A profile of the musculoskeletal characteristics of elite professional ballet dancers* WILLIAM G. HAMILTON,† MD, LINDA H. HAMILTON, PhD, PETER MARSHALL, MA, PT, AND MARIKA MOLNAR, MA, PT
From The Miller Health Care Institute for Performing Artists, St. Luke’s-Roosevelt Hospital Center, New York, New York
development in dancers.8,14 Ballet is also unique in that it is not simply an athletic activity, but a performing art. As an interpretive artist, the professional dancer is expected to be creative, while executing difficult steps in front of a live audience. The physical and mental stresses inherent in this endeavor often weed out those unsuited to the profession-
ABSTRACT
Twenty-eight principal dancers and soloists from America’s two most famous ballet companies were examined for anthropometric measurements, including flexibility, muscle strength, and joint range of motion. Both male and female dancers were flexible, but not hypermobile, and did not differ significantly from each other.
similar to Darwin’s concept of the selection of the fittest.8 Dancers who go into ballet with the wrong bodies may incur many problems, from traumatic arthritis to anorexia ner-
Marked differences were found between the range of motion of the hip and ankle in the dancers and the norms for the general population. The increased external rotation of the hip in women was accompanied by a loss in internal rotation, resulting in an increased range of motion with an externally rotated orientation. The men, however, lost more internal rotation than they gained in external rotation. These data raise the possibility of a torsional component to the turned-out hip position in elite female professional ballet dancers. In addition, significant anatomic differences separate elite dancers of both sexes from the normal population.
vosa. 8,9 As dancers pursue their careers, injuries and mental strain inevitable. To provide health care for the dancer, a special division within sports medicine has evolved. However, until recently there was little information in the medical literature to which practitioners could refer. This problem is now beginning to be rectified, as some of the consequences of the aesthetics of ballet are being explored. Major areas of interest include acute injuries, stress fractures, scoliosis, menstrual irregularities, eating disorders, and psyare
chological factors. 4,7,10,13-15,23 While these studies provide essential information on ballet dancers, many are limited in that they often generalize from the student to the professional dancer, or fail to distinguish between the two. In addition, except for one study on eating disorders,9 no differentiation has yet been made between the national and regional dancer, where different standards for technique, competitive level, length of performance season, and emphasis on thinness may exist. These differences are particularly evident in studies on musculoskeletal characteristics, where information has been garnered from dance students and regional dancers.13, 14, 15 Sapega et al. 19 have established an ideal physical profile for the Olympic fencer that now serves as a norm for comparison in evaluating and rehabilitating United States national team fencers with orthopaedic problems. In line with this concept, we have attempted to establish
Musculoskeletal profiles have been established for Olympic and professional athletes as an aid in training, competition, and injury prevention.&dquo;,&dquo; Research in sports medicine has shown that classical ballet is equal to professional football in the physical demands of athletic performance17; however, no profile has been established for the elite, &dquo;Olympic level&dquo; professional dancer. Classical ballet is a highly stylized and, in many ways, artificial art form that requires a very specific body type. This is reflected in the unusual patterns of musculoskeletal Presented in part at the Sixth Annual Symposium on Medical Problems of Musicians and Dancers, Aspen, Colorado, July 1988. t Address correspondence and reprint request to: William G. Hamilton, MD, 345 West 58th Street, New York City, NY 10019. *
267
268
psychologicalll
Flexibility
MATERIALS AND METHODS
Musculoskeletal flexibility was obtained using Nicholas’ six flexibility tests.&dquo; The results for both right and left side were numerically graded on a 0 to 3 point scale, determined by the individual’s ability to passively assume the body
and physical profiles for the high-level This paper presents the musculoskeldancer. professional etal profile of this group.
