Anthropometric measurements of young ballet dancers: examining body composition, puberty, flexibility, and joint range of motion in comparison with non-dancer controls.
Previous studies have examined the physical characteristics of adolescent and adult ballet dancers, but there is little information in the literature about the child dancer. The purpose of this case control study was to compare body composition, sexual maturity, flexibility, and joint range of motion measurements between child ballet dancers and age-matched, non-dancer controls. Subjects included 43 female dance students from a school affiliated with a nationally known ballet company and 43 female age-matched students from local public schools, ranging in age from eight to thirteen years. Height, weight, and Tanner stages were recorded. Body fat (by bioelectrical impedance analysis), flexibility, and joint range of motion were measured. There were no significant differences between the dancers (D) and non-dancers (ND) in height. Significant differences were found in mass: 30.4 [+ or -] 5.5 kg (D) versus 41.6 [+ or -] 13.3 kg (ND), p < 0.01; percentage body fat: 13.2% [+ or -] 4.8% (D) compared to 20.7% [+ or -] 6.7% (ND), p < 0.001; and Tanner stage: 1.442 [+ or -] 0.502 (D) versus 1.953 [+ or -] 0.754 (ND), p < 0.0004. The dancer group scored significantly higher in four of the six Nicholas' flexibility tests (p < 0.0001) and in 20 out of 24 joint range of motion measurements (p < 0.05). In conclusion, child dancers were significantly leaner, more flexible, and sexually immature when compared to age-matched, non-dancer controls.
Several studies have concluded that children and adolescents today are seemingly as fit as those a decade or two ago, but are fatter. (1-3) In a 1995 study of 6,700 girls aged seven to seventeen years, Malina and colleagues (4) demonstrated that the fattest 5% in each age group of girls performed significantly worse than the leanest 5% on both health-related fitness (including flexibility) and motor fitness tests. In 2003, Prista and associates (5) also found that overweight children did not perform as well as normal or underweight children on most physical fitness tests.
Perhaps related to increased weight and adiposity among children, girls today are also developing pubertal characteristics at an earlier age than recorded in previous decades. (6) In 1997, Herman-Giddens and coworkers (7) found that the mean onset for breast development was 8.87 [+ or -] 1.93 years for African-American girls and 9.96 [+ or -] 1.82 years for Caucasian girls; in contrast, Marshall and Tanner (8) in 1969 reported a mean age of 11.15 [+ or -] 1.10 years for breast development onset among Caucasian girls. This trend of earlier development is also reflected in average menstrual onset. In comparing the National Health Examination Survey cycles II and III (1963-1970) with the Third National Health and Nutrition Examination Survey (1988-1994), Anderson and colleagues (6) demonstrated that the average age at menarche dropped from 12.75 to 12.54 years within 25 years. In 1997, Herman-Giddens and associates (7) reported 12.16 [+ or -] 1.21 years in African-American girls and 12.88 [+ or -] 1.20 years in Caucasian girls, while Marshall and Tanner (8) reported a mean average age of menarche of 13.47 [+ or -] 0.10 years in 1969.
On the other hand, when looking at adults, it is well-documented that female ballet dancers have leaner body masses and are overall more fit and flexible than average women. (9-14) It has also been shown that female ballet dancers have a higher incidence of amenorrhea, irregular menstruation, and delayed menarche. (15-20) Ballet is a highly active sport that promotes leanness, yet extreme leanness is associated with delayed menarche and potential for injury. The body composition, fitness, and developmental effects of intense ballet training on young girls have not been fully examined.
Most studies on ballet dancers' body composition and flexibility have been conducted on adults. (12-14,16,21-23) Fewer studies have examined body characteristics of the adolescent ballet dancer, while studies on pre-adolescent and child ballet dancers are even more scarce. In 1989, Clarkson and coworkers (21) found that characteristics associated with the professional ballet dancer body, such as smaller upper arms and larger calf and ankles than the reference female, were apparent in adolescent ballet dancers (mean age 15.1 [+ or -] 1.4 years for the youngest group in their study). Young adult dancers (age 16 to 18 years) were also found to have greater joint range of motion than controls. (10,14) In a four-year study following ballet dancers initially aged 13 to 15 years, Warren, (19) in 1980, found that dancers had lower body weight, lower calculated body fat, and delayed menarche when compared to non-dancer controls.
