term to pursue medical treatment, but they were not willing to change their technique or training habits or strategies in the long term, even if a physician spent a lot of time educating them as to reasons for such adaptations during their clinical visits. The treating physicians felt they were communicating very clearly with dancers and their teachers about specific diagnoses and treatments, where-as the dancers felt they were not asked anything specific about their work.23

Movement Demands of DanceHamilton has noted that even dancers who are perfect-

ly conditioned, technically well-trained, and psychologi-cally prepared for the rigors of a life in dance will experi-ence injuries, simply due to the nature of the movement demands.110 For example, each day in class dancers will perform approximately 200 jumps, some of which impose forces as high as 12 times body weight on the performer.112

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Each full relevé (heel rise) a dancer does onto the tips of the toes loads the ankle and first metatarsophalangeal joints with forces equivalent to 10 to 12 times body weight.113

Of course, not all dancers are equally prepared for stresses associated with the dance workplace and, thus, enter the activity with variable levels of neuromuscular condition-ing and joint structures that will influence the arthrokine-matics of their training.114 Pathomechanics is the study of the origin of injury, a discipline within which one attempts to explain how and why a particular injury occurs. Knowl-edge of pathomechanics is important for the dance medi-cine physical therapist to effectively manage and prevent injuries. Some movement demands in dance suspected to be associated with injury are reviewed below.

Posture and alignmentIn classical ballet, there are 5 basic stance postures,

known as 1st through 5th position, from which all move-ment tasks are executed. In these stance positions as well as during all leg gesture and movement tasks, maximal ex-ternal rotation of the lower extremities, known among the dancers as “turnout,” is expected at all times except during unusual choreographic applications. The amount of turn-out considered ideal is 90° per limb. Since femoral neck anteversion angles in dancers are similar to age-matched, non-dance trained individuals in the general popula-tion,115 dancers must borrow movement from the spine, pelvis, and lower extremity segments to achieve turnout in stance.58,116 It is theorized that dancers friction-couple their feet with the floor to achieve full turnout, a behavior that may produce joint motion and muscle imbalance from plastic changes to tissues surrounding various joints.117–120

Base of supportThe feet do not always serve as the body’s base of sup-

port in dance.47,48 Many dance forms rely on the knees, buttocks, spine, neck, upper extremities, or head to serve as a transitory base of support, presenting a whole new class of injury risks.47 Dancers are sometimes asked to try one of these interesting postures without any special instructions, safety precautions, preconditioning exercises, or warm-up activity and then often repeat the maneuver over and over again.

Balance and proprioceptionDuring preparticipation screenings held at the Hark-

ness Center for Dance Injuries, 40% of dancers routinely fail the Romberg static balance tests. Dancers rely on a keen sense of balance to sustain extremely small bases of support for extended periods of time, as well as to move rapidly and expansively between spatial postures, often shifting direction, timing, and level multiple times within just 1 movement phrase. Balance is governed by postural control systems, including: (1) the vestibular apparatus, which provides information about body accelerations and orientation in an inertial frame of reference; (2) the visual system, which provides information about the environment and about the orientation and movement of the body; and

(3) the proprioceptive system (muscle, joint, and cutane-ous receptors), which provides information about the state of the effector system and the environment.121 Balance deficits place the dancer at increased risk for trauma be-cause of the associated alterations in neuromuscular feed-back.122–126

Movement Demands on the Spine, Pelvis, and HipThe majority of back injuries, like most other dance in-

juries, can be attributed to repetitive movement stress. In dance, repetitive microtraumas occur from asymmetrical loading of articular and soft tissue structures during end-range movements that level and unlevel the pelvis as the center of gravity is shifting.127 Sacroiliac dysfunction is the most common lumbosacral pathology in professional classical dancers and is a result of the forces inherent in the extreme movement demands and the ligamentous laxity possessed by most elite dancers.128 The aesthetic nature of classical dance requires the trunk to be stable during large movements of the lower limbs, which may result in functional hypermobility of the pelvis. Many dancers are able to assume extreme hip and lumbar spine hyperextensions, creating a great deal of spinal rotation in opposition to the stance limb. The attempt to accom-modate these ranges of motion may lead to excessive ver-tebral rotation, hypermobility at the lumbosacral and sac-roiliac joints, or sometimes spondylolysis. The incidence of spondylolysis and spondylolisthesis in dancers (12% to 17%) resembles that of elite gymnasts and is higher than the general population (6%).20,129