Subjects Twenty-eight principal dancers and soloists who were performing for American Ballet Theater and the New York City Ballet participated in this study. There were 14 women and 14 men, ranging in age from 22 to 41 years (mean for women, 29.23 ± 5.25; mean for men, 28.42 ± 4.08). Dancers were excluded from this study if they were currently injured or not performing on a regular basis, i.e., partially retired and performing &dquo;character&dquo; roles. Our sample represented 64% of the active principal dancers and soloists in the two companies. At the time of the study, both companies were in the middle of their spring season at Lincoln Center, New York City, and the subjects were typically dancing 8 hours a day, 6 days a week. Procedure After written informed consent was obtained, all of the subjects were examined at the Eastside Dance Physical Therapy Center in New York City. The tests were done in one session by a team of physical therapists arranged in &dquo;stations,&dquo; so that one observer performed the same test on each subject. All of the procedures were conducted under the supervision of the orthopaedist in the group. For reliability, each test was performed three times. The result reported was the average of the three measurements. The dancers had not taken class or performed that day.
Demographics Subjects
were
asked to
complete
a
questionnaire regarding
age, education, dance training, dominant hand, turning preference, years as a professional, and history of injuries. Women were asked to give the age they began pointe work, their age of menarche, and if they had menstrual irregularity or amenorrhea (no menses for longer than 5 months). The average age of menarche in the United States is 12.5 years.’
Subject measurements For each subject, height, weight, and percent of ideal body weight for height2° were recorded, as well as gross measurements, including trunk length, arm span, arm length, and leg length. All of the dancers were examined for bunions and scoliosis by the orthopaedist in the group. The determination for scoliosis was based on spinal and rib asymmetry on forward bending, while leg-length inequality was corrected. The incidence of scoliosis in the general population is 3.9% in women and 0.5% in men.24
positions specified in the test: elbow hyperextension, external arm rotation, external leg rotation, knee recurvatum, and palms to floor. Lotus position (full external rotation of the hips in flexion) was graded on a 0 to 1 point scale. Hypermobility was defined as a total score of 10, omitting turnout and palms to floor, which are acquired through selection and
Muscular
training.
strength
A
Cybex (Lumex Inc, Ronkonoma, NY) isokinetic dynaassess muscular strength at 60 deg/sec/foot-pounds. At this speed, subjects with ideal strength should be able to lift their body weight in pounds with their knee extensors.’ The following muscle groups were tested, ratios determined, and then compared to norms for other athletes: hip abduction, adduction, and abduction/ adduction ratio’; knee extension, flexion, and extension/ flexion ratio’; and ankle plantar flexion, dorsiflexion, and plantar flexion/dorsiflexion ratio.’ Strength for right and mometry system was used to
left limbs
was recorded. A Cybex table was used to position and stabilize the lower body, supplemented by manual immobilization by the tester. Correction factors were calculated for the weight of the input lever. Five submaximal repetitions were used as a warmup before the maximum effort, with the highest peak torque taken as a measurement of strength. To avoid confusion between overshoot torque spikes and true peak muscle torque spikes, a damping setting of 2 was used on the Cybex recorder.
Range of motion Range of motion (ROM) in the lower extremity was recorded using standard goniometers. Norms for the general population were used for the following comparisons: hip external rotation/internal rotation (prone)21; hip external rotation/ internal rotation (sitting)21; hip abduction/adduction (supine)’; hip flexion (supine)’; knee flexion/extension, hyperextension, tibial torsion’; tibial external rotation/internal rotation (knee flexed)16; &dquo;pli6&dquo; dorsiflexion (ankle dorsiflexion with knee flexed); ankle plantar flexion/dorsiflexion (knee in extension).’ Statistics
Fischer’s Exact test and t-tests were used to compare results on the dichotomous and continuous variables, respectively. These analyses were performed by a statistician using the
SPSS/PC program (SPSS Inc, Chicago, IL).
269
RESULTS
Demographic and subject characteristics The physical characteristics of the dancers are listed in Table 1. Differences were not found between the New York 14) and the American Ballet City Ballet dancers (N Theater dancers (N 14). Male and female dancers differed for height, weight, percent ideal weight, age when training started, and presence of bunions. The women were considerably below their ideal weight, while the men were equal to the norm. Female dancers also began training 4 years earlier than males. More than half of the women had bunions versus 10% of the men. Most of the bunions were mild. A higher than normal incidence of scoliosis was found in both sexes. Based on visual appraisal, the curves were less than 25°. All of the women and 75% of the men turned more easily to the right than to the left side. This turning preference was not associated with upper-extremity dominance. The women began pointe work before puberty. A delay in menarche of 3 years was noted, as was a high incidence of menstrual irregularity and amenorrhea.
flexibility, the men and women scored 10 points of a possible 16, putting them in the hypermobile range. However, if palms to floor and external rotation of the lower extremity are excluded, the dancers scored 4 points of a possible 10, putting them in the average range of flexibility.
