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2000 Publications

STRENGTH AND FATIGUE IN AMENORRHEIC BALLET DANCERS.by Liederbach M, Kremenic IJ, Glace BW, McHugh MP, Gleim GWNicholas Institute of Sports Medicine and Athletic Trauma and Hospital for Joint Diseases, New York, NY - last modified 2013-02-10 00:00
Medicine and Science in Sports and Exercise. 32: S279, 2000.

 

The incidence of musculoskeletal injuries in ballet dancers is higher in women versus men. Among women a higher incidence of injury is seen in amenorrheic (amen) versus eumenorrheic (eumen) dancers.

The purpose of this study was to compare strength and fatigue between amenorrheic (n=5), eumenorrheic (n=9) and male professional ballet dancers (n=10). The following measurements were made: percent body fat, BMI, isokinetic (60º/s) quadriceps (quad) and hamstring (ham) strength, and EMG activity during isometric quad fatigue tests (50% MVC).

Body fat was lower in men (10%) versus eumen (20%, p<0.001) and amen (16%, p&kt0.05). BMI was lower in amen (18.3) versus eumen (20.2, p<0.05) and men (21.3, p<0.01). Quad strength (N.m/kg) in amen was 68% lower than eumen (p<0.001) and 80% lower than men (p<0.001).

Ham strength (N.m/kg) in amen was 70% lower than eumen (p<0.001) and 83% lower than men (p<0.001). EMG amplitude (RMS) and mean frequency (MF) during quad MVCs were not different between groups (p=0.81, p=0.19). For the fatigue test, time-to-fatigue, RMS slope and MF slope were not different between groups (p=0.59, p=0.91, p=0.24).

These results demonstrate gross quad and ham weakness in amen ballet dancers who are participating fully in professional schedules. RMS and MF during MVCs indicated normal activation and recruitment.

Despite gross weakness in amen dancers, all indices of fatigue were similar between groups. The high incidence of injuries in amenorrheic dancers may be due to inadequate strength to meet the demands of ballet.