Lower extremity muscle imbalance is considered both a cause and an effect of lumbar spine and pelvic injury.130,131 Dancers frequently complain of clicks, pops, and snaps around the hip, which are most often associat-ed with a tight iliotibial band,132 as well as long and weak iliopsoas accompanied by weak gluteal muscles.133,134 Intra-articular causes of snapping hip symptoms include synovial chondromatosis, loose bodies, osteochondritis dissecans, osteocartilaginous exostosis, labral tear, or in-verted labrum.135–138 A full monograph has been devoted to the topic of hip injuries in dance.

Movement Demands on the Knee and LegThe knee is exposed to considerable stress in dance.

Dancers perform approximately 200 jumps per class, usually with some transverse plane rotation for the lower limb provided by the tibiofemoral joint.139 Patellofemoral syndromes are common in dance and are thought to be related to the high frequency of eccentric loading sec-ondary to the repetitive landings from jumps.140–144 A full monograph has been devoted to the topic of knee inju-ries in dance.

Movement Demands on the Ankle and FootA full monograph has been devoted to the topic of

foot and ankle injuries in dance, but a few key issues will be discussed here. Two of the regularly practiced ankle movements in dance, relevé and plié, are associated with

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a number of orthopaedic problems. During relevé en pointe, the dancer rises to the tips of her metatarsal pha-langes, bearing full body weight there while performing movement tasks. Forces at the foot and ankle are estimat-ed to be 10 to 12 times body weight, comparable to that of a runner doing a 6-minute mile.113

In the position of relevé, the dancer experiences less anatomic stability at the talocrural joint, resulting in in-creased activity of the peroneal muscles.145,146 Further, winging, or relevé with eversion (a stylistic embellishment on the formal relevé position), is a behavior commonly practiced by dancers that markedly increases the pres-sure at the first metatarsophalangeal joint. This elective foot posture also places the first ray in a mechanical dis-advantage, requiring the flexor hallucis longus and oth-er supporting soft tissues to overcome inordinate tensile forces and encounter greater resistance to flexion of the digits.147 If the flexor hallucis longus tendon (referred to as the dancer’s Achilles heel)145 becomes inflamed, it may progress to partial rupture. Erosion of this tendon within its osseofibrous tunnel (known as stenosing tenosynovitis) can result in a condition commonly referred to as trigger toe.118,141,145,148,149

Dancers spend a substantial portion of their work time in relevé, which often results in a short and strong gastroc-nemius-soleus complex and accompanying loss of active dorsiflexion.58,73,150 As a result of this training adaptation, functional equinus is common. The pathomechanics un-derlying equinus include adaptation for dorsiflexion at the midtarsal joint region, thereby extending pronation and ex-posing the dancer to excessive pressure and tensile forces on the medial column of the foot. This motor behavior can lead to increased compression forces at the lateral cuboid, since prolonged pronation allows for an unlocked forefoot near the toe-off phase of gait where the angles of pull of the anterior tibialis and peroneal longus muscles are less optimal in their relationship to the first ray, thereby pre-venting the ray from assuming its most effective position as a stable and rigid lever for propulsion.151,152

Related to the position of plié, men dancers have been shown to develop anterior ankle impingement problems more frequently than women dancers. Its occurrence has been associated with years of high-impact landing from large jumps into the demi-plié position where anterior ar-ticular margins of the tibia impinge on the talus and bone spurs develop. Anterior ankle impingement is also associ-ated with eccentric weakness of the calf.142 Ballet dancers, when compared with soccer and football players, have been found to possess similar levels of calf strength but significantly weaker dorsiflexors both alone and in relation to the plantarflexors and overall ankle strength.153

