Shoulder girdle muscle function and morphology after isotonic and isokinetic exercise in swimmers with rotator cuff tendinopathy

This study aimed to evaluate the functional and morphological changes following repetitive isotonic and isokinetic overhead exercises in 32 national-level swimmers (16 with rotator cuff (RC) tendinopathy, and 16 asymptomatic controls). Participants completed a randomized crossover test involving isotonic (swim ergometer) and isokinetic (dynamometer) exercise protocols. Outcome measures included pain, shoulder range of motion (ROM), muscle strength, and acromiohumeral distance (AHD) at 0°, 60°, and 90° abduction. Post-exercise, both groups experienced increased pain and significant reductions in ROM, muscle strength and AHD at all angles (all p < 0.001). However, the RC tendinopathy group exhibited consistently smaller AHD and greater declines in ROM and strength, particularly following isokinetic exercise. Isokinetic exercise induced greater immediate changes than isotonic exercise, likely due to continuous force generation throughout the full ROM. However, these findings represent acute responses and should not be interpreted as evidence of impingement risk.