Shoulder external/internal rotation peak torques ratio side-asymmetry, mean work and power ratios balance worsening due to different fatigue resistance of the rotator muscles in male handball players

Introduction: Fatigue could worsen shoulder cuff rotator balance if fatigue of the external rotation (ER) could appear faster in comparison with the internal rotation (IR). The shoulder rotation peak torques (τmax) side-asymmetry and muscle endurance effect on the mean work (W), mean power (P) and their ratio of ER/IR in handball players was investigated. Methods: Eighteen semi-professional male handball players participated. The tests were performed using an isokinetic dynamometer by the shoulder isokinetic internal-external rotation movements at angular velocities of 60°/s, 240°/s via concentric contractions. The W, P were determined and their ratios of the ER/IR were calculated for the first ten and last ten repetitions of the movements at 240°/s. Results: Muscle side asymmetry in Tmax, W, P was not observed at 240°/s. The W, P of the ER and ratios of the ER/IR (WER/WIR=0.76 (dominant D), 0.74 (non-dominant N) arm; PER/PIR=0.68 D, 0.70 N) in the last ten repetitions were significantly lower than those (WER/WIR=0.80 D, 0.79 N; PER/PIR=0.78 D, 0.77 N) in the first ten movements. Conclusion: Fatigue resistance of the ER was lower than that of the IR. Therefore, the ER/IR ratios of W, P decrease due to repeated rotation movements. Level of evidence: IIIa.