These past studies have shown that the leanness and flexibility characteristic of professional ballet dancers is clearly observable in adolescent, teenage ballet dancers. A question that remains, then, is how early do these body characteristics become apparent? In 1993, Nilsson and colleagues (24) compared first year ballet students (aged 10 years) with controls and noted a higher incidence of joint laxity and greater flexibility in the ballet students, despite little training before entering the ballet school. This suggests that selection factors play a strong role in the increased joint mobility seen in dancers. In 1999 and 2001, Bennell and associates (25,26) examined hip and ankle range of motion in ballet students and controls (mean age 9.6 [+ or -] 0.8 years) and found that dancers had less hip rotational range than controls but greater non-hip external rotation; the dancers also had greater ankle dorsiflexion. These investigators found that both dancers and controls increased their total hip range of motion but not ankle dorsiflexion over the course of a year. In 1997, Pigeon and coworkers (18) studied the effects of dance on growth and puberty among young dancers (mean age 12.6 [+ or -] 0.9 years) and found that puberty was delayed in the dancers compared to controls and that growth velocity was decreased during the pre-puberty stage in several of the dancers.
Our study examined the body composition, joint range of motion, and flexibility as well as developmental effects of intense ballet training on young girls aged eight to thirteen. Our hypothesis was that there is no difference between ballet students and control non-dancer students in terms of puberty (Tanner stage) and body composition at such a young age. We also investigated joint range of motion and flexibility for comparison with the other studies.
Materials and Methods Subjects
Forty-three young female dance students from the Boston Ballet School and 43 age-matched non-dancer female students from three local schools participated in the study. None of the control subjects participated in organized ballet. The average age for the dancer group was 10.4 [+ or -] 1.2 years (range: 8 to 13 years) and 10.4 [+ or -] 1.4 years (range: 8 to 13 years) for the non-dancer group. All participants and their parents signed a consent form. The study was approved by the Children's Hospital Committee on Clinical Investigation and the Boston Ballet School. All subjects were given a questionnaire in order to determine age, age at which they started training (in dance or other sport activities), and hours per week of organized sport or dance. Dancers were also asked for the number of years of training that they had in which they trained for a period of two or more classes per week.
Standing height was measured with the subject in stocking feet using a wall-mounted ruler. A second rigid ruler was placed on the crown of the head at a 90[degrees] angle to the wall and height was recorded to the nearest 0.3 cm. Weight was measured to the nearest 0.1 kg on a triple beam balance with the subject in gym clothes or ballet clothes without shoes. Body mass index (BMI) was calculated from height and mass data.
Percentage Body Fat
Percentage body fat was determined by the bioelectrical impedance method. Electrodes were placed on four locations: the dorsal aspect of the wrist between the styloid and radial processes, the first digit (proximal to the distal interphalangeal joint), the ankle between the two malleoli, and the great toe. Impedance was recorded and percentage body fat was obtained using the electrolipogram (Bioanalogic, Beaverton, Oregon).
Tanner Stage Estimate
Tanner stage was estimated for all subjects by pediatrician author LFG using the method of Tanner. (27) Estimation was based on breast development and a check for axillary hair. The Tanner breast stages are as follows (8):
Stage 1: Pre-adolescent; elevation of papilla only.
Stage 2: Breast bud stage; elevation of breast and papilla as a small mound, enlargement of areola diameter.
Stage 3: Further enlargement of breast and areola, with no separation of their contours.
Stage 4: Projection of areola and papilla to form a secondary mound above the level of the breast.