ShoesUnlike athletes who wear shoes specially designed to

absorb shock and stabilize foot and ankle joints, danc-ers wear only thin slippers, toe shoes, flat-soled leather shoes, or no shoe at all. The emphasis of classical dance footwear is on style and tradition. Traditional dance disci-

plines employ shoes that have undergone little or no modifi-cation for generations despite the vastly improved materials available.116 Indeed, the major construction materials of the ballet toe shoe are burlap, wheat paste, satin, cardboard, hard rubber, and leather.118 Albers et al154 found that pointe shoes, compared with barefooted walking, increased peak plantar pressure in dancers when doing functional move-ment due to a reduction in the amount of plantar surface contact area they could establish with the ground. The au-thors concluded that ballet shoes provide some stability but no absorption or attenuation of ground reaction forces.

Training Oversights in the Traditional Dance SettingPerhaps the most important category of etiologic factors

associated with dance injuries is training oversights. Four of the major principles of kinesiological science155 are neglect-ed or poorly incorporated into dance settings. Because they are so important to the prevention of dance injury, each will be addressed separately. These principles are: periodiza-tion, specificity, overload training, and overtraining.

The principle of periodizationThe principle of periodization is concerned with the

timing and intensity of training exposures. This principle asserts that sufficient time must be allowed between work-outs for tissue growth, nutritional replenishment, and bio-chemical resynthesis to occur, while exposures to work overloads are gradually increased in order that optimal physiological development and fitness be achieved.155 One problem inherent in traditional dance settings is that regulated periodization of training and performance ex-posures is lacking. Typically, dance company schedules are not as seasonally predictable as organized sports schedules. Hence, adequate rest cycles and safe, step-up phasing of performance stress overloads are not reliably incorporated, thus placing the dancer at increased risk for repetitive stress and fatigue injuries.

The greatest number of injuries per year are reported during the end of the day and the end of performance seasons when dancers became most vulnerable to fa-tigue.30,156,157 Fatigue has been demonstrated to have ad-verse effects on neuromuscular control, coordination, reflex activity, and muscular power.65,158–160 Previous re-ports161–163 have implicated muscle fatigue as the origin of tibial stress fractures. Stress fractures are a common injury in ballet dancers.164,165

The principle of specificityThe principle of specificity refers to the phenomenon

wherein a specific demand made on the body results in a specific response by the body.155 The principle states that in order for a particular movement skill to be achieved, that skill must be trained by imposition of exactly simi-lar motions, intensities, and durations to that of the goal movement.166 For example, if a dancer wants to become proficient at a particular type of jump, she should prac-tice that jump in a constructive, progressive, and exacting manner until the ultimate level is achieved.

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Traditional dance settings typically lack specificity when it comes to crossover of movement vocabulary from the technique classroom to the choreographic application in the rehearsal and performance setting, as well as in met-abolic pathway training in classroom versus stage perfor-mance.32,72,79,167–169 Motor patterns, muscular contraction demands, and cardiopulmonary demands vary between the classroom and stage.167,168,170 Classroom technique training remains relatively constant while the choreographic appli-cation is ever-evolving in its creative departure from base-line technique. An unspoken and ungrounded assumption that dancers are ready to handle these differences permeates most dance environments, again leaving the dancer vulner-able to otherwise avoidable injuries. For example, dance training in the classroom does not specifically precondi-tion for the demands of lifting; hence, the dancers who are required to execute lifts are at risk for traumatic overload injuries. In 3 British ballet companies, one third of all back injuries suffered by the men were attributed to the demands of lifting.171

The principle of overload trainingThe overload principle states: “Beneficial human perfor-

mance adaptations occur in response to demands applied to the body at levels beyond a certain threshold value, but within the limits of tolerance and safety.”155(p259) The limits of tolerance and safety are often exceeded in dance, par-ticularly when a student increases from 3 to 5 classes per week during the school year to 3 to 5 classes per day in a summer-intensive program. Another example where the limits of tolerance and safety are violated would be similar to the situation described above under specificity, where the shift from classroom movement to studio or stage move-ment is progressed without proper overload step-up training for safe mechanical and physiological management of the performance stresses. If too great a stress is imposed over a very short time period, the body will be unable to adapt and there will be a decrement in performance, possibly resulting in injury.