=
=
Flexibility The results of the flexibility testing are listed in Table 2. Male and female dancers did not differ significantly from each other. All had increased flexibility in external arm rotation, external leg rotation, and palms to floor (positions common in ballet technique). However, both groups had difficulty assuming the lotus position. In terms of total TABLE1 Characteristics of the
subjects
Muscle
strength
Because of characteristic differences between the sexes, muscle strengths of men and women were analyzed separately. In the men, there was a striking imbalance between the hip abductors (+18%) and adductors (-25%) when compared to normal (Table 3). This resulted in a significant reversal of the usual abduction/adduction ratio when the averaged right and left sides were compared to the norm. Weakness was found in the knee extensors (-16% ) and flexors (-18%), but the extensor/flexor ratio was normal. Thus, although weakness was present, the muscle groups retained their strengths in relation to each other. The ankle plantar flexors (+44%) and dorsiflexors (+40%) were significantly stronger than expected; however, the ratio of their strengths also remained in proportion. The men showed no statistically significant differences between the right and left sides for hip, knee, and ankle strength. The women exhibited the same reversal of strengths between the abductors (+21%) and adductors (-24%) of the hip (Table 4) seen in the men. The abduction/adduction ratio was also significantly reversed. The women did not have the strength deficits about the knee found in the men, as their knee strengths were normal. Similar to the men, their extensor/flexor ratios were normal. The strength in their ankles was even greater than the men for their size. Their plantar flexors (+33%) and dorsiflexors (+26%) were significantly above the norm, but their plantar flexion/ dorsiflexion ratio again was normal. The muscles of the hip and knee in the women were significantly stronger in the right leg compared to the left. TABLE 3 Male muscular strength data-mean peak torque (in
° Women
versus
’Women
versus
men, P < men, P
From The Miller Health Care Institute for Performing Artists, St. Luke’s-Roosevelt Hospital Center, New York, New York
development in dancers.8,14 Ballet is also unique in that it is not simply an athletic activity, but a performing art. As an interpretive artist, the professional dancer is expected to be creative, while executing difficult steps in front of a live audience. The physical and mental stresses inherent in this endeavor often weed out those unsuited to the profession-
ABSTRACT
Twenty-eight principal dancers and soloists from America’s two most famous ballet companies were examined for anthropometric measurements, including flexibility, muscle strength, and joint range of motion. Both male and female dancers were flexible, but not hypermobile, and did not differ significantly from each other.
similar to Darwin’s concept of the selection of the fittest.8 Dancers who go into ballet with the wrong bodies may incur many problems, from traumatic arthritis to anorexia ner-
Marked differences were found between the range of motion of the hip and ankle in the dancers and the norms for the general population. The increased external rotation of the hip in women was accompanied by a loss in internal rotation, resulting in an increased range of motion with an externally rotated orientation. The men, however, lost more internal rotation than they gained in external rotation. These data raise the possibility of a torsional component to the turned-out hip position in elite female professional ballet dancers. In addition, significant anatomic differences separate elite dancers of both sexes from the normal population.
