Eccentric and concentric knee extensor muscle performance in professional ballet dancers.

Ballet dancers are exposed to great eccentric loading of the lower extremities due to a high frequency of repetitive jumps and leaps. The purpose of this study was to evaluate eccentric (ECC) and concentric (CON) knee extensor muscle endurance and strength in professional ballet dancers (six men and 11 women) in relation to moderately active control subjects (17 men and 18 women). A Biodex dynamometer was used for isokinetic torque measurements. The ECC endurance (total work per kilogram) was on average 31% greater in professional ballet dancers compared to control subjects, while the corresponding average difference for CON endurance was 7%. A greater ECC CON total work ratio was observed for ballet dancers (mean ballet, 2.07; mean control, 1.74). The ECC and CON strengths (peak torque per kilogram) were greater in professional ballet dancers compared to controls (27 and 22%). No intraindividual torque difference between left and right limbs was found. Men showed significantly greater strength (peak torque per kilogram) and endurance (total work per kilogram) compared to women, similar in both groups. No differences in the ECC/CON relationship between genders were observed. In essence, our results favor the hypothesis that repetitive loading of the lower extremities in ballet dance leads to a higher standard of ECC knee extensor endurance.