Thought of from the opposite side of the same coin, the overload principle also asserts: “Low-level demands, to which the body has already adapted, are not sufficient to induce a further training adaptation.”155 Once a dancer has reached an advanced level of technique, the demands of the classroom training remain relatively steady, failing to further advance fitness beyond the tasks of the classroom itself. While the repeated practice of technique during class work is very beneficial to both motor learning and motor control, it is inadequate training for the physiologic capaci-ties of strength, power, and endurance required by the more demanding aspects of performance.

The principle of overtrainingThe overtraining principle states that an individual ceas-

es to adapt positively to training stress when it is imposed in a sustained, long-term, and highly intense manner. Dancers are at risk for developing overtraining syndrome. Overtrain-ing syndrome is defined as an unexpected drop in perfor-

mance that cannot be attributed to illness or injury. This condition is most likely to occur when they are required to execute frequent performances, when they undertake con-sistent training that is monotonous and lacks sufficient rest periods, when they consume a poor diet, and when they are exposed regularly to psychosocial stressors including work or school conflicts. Poor coping abilities can exacerbate the problem.6,32,172–176

The lack of proper rest cycling and formal periodization to load build-up, as well as the lack of cardiovascular en-durance training inherent in dance training, its anaerobic nature, and the common practice of chronic calorie restric-tion for maintenance of low body weight, places the dancer at an increased risk for fatigue injuries.47 The adverse effects of fatigue on neuromuscular and psychometric performance are well-known,177–182 and fatigue has been associated with injury in several dance studies.16,30,32,105

SummaryConsidered together, the principles of periodization,

specificity, overload training, and overtraining characterize exposure to dance, in which a spectrum of effects come together in a correlative, dose-response relationship.183 In-jury risk relative to the dose-response curve varies for each person given the same exposure.184 In a defined group of dancers, measuring the number of injuries that occur rela-tive to exposure is the best way to determine if the injuries are related to the general activity risk of dance per unit time or to other factors such as unique intrinsic attributes of a given dancer or to particular features in the environment. It is for these reasons that a standardized measure of exposure is so important in an overall sequence-of-prevention strat-egy, which will be discussed next.

STRATEGIES FOR EFFECTIVE INTERVENTIONPrevention

Injury is something that every dancer seeks to avoid, and prevention is an element of health provision that is not only ideal from the point of view of the dancer and the health care provider, but also from the young dancer’s family and the dance organization as the preferred and most cost-effec-tive method of providing health care.185 The most basic ex-pression of risk is incidence, and the most basic expression of prevention is a decrease in incidence. Indeed, primary prevention is defined as a reduction of injury incidence.186 Measures of incidence alone, however, cannot reveal much about an individual dancer’s chance for injury.

Being precise about which individuals in a group are at particular risk of injury at any given time is extremely dif-ficult.187–189 In an article by Chmelar, Kevin McKenzie, the Artistic Director of the American Ballet Theatre, so wisely observed: “Some dancers are ‘workhorses’ while others are ‘racehorses.’ The former have an inherent ability to with-stand great stresses and repeated performances, while the latter are able to perform spectacularly but need more rest between periods of elevated physical stress.”190(p134) Diffi-culty with prediction, and thus prevention, arises because, as discussed in the sections above, dance injuries result

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from a complex interaction between many different intrin-sic and extrinsic variables.39,41–44,46,187,189

What complicates the identification and quantifica-tion of risk is that, in many situations, risk factors interact. Meeuwisse39 proposed a model that accommodates a mul-tifactorial assessment of causation in athletic injuries. In that model, intrinsic factors are viewed as factors that pre-dispose an athlete or dancer to react in a specific manner to an injury situation; then, once the athlete or dancer is predisposed, extrinsic, or enabling, factors may facilitate manifestation of injury (Figure 6).39

The heterogeneity of predisposing and outcome fac-tors often render a correlation between risk and cause sta-tistically and clinically insignificant.187 So, while certain intrinsic and extrinsic factors may render the dancer sus-ceptible to injury, they are often not enough to trigger an injury occurrence. Rather, a constellation of factors sum or interact in such a way as to make the dancer vulnerable for an injury event ( Figure 4).39