vosa. 8,9 As dancers pursue their careers, injuries and mental strain inevitable. To provide health care for the dancer, a special division within sports medicine has evolved. However, until recently there was little information in the medical literature to which practitioners could refer. This problem is now beginning to be rectified, as some of the consequences of the aesthetics of ballet are being explored. Major areas of interest include acute injuries, stress fractures, scoliosis, menstrual irregularities, eating disorders, and psyare
chological factors. 4,7,10,13-15,23 While these studies provide essential information on ballet dancers, many are limited in that they often generalize from the student to the professional dancer, or fail to distinguish between the two. In addition, except for one study on eating disorders,9 no differentiation has yet been made between the national and regional dancer, where different standards for technique, competitive level, length of performance season, and emphasis on thinness may exist. These differences are particularly evident in studies on musculoskeletal characteristics, where information has been garnered from dance students and regional dancers.13, 14, 15 Sapega et al. 19 have established an ideal physical profile for the Olympic fencer that now serves as a norm for comparison in evaluating and rehabilitating United States national team fencers with orthopaedic problems. In line with this concept, we have attempted to establish
Musculoskeletal profiles have been established for Olympic and professional athletes as an aid in training, competition, and injury prevention.&dquo;,&dquo; Research in sports medicine has shown that classical ballet is equal to professional football in the physical demands of athletic performance17; however, no profile has been established for the elite, &dquo;Olympic level&dquo; professional dancer. Classical ballet is a highly stylized and, in many ways, artificial art form that requires a very specific body type. This is reflected in the unusual patterns of musculoskeletal Presented in part at the Sixth Annual Symposium on Medical Problems of Musicians and Dancers, Aspen, Colorado, July 1988. t Address correspondence and reprint request to: William G. Hamilton, MD, 345 West 58th Street, New York City, NY 10019. *
267
268
psychologicalll
Flexibility
MATERIALS AND METHODS
Musculoskeletal flexibility was obtained using Nicholas’ six flexibility tests.&dquo; The results for both right and left side were numerically graded on a 0 to 3 point scale, determined by the individual’s ability to passively assume the body
and physical profiles for the high-level This paper presents the musculoskeldancer. professional etal profile of this group.
Subjects Twenty-eight principal dancers and soloists who were performing for American Ballet Theater and the New York City Ballet participated in this study. There were 14 women and 14 men, ranging in age from 22 to 41 years (mean for women, 29.23 ± 5.25; mean for men, 28.42 ± 4.08). Dancers were excluded from this study if they were currently injured or not performing on a regular basis, i.e., partially retired and performing &dquo;character&dquo; roles. Our sample represented 64% of the active principal dancers and soloists in the two companies. At the time of the study, both companies were in the middle of their spring season at Lincoln Center, New York City, and the subjects were typically dancing 8 hours a day, 6 days a week. Procedure After written informed consent was obtained, all of the subjects were examined at the Eastside Dance Physical Therapy Center in New York City. The tests were done in one session by a team of physical therapists arranged in &dquo;stations,&dquo; so that one observer performed the same test on each subject. All of the procedures were conducted under the supervision of the orthopaedist in the group. For reliability, each test was performed three times. The result reported was the average of the three measurements. The dancers had not taken class or performed that day.
Demographics Subjects
were
asked to
complete
a
questionnaire regarding
age, education, dance training, dominant hand, turning preference, years as a professional, and history of injuries. Women were asked to give the age they began pointe work, their age of menarche, and if they had menstrual irregularity or amenorrhea (no menses for longer than 5 months). The average age of menarche in the United States is 12.5 years.’
Subject measurements For each subject, height, weight, and percent of ideal body weight for height2° were recorded, as well as gross measurements, including trunk length, arm span, arm length, and leg length. All of the dancers were examined for bunions and scoliosis by the orthopaedist in the group. The determination for scoliosis was based on spinal and rib asymmetry on forward bending, while leg-length inequality was corrected. The incidence of scoliosis in the general population is 3.9% in women and 0.5% in men.24
positions specified in the test: elbow hyperextension, external arm rotation, external leg rotation, knee recurvatum, and palms to floor. Lotus position (full external rotation of the hips in flexion) was graded on a 0 to 1 point scale. Hypermobility was defined as a total score of 10, omitting turnout and palms to floor, which are acquired through selection and
Muscular
training.
strength
A
Cybex (Lumex Inc, Ronkonoma, NY) isokinetic dynaassess muscular strength at 60 deg/sec/foot-pounds. At this speed, subjects with ideal strength should be able to lift their body weight in pounds with their knee extensors.’ The following muscle groups were tested, ratios determined, and then compared to norms for other athletes: hip abduction, adduction, and abduction/ adduction ratio’; knee extension, flexion, and extension/ flexion ratio’; and ankle plantar flexion, dorsiflexion, and plantar flexion/dorsiflexion ratio.’ Strength for right and mometry system was used to
left limbs
was recorded. A Cybex table was used to position and stabilize the lower body, supplemented by manual immobilization by the tester. Correction factors were calculated for the weight of the input lever. Five submaximal repetitions were used as a warmup before the maximum effort, with the highest peak torque taken as a measurement of strength. To avoid confusion between overshoot torque spikes and true peak muscle torque spikes, a damping setting of 2 was used on the Cybex recorder.
