Evaluating Shoulder Rotation Strength Asymmetry in Elite Wheelchair Basketball and Sitting Volleyball Players

Abstract

Background. Although an imbalanced strength profile is considered a risk factor for injury, research on asymmetry in para-athletes is limited. Objective. This study investigated the potential unilateral and bilateral asymmetries of the glenohumeral muscles in elite male players of sitting volleyball (SV) and wheelchair basketball (WB). Methods. Twenty-two elite SV and WB players (each group of 11 players) participated in this study. A Biodex dynamometer was used to measure the internal and external rotator of the glenohumeral muscle strength at 60°/s velocity in a concentric/concentric mode. Results. Findings indicated that both groups exhibited bilateral strength asymmetries in internal rotation and external rotation. The SV players had higher inter-limb asymmetric values than WB players regarding IR movement. The study also revealed a unilateral ratio imbalance among the SV players (ER/IR ratio mean = 88.80, SD = 18.70 for dominant and mean = 79.45, SD = 14.65 for non-dominant). They had a significantly greater ER/IR ratio than the WB players (p = 0.016) and also a significant dominant side × group interaction effect (p = 0.049). The WB group had stronger IR muscles relative to their body weight comparing the SV group (p = 0.018, partial eta-squared = 0.248, large effect). Conclusions. Participants demonstrated an asymmetrical rotational strength profile with IR strength dominance. Although this muscle imbalance has been considered a shoulder injury risk factor among overhead athletes, it may not apply to para-athletes due to their functional adaptation requirements. Therefore, specific asymmetry thresholds need to be explored among them.