Best PracticeBest practice in dance medicine and science is de-

fined as behavior that furthers the profession’s capability to prevent, diagnose, rehabilitate, and enhance the health and functional abilities of members of the dance commu-nity.191 How, then, should the dance medicine profession best advance its aims to be effective in reducing risk and injury occurrence and avoid repeating anew efforts of the past that have not achieved optimal success? If the un-derstanding of dance injury epidemiology is to advance, a multifactorial approach must be taken when assessing etiology or causation. Multifactorial analyses can yield a more complete understanding of injury causality and lead to the advancement of a scientific basis for the develop-ment of specific treatment and prevention guidelines.192

Screening and Injury ReportingDespite enormous challenges posed by cause-determi-

nation research, it is plausible, with time and careful ob-servation, to quantify risks for dancers with some certainty by measuring the proportion of injured persons relative to the at-risk population and comparing exposure to the ac-tivity in both the injured and uninjured members of the group. This is done in industry and sport by systematic reporting of injury. Injury reporting, also referred to as in-jury surveillance, is an ongoing collection, analysis, and interpretation of data related to occupational exposures in a work environment and to adverse health outcomes asso-ciated with exposure to work.5,193 One well-accepted way to use injury surveillance data effectively is to employ a sequence-of-prevention model.194 Such a model evaluates preparticipation screening data in the context of a broader longitudinal health care system that addresses the biopsy-chosocial aspects38 of the dancer’s life relative to an ongo-ing and iterative injury-reporting analysis (Figure 7).

This process allows practitioners to observe injury oc-currence not only relative to measured intrinsic attributes of dancers, but also relative to the complex interplay be-tween those variables and environmental elements in the dance workplace, all tempered by the dancers’ under-standing of their role and responsibilities with respect to the health care process and the variable nature of dancer state versus trait depending upon situational factors at any given time.

Figure 7 illustrates an iterative process that begins at step 1 with identification of the magnitude of injury rates by standardized and reliable methods,5 followed in step 2 by identification of the factors and mechanisms that play a role in the injury-illness events. Once that information is collected, step 3 is to introduce measurable interven-tions that are likely to counter the variables identified in

Time

prior injury history

laxity

age

sex

Mechanism of Injury Proximal to Outcome

Risk Factors for Injury Distant from Outcome

Inciting Event

Predisposed Dancer

Susceptible Dancer

Injury

Exposure to Extrinsic Risk Factors Intrinsic Risk Factors

body mass index

strength

Figure 6. Multifactorial model of injury etiology modified for dance. Reprinted with permission from Clinical Journal of Sports Medicine.39 Copyright 1994, Wolter Kluwer Health.

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step 2 as an attempt to reduce future risk. Last, in step 4 the effect of the step-3 interventions are evaluated by re-peating step 1 to see if a reduction in injury rates indeed occurred.

A sequence-of-prevention model works because it takes into account dancer outcomes. Outcome-oriented methodology is defined as the study of what works.195 It evolved in health care to answer clinical management questions in a scientifically valid manner196 and to provide a means by which health care providers, dancers, parents, teachers, and dance companies could identify the effec-tiveness of various interventions and decide whether they are cost-effective.

Ellwood197 described the 4 elements of outcome man-agement as: (1) an emphasis on patient-based measures; (2) an emphasis on large and more inclusive databases; (3) the development of practice guidelines; and (4) a cycle of continuous improvement, whereby practice guidelines based on research using patient-based outcomes would lead to improved care.

Outcome measures are geared toward the measure-ment of a dancer’s functional status and quality of life over time using terms relevant to the dancer and the task. It is a way of using the dancer’s experience to facilitate better insight into the effectiveness of an intervention. The goal behind outcomes research is to standardize care by first assessing a wide variety of treatment approaches to a com-mon problem and monitoring results. From an analysis of such results, the treatment approach yielding the best outcome can then be made available to all dancers. This type of clinical research is a best-practice approach for en-abling true reduction of injury incidence over time. It is a practical way of applying epidemiologic science to dance medicine.