Range of motion Range of motion (ROM) in the lower extremity was recorded using standard goniometers. Norms for the general population were used for the following comparisons: hip external rotation/internal rotation (prone)21; hip external rotation/ internal rotation (sitting)21; hip abduction/adduction (supine)’; hip flexion (supine)’; knee flexion/extension, hyperextension, tibial torsion’; tibial external rotation/internal rotation (knee flexed)16; &dquo;pli6&dquo; dorsiflexion (ankle dorsiflexion with knee flexed); ankle plantar flexion/dorsiflexion (knee in extension).’ Statistics
Fischer’s Exact test and t-tests were used to compare results on the dichotomous and continuous variables, respectively. These analyses were performed by a statistician using the
SPSS/PC program (SPSS Inc, Chicago, IL).
269
RESULTS
Demographic and subject characteristics The physical characteristics of the dancers are listed in Table 1. Differences were not found between the New York 14) and the American Ballet City Ballet dancers (N Theater dancers (N 14). Male and female dancers differed for height, weight, percent ideal weight, age when training started, and presence of bunions. The women were considerably below their ideal weight, while the men were equal to the norm. Female dancers also began training 4 years earlier than males. More than half of the women had bunions versus 10% of the men. Most of the bunions were mild. A higher than normal incidence of scoliosis was found in both sexes. Based on visual appraisal, the curves were less than 25°. All of the women and 75% of the men turned more easily to the right than to the left side. This turning preference was not associated with upper-extremity dominance. The women began pointe work before puberty. A delay in menarche of 3 years was noted, as was a high incidence of menstrual irregularity and amenorrhea.
flexibility, the men and women scored 10 points of a possible 16, putting them in the hypermobile range. However, if palms to floor and external rotation of the lower extremity are excluded, the dancers scored 4 points of a possible 10, putting them in the average range of flexibility.
=
=
Flexibility The results of the flexibility testing are listed in Table 2. Male and female dancers did not differ significantly from each other. All had increased flexibility in external arm rotation, external leg rotation, and palms to floor (positions common in ballet technique). However, both groups had difficulty assuming the lotus position. In terms of total TABLE1 Characteristics of the
subjects
Muscle
strength
Because of characteristic differences between the sexes, muscle strengths of men and women were analyzed separately. In the men, there was a striking imbalance between the hip abductors (+18%) and adductors (-25%) when compared to normal (Table 3). This resulted in a significant reversal of the usual abduction/adduction ratio when the averaged right and left sides were compared to the norm. Weakness was found in the knee extensors (-16% ) and flexors (-18%), but the extensor/flexor ratio was normal. Thus, although weakness was present, the muscle groups retained their strengths in relation to each other. The ankle plantar flexors (+44%) and dorsiflexors (+40%) were significantly stronger than expected; however, the ratio of their strengths also remained in proportion. The men showed no statistically significant differences between the right and left sides for hip, knee, and ankle strength. The women exhibited the same reversal of strengths between the abductors (+21%) and adductors (-24%) of the hip (Table 4) seen in the men. The abduction/adduction ratio was also significantly reversed. The women did not have the strength deficits about the knee found in the men, as their knee strengths were normal. Similar to the men, their extensor/flexor ratios were normal. The strength in their ankles was even greater than the men for their size. Their plantar flexors (+33%) and dorsiflexors (+26%) were significantly above the norm, but their plantar flexion/ dorsiflexion ratio again was normal. The muscles of the hip and knee in the women were significantly stronger in the right leg compared to the left. TABLE 3 Male muscular strength data-mean peak torque (in
° Women
versus
’Women
versus
men, P < men, P