Stage 5: Mature stage; projection of papilla only, due to recession of the areola to the general contour of the breast.
Flexibility was measured by orthopedist author NJK using Nicholas' six flexibility tests. (28) These consisted of elbow hyperextension, external arm rotation, lotus position, external hip rotation (first position for ballet dancers), knee recurvatum, and palms to floor. Measurements were made with a standard goniometer for elbow hyperextension, external arm rotation, first position, and knee recurvatum. Points were given for each measurement in the method of Sapega and colleagues, (29) as seen in Table 1. Elbow hyperextension, external arm rotation, knee recurvatum, and palms to floor measurements were graded on a scale of zero to three. The lotus position was scored as either successful (1) or unsuccessful (0). External hip rotation was measured in degrees as demonstrated by the long axis of each foot.
Range of Motion A standard goniometer was used for 22 measurements of passive range of motion of the lower extremity: hip external rotation and internal rotation (prone), hip flexion (supine) and extension (prone), hip abduction (supine), knee flexion and extension, ankle dorsiflexion with knee in flexion (plie) and extension, ankle plantar flexion with knee in flexion and extension. (30) Active straight leg raise with knee in extension (supine) was also measured. All these measurements were taken by trained physical therapists.
Percent body fat, height, weight, and sexual maturity in the dancer and non-dancer groups were compared using t-tests with a Bonferroni correction. Based on an experiment-wise error of p < 0.05 and 35 comparisons, significance was set at p < 0.01 for each t-test.
For both the dancer (D) and non-dancer (ND) groups, ages ranged from eight to thirteen years with a mean of 10.4 years. Age, height (cm), mass (kg), calculated BMI (kg/[m.sup.2], and percent body fat (%) averages for the two groups are presented in Table 2. Ranges are as follows in height (cm): 122.6 to 165.1 (D) and 119. (4) to 165.1 (ND); mass (kg): 19.5 to 45.4 (D) and 22.2 to 65.3 (ND); BMI (kg/[m.sup.2]): 12.0 to 17.8 (D) and 14.0 to 32.0 (ND); and percent body fat (%): 6.4 to 24.9 (D) and 11.7 to 37. (7) (ND). Significant differences were found between the dancers and non-dancers in mass, BMI, and percentage body fat (BIA), but not in height. Based on the Center for Disease Control Growth Charts, (31) nine out of 43 non-dancers were over the 95th percentile for BMI, and two more were between the 85th and 95th percentile. All of the dancers were under the 85th percentile. Nine dancers and one non-dancer were below the 5th percentile and considered underweight.
The dancer group reported a much higher level of activity than the non-dancers. The dancers had an average of 6.69 [+ or -] 2.49 (range: 4.5 to 12) hours of ballet per week (n = 43), which is the equivalent of at least three 1.5 hours classes per week. Furthermore, 14 of the dancers reported an additional 2.91 [+ or -] 2.94 hours per week of other physical activity. In contrast, the non-dancer group (41 out of 43 answered this question) reported 4.93 [+ or -] 2.51 hours of physical activity on average per week. On average, the dancers began training at the age of 4.24 [+ or -] 1.49 years (range: 2 to 9 years). All of the dancers had been taking two or more classes per week for more than a year at the time of the study.
The non-dancer group was sexually more mature than the dancer group, as shown by a significant difference in average Tanner pubertal stage scores: 1.44 [+ or -] 0.50 for the dancers versus 1.95 [+ or -] 0.75 for the non-dancers (p < 0.0004). The distribution of Tanner scores among the dancers and non-dancers can be seen in Figure 1. Five of the 43 non-dancers had reached menarche, and were an average of 8.4 [+ or -] 4.7 months post-menarche, whereas none of the ballet dancers had menstruated. Of the five non-dancers who had reached menarche, four were at a Tanner stage of 3 and one was at a Tanner stage of 2 at the time of the study. It is estimated that these five non-dancers experienced menarche between the ages of 10.5 and 11.5 years.