On-site CareIt is also known from the literature that establishing

on-site health care at dance schools and companies is an effective way to reduce injury incidence and medi-cal costs.8,21,198,199 These programs ensure dancers priva-cy while also providing them with timely and affordable

access to qualified health care practitioners, function-specific tests and measures, and progression protocols that consider all aspects of their occupational demands (Tables 2 to 4).

When working on-site, it is important for the thera-pist to remember that danc-ers are often training up to 10 hours per day, and this training volume must be accounted for when devel-oping rehabilitation proto-cols.20,32 Often this work-

load is performed while also restricting calories. In addi-tion, as discussed in a prior section of this monograph, it is important for therapists to be cognizant that injuries fre-quently produce feelings of depression.200,201 Values such as perfectionism and daily personal bests are ingrained in the dancer. Relative rest and time out from some activi-ties to restore function progressively is anathema to their sense of professional responsibility as well as to the main-tenance of their identity and self-worth. Injured dancers report being fearful of harsh judgment from peers (eg, be-ing perceived as unreliable, weak, or lazy). They are also fearful of the loss of performance opportunities, and thus hide their pain or deny their injury at its initial onset. Fifty-eight percent of students perform against medical advice and 47% of professionals continue to work injured be-cause they are fearful to seek medical attention. Forty-four percent report feeling hopeless, anxious, angry, and frustrated and 35% present with frank clinical depression, 100% of whom have suicidal thoughts.200,201

Depression is characterized by feelings of sadness, emptiness, and tearfulness that last for most of the day, as well as a loss of interest or pleasure that lasts for at least 2 weeks. A dancer suffering from depression might experi-ence the following symptoms200:• Significant changes in appetite resulting in weight gain or loss.• Insomniaorhypersomnia.• Psychomotoragitation.• Fatigueorlossofenergy.• Feelings of worthlessness or excessive or inappro- priate guilt (increased self-criticism).• Diminished ability to think or concentrate; indeci- siveness.• Thoughtsofdeathorsuicidethatarerecurrent.

On-site care will be most successful when it incorpo-rates a regional interdependent examination approach202 and a biopsychosocial perspective, addressing affective and cognitive elements into the determination of progno-sis and encouraging a sense of self-efficacy as well as ac-complishment of neuromuscular control and restoration of occupational-specific musculoskeletal function.203,204

Figure 7. The sequence-of-prevention model. Reprinted with permission from Sports Medicine.194 Copyright 1992, Wolter Kluwer Health.

1. Extent of injury-illness measured with standardized injury-reporting system

2. Factors or mechanisms related to injury-illness occurrence are identified

4. Outcomes measured 3. Implementation of measurable interventions targeted to reduce associated risk factors

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Table 3. Functional Progressions for Dance*

Parameter Basic Level Progressed Level

Movement patterns - Pedestrian stance and gait - Ballet stances and skills

Cardiovascular - 20 to 40 minutes, 4 times per week- Target heart rate

- 40 minutes, 4 times per week- Alternate aerobic with anaerobic bouts of ratio 2-minute

maximum heart rate

Strength - Wide, parallel base - Proximal resistance keeping trunk in sagittal plane

- Sagittally restricted turned-out base - Digital resistance- Moving trunk and upper extremities- Head and eye focus throughout frontal and transverse planes

Exercise tempos - Slower - Faster

Mechanical loads - Lighter - Heavier

Balance - Two legs- Grounded base of support (eg, plié)

- Single leg- Narrow base of support (eg, relevé)

Surface - Stable floor - Trampoline, sand, mattress, moving treadmill

Vision - Eyes open- Comfortable light level

- Eyes closed- Dim or very bright light level

Jumping - Low height, low repetitions- 2 feet

- High height, moderate repetitions- 1 foot

Concentration - Perform simple verbal recall while performing balance task on stable floor surface

- Perform complex verbal recall while executing balance tasks on unstable surface; reverse

*Reprinted with permission from Liederbach M.48 Copyright 2000, J Michael Ryan Publishers.

