Effect of fatigue and sex on isokinetic torque values in water polo athletes

BACKGROUND: Water polo is an Olympic sport that combines the rigors of swimming and throwing while being defended by an opponent. Shoulder injuries linked to the repetitive movements of throwing and swimming are very common, especially for females. The purpose of this study was to determine the effect of sex and fatigue on shoulder torque values and muscle balance ratios. METHODS: Twenty-four water polo players (13 females, 11 males) were recruited from a Division III school in Southern California and performed shoulder external and internal rotation and abduction and adduction strength testing using an isokinetic dynamometer (120 degrees/s). Thirty repetitions were performed, and the mean peak torque was computed for the first five and last five repetitions by averaging the three largest torque values. Fatigue ratios were computed by dividing the mean peak torque from the last five repetitions by the mean peak torque from the first five repetitions. RESULTS: Females had significantly smaller mean peak torque values, both raw and normalized for body mass, than males. The ratio of external rotation to internal rotation mean peak torque values was affected by both sex and fatigue while the ratio of abduction and adduction values was not. The abduction fatigue ratio differed between sexes. CONCLUSIONS: When compared to females, male subjects had much greater internal rotation strength which led to a greater imbalance of their shoulder rotation torque ratio. This strength difference may explain the increased incidence of female shoulder injuries. Adduction strength may differentiate elite-level players from lower-level players.