[FIGURE 1 OMITTED]
On average, the dancer group scored higher on all six of Nicholas' flexibility tests (Table 3). In four of the tests, there were significant differences (p < 0.0001) between the dancer and non-dancer groups: external arm rotation, the lotus position, external hip rotation, and palms to floor. There was no significant difference between the two groups in elbow hyperextension (p < 0.2506) and knee recurvatum (p < 0.1287).
The dancers were significantly more flexible than the non-dancers in 20 out of the 24 range of motion measurements taken with the standard goniometer (p < 0.005). There was no significant difference between the two groups in the other four standard goniometer measurements: hip internal rotation on the right and left sides (p < 0.9287, 0.7770), and knee extension on the right and left sides (p < 0.0435, 0.0172). The averages for joint range of motion measurements are presented in Table 4.
While many studies have investigated adolescent and adult ballet dancers, very few have looked at the effects of dance training on children. Our study shows that there are several significant differences between ballet students and non-dancers aged 8 to 13 that can be grouped into four areas: weight and body composition, sexual maturity, flexibility, and joint range of motion.
Weight and Body Composition
There were no significant differences in height between the dancer and non-dancer groups. This indicates that growth was similar for dancers and non-dancers, and not slowed in the dancers as reported in the study by Pigeon and colleagues. (18) While ages and heights were similar among the two groups, the non-dancers weighed significantly more and had a higher percent body fat according to the bioelectrical impedance analysis data. The dancers in our study had a lower percent body fat (13.3 [+ or -] 5.0 %) than the dancers of Hergenroeder and associates (32) (20.1 [+ or -] 3.6 %); Hergenroeder and associates obtained their data by total body electrical conductivity, which is another electrical conductivity measurement method that estimates body composition. The difference between the two studies in percent body fat may be due to the fact that the dancers in their study were older (mean age 15.0 [+ or -] 2.0 years).
While body mass index (BMI) is calculated from height and mass and not measured directly like skinfold and bioelectrical impedance data, BMI is the standard measure for monitoring obesity in a population, and is preferred over the skinfold method. (3,33,34) Children are considered overweight if they are over the 95th percentile on gender specific growth charts, and at risk for being overweight if between the 85th and 95th percentile. (3,33,34) Incidence of overweight status among children in the United States has increased dramatically over the past forty years for girls aged 6 to 11 years: 4.5% of the population was obese in the period from 1963 to 1965, whereas in the period from 1999 to 2000 it has been reported that 14.5% of girls can be classified as obese. (35)
We found that over one-fourth of the non-dancer children were considered overweight or at risk of being overweight, whereas none of the dancers were above the 85th percentile. Our BMI average for the dancers (15.2 [+ or -] 1.5) was similar to other studies: Bennell and coworkers (26) reported 16.3 [+ or -] 2.1 for dancers aged 9.6 [+ or -] 0.8 years, and Pigeon and colleagues, 18 in France, reported 15.1 and 14.2 for 11 year old dancers. The BMI average for our non-dancers (19.6 [+ or -] 4.4) was a bit higher than the BMI for controls reported by Bennell and coworkers (18.3 [+ or -] 3.2) and Pigeon and colleagues (17.0).
Not surprisingly, the leaner dancer group was more active than the non-dancer controls. We found that our dancers had an average of 6.7 [+ or -] 2.5 hours of ballet per week (range: 4.5 to 12 hours), which was consistent with Warren's (19) figure of 7.3 [+ or -] 2.2 hours per week for dancers aged 10 to 11 years. In the current study, 14 dancers also had an additional 2.9 [+ or -] 2.9 hours of other activity on average. In contrast, the non-dancer group reported 4.9 [+ or -] 2.5 hours per week of physical activity on average. It is surprising that the non-dancer group reported such a high level of activity when so many of the subjects were considered overweight. However, it has been documented that self-reported activity data are rarely accurate. (36) Since ballet classes are extremely consistent in time and place, and absences from class are highly discouraged, the self-reported activity level for ballet activity may have been more accurate than the data for other physical activity reported by both dancers and non-dancers.