Table 2. 4-Stage Progressive Rehabilitation Protocol*

Rehabilitation Stage Clinical Goals Studio Goals

Stage 1: restricted - Reduce swelling and pain- Active rest- Evaluate kinetic chain for dysfunction- Aerobic conditioning

- Restrict tissue loading- Somatics and mental practice- Take floor exercise class or pool class

Stage 2: restoration - Restore range of motion and strength- Progress aerobic conditioning- Begin functional weight bearing and basic skills

- Permit limited movement with restricted tissue loading (eg, padding, taping)

- Concentrate on alignment and stability- Take beginner level dance class

Stage 3: reacquisition - Progress strength to supernormal levels- Bilateral unilateral weight bearing- Eyes open eyes closed- Slow fast movement exercise

- Return to original level class- Progress from 1 class per day to more, as tolerated- Limit number of jumps and rehearsals

Stage 4: refinement - Build confidence, carriage, and control187

- Complicate skills- Progress cardiovascular drills- Increase speed and loads- Progress dynamic balance- Increase repetitions

- Unrestricted dance movement- Prescribed warm-up- Implementation of injury management and prevention

techniques learned in rehabilitation- Understanding of nutritional needs discussed during

rehabilitation

*Reprinted with permission from Liederbach M.48 Copyright 2000, J Michael Ryan Publishers.

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Table 4. Selected Functional Tests in Dance*

Parameter Example of Task Score Unit

Balance - Romberg-type test - Time

Agility - Direction-oriented, dance-specific reaction time drills - Number of successful completions with time limitations imposed

Concentration - Movement task with changing instructions in chaotic environment

- Number of successful completions with sound and space distractions imposed

Proprioception - Balance tests: changing lights and surface- Proprioception tests

- Time- Goniometric accuracy: joint angle replication

Trunk strength and endurance

- Pike sit-ups with mobile upper extremities - Number of repetitions without fatigue-induced movement errors

Trunk power - Transfer of lower extremity weight- Efficiency of lower extremity placement following change in

body level or directional facing

- Number of stable transfers completed- Number of successful foot placements with

time-dependent level or direction changes

Lower extremity strength - Unilateral limb wall sits - Time

Lower extremity power - Unilateral sauté jumps

- Unilateral jeté jumps

- Height and/or number of repetitions without fatigue-induced movement errors

- Horizontal distance

*Reprinted with permission from Liederbach M.48 Copyright 2000, J Michael Ryan Publishing.

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NOTES

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Prevalence of injury in dance is reported to be:1. 50% to 70%.a. 75% to 97%.b. 10% to 20%.c. 25% to 38%.d.

Dance is considered to be a:2. high-risk activity.a. low-risk activity.b. low-risk to moderate-risk activity.c. moderate-risk to high-risk activity.d.

The average cost of a minor dance injury is 3. estimated to be:

between $4500 and $6000.a. between $1300 and $3000.b. between $2800 and $4500.c. $10,000.d.

Injuries in dance are most common in the:4. foot and ankle of lesser skilled dancers.a. hip of amenorrheic dancers.b. knee of older dancers.c. spine of women dancers.d.

Injuries in dance can be predicted what percentage 5. of the time by trait anxiety?

97%.a. 61%.b. 25%.c. 2%.d.

Orthopaedic Section Independent Study Course 18.3.1

Epidemiology of Dance Injuries: Biopsychosocial Considerations in the Management of Dancer Health

REVIEW QUESTIONS

In the 1970s, dance was considered to be as dangerous 6. as:

fencing and rowing.a. football and bull fighting.b. soccer and basketball.c. volleyball and baseball.d.

Which injury results in the second most common 7. reason for time lost from work as a dancer?

Achilles tendonitis.a. ankle sprain.b. anterior cruciate ligament sprain.c. low back pain.d.

Women ballet dancers average what percentage of 8. expected body weight?

88%.a. 58%.b. 95%.c. 75%.d.

What percentage of university dancers report 9. symptoms of depression?

43%.a. 90%.b. 72%.c. 28%.d.

What percentage of dancers make it to the professional 10. stage?

1%.a. 10%.b. 0.1%.c. 0.01%.d.

ANSWERS

1. b

2. c

3. b

4. a

5. b

6. b

7. b

8. d

9. a

10. c