Rotator Cuff Muscle-Tendon Properties Are Heterogeneously Affected By Exercise In Young Swimmers With Supraspinatus Tendinopathy

Highly repetitive overhead loading and a high volume of training may lead to permanent overloading, overdose, and, consequently, adaptation of the shoulder’s musculoskeletal complex. PURPOSE: To investigate the acute effects of fatigue loading after isokinetic exercise on the spatial distribution of shoulder girdle tendon and muscle stiffness in swimmers with supraspinatus tendinopathy. METHODS: A group of national-level adolescent swimmers (n = 32, age 18.2 ± 1.0 years) participated in this study. Participants were divided into two groups: swimmers with supraspinatus tendinopathy and current pain sensations (n = 16) and swimmers matched with the control group (n = 16). Stiffness of the shoulder girdle tendon (supraspinatus, SST) and muscles (supraspinatus, SSM; infraspinatus, INF) was measured using shear-wave elastography (SWE). The fatigue-induced exercise was performed on an isokinetic dynamometer in the prone position. The dynamometer was set to perform a repeated shoulder flexion-extension isokinetic exercise (eight sets of 60 repetitions, with one minute of rest) at an isokinetic speed of 180o/s. The outcome measures were obtained at two time points: baseline and immediately post-exercise. For data analysis, each structure was divided into three segments: proximal (in relation to the insertion), middle, and distal. A three-way RM-ANOVA, considering Time (baseline-immediately post), Group (shoulder pain-control matched), and Segment (proximal-middle-distal), was used for SWE outcomes. RESULTS: The SST, SSM, and INF stiffness were significantly greater in swimmers with supraspinatus tendinopathy compared to the control-matched group (p ≤ 0.001). Moreover, SST stiffness was greater immediately post-exercise in the middle segment compared to stiffness at baseline, and the proximal and distal segments (p ≤ 0.001). For SSM, the spatial distribution of stiffness was greater in the distal segment compared to stiffness in other segments (p ≤ 0.001), while in INF, stiffness was greater in the middle segment compared to stiffness in other segments (p = 0.001). CONCLUSIONS: The stiffness of the rotator cuff tendon and muscles showed a heterogeneous spatial distribution in response to fatigue-induced exercise in swimmers with supraspinatus tendinopathy. The Polish-U.S. Fulbright Commission (Fulbright Senior Award 2023-24)