Even among our young children, we found that pubertal development was delayed among the dancers in comparison to the non-dancers, just as Pigeon and colleagues (18) found in their older dancers. The non-dancers had a significantly higher Tanner stage (average: 1.95 [+ or -] 0.75) than the dancers (average: 1.44 [+ or -] 0.50). Such a delay suggests that dancers do not match the trend reported in the United States of children developing pubertal characteristics at earlier ages. (4,6,7) The dancer and non-dancer groups may have had significantly different Tanner stages because so many of the non-dancers were overweight. In 2002, Wang, (37) in a study of 1,501 girls aged 8 to 14 years, and, in 2003, Anderson and coworkers, (6) in a study of national surveys, conclude that there is a close association between early sexual maturation and obesity in girls. It is likely that the results of our study reflect delayed pubertal progression among the dancers and early onset of pubertal characteristics among several of the non-dancers.
Menarche usually occurs at Tanner stage 3 or 4. (8) Whereas all the dancers were at Tanner stage 1 or 2 and none had reached menarche, 10 non-dancers were at Tanner stage 3 and five had menstruated. Several studies have shown that dancers experience a high incidence of delayed menarche, amenorrhea, and irregular menstruation. (15-20) Hamilton and colleagues (16) and Warren and associates (20) showed a strong correlation between delayed menarche and scoliosis. Warren and associates and Kadel and coworkers (17) showed that delayed menarche (age 14 years or older) as well as secondary amenorrhea and intense dance training can place dancers at an increased risk for stress fractures. We were unable to determine incidence of delayed menarche or injury because our subjects were too young, and we did not collect injury data.
It is initially surprising that greater flexibility is evident among such young dancers, aged 8 to 13. However, several of the flexibility tests are directly influenced by dance training, such as palms to floor, (13) the lotus position, and external hip rotation. The two tests where the dancers were not significantly more flexible than the non-dancers were elbow hyperextension and knee recurvatum, both of which are indicators of hypermobility. Our findings support the reports by Klemp and Learmonth (13) and Hamilton and colleagues, (16) which demonstrated that dancers are flexible but not hypermobile.
Joint Range of Motion
The dancers were significantly more flexible in 20 out of 24 of the range of motion measurements of the hip, knee, and ankle. Flexible hips, knees, and ankles are necessary for ballet success and may influence selection bias even in this young age group. The dancers were not significantly more flexible than the non-dancers in knee extension. Knee extension is similar to knee recurvatum, whereby an elevated range of motion indicates hypermobility. There was no significant difference between the dancers and non-dancers in hip internal rotation, however the dancers had significantly greater external hip rotation. This may be due to the exclusive emphasis on turning out from the hip during ballet movements; internal hip rotation is very rarely utilized or stretched by ballet dancers. In a 1999 study, Bennell and associates (25) also found that control non-dancers had greater active hip internal rotation than the dancers in their study. However, Bennell and associates found that the non-dancers had greater active hip external rotation than the dancers, but passive range of motion was not measured. Our hip range of motion measurements were consistent with the results in the study by Hamilton and coworkers (16) who found greater external rotation but lesser internal rotation among adult dancers when compared with non-dancer controls.
We found that characteristics associated with professional ballet dancers, such as flexibility and increased joint range of motion, can be seen in dancers as young as eight to thirteen years old, which supports the findings of earlier studies. We also determined that ballet students are leaner and sexually immature in comparison with non-dancers. Many of the non-dancer children in our study were overweight which, combined with a low activity level, may predispose them to future health problems such as diabetes and obesity. Future longitudinal studies are needed to evaluate the effects of sexual immaturity among ballet students.
We would like to thank the dancers and staff at the Boston Ballet School and the Physical Therapy department at Boston Children's Hospital. We give further thanks to Phuong Dang, Jerry Larson, and Michael Orendurff for statistical analysis, and to Rachel Kadel for her assistance in this study.
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Nancy J. Kadel, M.D., is in the Department of Orthopaedics and Sports Medicine, University of Washington, Seattle, Washington. Emily A. Donaldson-Fletcher, B.A., is a medical student at Tulane University, New Orleans, Louisiana. Lynda F. Gerberg, M.D., is in the Department of General Pediatrics, Schneider Children's Hospital, Long Island Jewish Medical Center, New Hyde Park, New York. Lyle J. Micheli, M.D., is in the Division of Sports Medicine, Children's Hospital, Boston, Massachusetts.
Correspondence: Nancy J. Kadel, M.D., Department of Orthopaedics and Sports Medicine, University of Washington, 1959 NE Pacific, Box 356500, Seattle, Washington 98915.
Table 1 Grading Criteria for Nicholas' Six Flexibility Tests Flexibility Test Grade Criteria Elbow hyperextension 0 Less than 180[degrees] of elbow extension 1 180[degrees]-189[degrees] of elbow extension 2 190[degrees]-199[degrees] of elbow extension 3 Greater than 199[degrees] of elbow extension External arm rotation 0 Plane of palm cannot reach horizontal 1 Plane of palm 0[degrees]-30[degrees] beyond horizontal 2 Plane of palm 31[degrees]-60[degrees] beyond horizontal 3 Greater than 60[degrees] beyond horizontal Lotus position 0 Cannot assume proper position 1 Can assume proper position External hip rotation Degrees The maximum number of degrees of (first position) rotation demonstrated by the long axis of each foot Knee recurvatum 0 Less than 180[degrees] of knee extension 1 180[degrees]-189[degrees] of knee extension 2 190[degrees]-199[degrees] of knee extension 3 Greater than 199[degrees] of knee extension Palms to floor 0 Cannot touch floor 1 Can touch floor with at least one finger 2 Can touch metacarpal heads to floor 3 Can touch palm flat to floor (Sapega AA, Minkoff J, Valsamis M, et al: Musculoskeletal performance testing and profiling of elite competitive fencers. Clinics in Sports Medicine 3(1):231-244, 1984.) Table 2 Body Composition and Anthropometric Measurements of Dancer (n = 43) and Non-Dancer Children (n = 43), Mean [+ or -] SD Age (years) Height (cm) Dancers 10.4 [+ or -] 1.2 140.7 [+ or -] 9.7 Non-dancers 10.4 [+ or -] 1.4 144.3 [+ or -] 11.4 Mass (kg) BMI (kg/[m.sup.2]) Dancers 30.4 [+ or -] 5.5 * 15.2 [+ or -] 1.5 * Non-dancers 41.6 [+ or -] 13.3 19.6 [+ or -] 4.4 Percent Body Fat (BIA) Dancers 13.3 [+ or -] 5.0 * Non-dancers 20.7 [+ or -] 6.7 * significant difference from non-dancers (p < 0.0001) Table 3 Flexibility Measurements of Dancer and Non-Dancer Children (Mean [+ or -] SD) Measurement Dancers (n = 43) Non-Dancers (n = 43) Elbow hyperextension 1.47 [+ or -] 0.70 1.30 [+ or -] 0.60 External arm rotation 2.02 [+ or -] 0.67 * 1.21 [+ or -] 0.56 Lotus position 0.93 [+ or -] 0.26 * 0.49 [+ or -] 0.51 External hip rotation 174.09 [+ or -] 4.65 * 167.79 [+ or -] 9.13 (degrees) Knee recurvatum 1.05 [+ or -] 0.49 0.88 [+ or -] 0.50 Palms to floor 2.72 [+ or -] 0.63 * 1.14 [+ or -] 0.89 * significant difference from non-dancers (p < 0.0001) Table 4 Joint Range of Motion Measurements Right (R) and Left (L) in Degrees (Average [+ or -] SD) Among Dancer (n = 43) and Non-Dancer Children (n = 43) Measurement Dancers Hip flexion L 139.91 [+ or -] 7.90 ([dagger]) Hip flexion R 139.33 [+ or -] 7.73 ([dagger]) Hip extension L 19.81 [+ or -] 12.29 * Hip extension R 20.72 [+ or -] 12.86 ([dagger]) Hip internal rotation L 48.58 [+ or -] 9.04 Hip internal rotation R 48.51 [+ or -] 7.87 Hip external rotation L 48.56 [+ or -] 9.89 ([dagger]) Hip external rotation R 48.86 [+ or -] 9.95 * Hip abduction L 47.70 [+ or -] 8.04 ([dagger]) Hip abduction R 45.70 [+ or -] 7.49 ([dagger]) Straight leg raise L 110.09 [+ or -] 11.58 ([dagger]) Straight leg raise R 107.63 [+ or -] 13.96 ([dagger]) Knee extension L 3.93 [+ or -] 3.57 Knee extension R 3.63 [+ or -] 3.11 Knee flexion L 145.42 [+ or -] 7.63 ([dagger]) Knee flexion R 146.02 [+ or -] 6.71 ([dagger]) Ankle dorsiflexion with straight 7.91 [+ or -] 4.82 * leg L Ankle dorsiflexion with straight 8.47 [+ or -] 4.36 * leg R Ankle plantar flexion with straight 58.86 [+ or -] 4.57 ([dagger]) leg L Ankle plantar flexion with straight 56.61 [+ or -] 4.87 ([dagger]) leg R Ankle dorsiflexion with bent leg L 16.98 [+ or -] 5.20 ([dagger]) Ankle dorsiflexion with bent leg R 17.33 [+ or -] 6.32 ([dagger]) Ankle plantar flexion with bent 60.65 [+ or -] 5.86 ([dagger]) leg L Ankle plantar flexion with bent 60.21 [+ or -] 6.29 ([dagger]) leg R Measurement Non-Dancers Hip flexion L 125.28 [+ or -] 11.82 Hip flexion R 123.91 [+ or -] 11.39 Hip extension L 11.74 [+ or -] 5.16 Hip extension R 10.91 [+ or -] 5.42 Hip internal rotation L 48.02 [+ or -] 9.18 Hip internal rotation R 48.65 [+ or -] 6.48 Hip external rotation L 40.65 [+ or -] 8.04 Hip external rotation R 41.84 [+ or -] 8.08 Hip abduction L 35.35 [+ or -] 5.22 Hip abduction R 35.26 [+ or -] 5.74 Straight leg raise L 70.02 [+ or -] 8.40 Straight leg raise R 68.65 [+ or -] 8.83 Knee extension L 2.61 [+ or -] 2.29 Knee extension R 2.16 [+ or -] 2.44 Knee flexion L 134.28 [+ or -] 7.76 Knee flexion R 132.86 [+ or -] 7.38 Ankle dorsiflexion with straight 4.54 [+ or -] 3.38 leg L Ankle dorsiflexion with straight 4.09 [+ or -] 8.65 leg R Ankle plantar flexion with straight 45.88 [+ or -] 8.31 leg L Ankle plantar flexion with straight 46.98 [+ or -] 6.12 leg R Ankle dorsiflexion with bent leg L 10.12 [+ or -] 4.76 Ankle dorsiflexion with bent leg R 10.54 [+ or -] 5.05 Ankle plantar flexion with bent 53.70 [+ or -] 4.58 leg L Ankle plantar flexion with bent 52.74 [+ or -] 4.78 leg R * significant difference from non-dancers (p < 0.005); ([dagger]) significant difference from non-dancers (p < 0.0001)
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|Author:||Kadel, Nancy J.; Donaldson-Fletcher, Emily A.; Gerberg, Lynda F.; Micheli, Lyle J.|
|Publication:||Journal of Dance Medicine & Science|
|Date:||Jul 1, 2005|
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