Research Information System
Clinical Biomechanics, vol.137, 2026 (SCI-Expanded, Scopus)
Background: Alterations in shoulder muscle thickness and strength are believed to be associated with rotator cuff (RC) tendinopathy. Previous studies have mainly focused on measuring the supraspinatus tendon thickness in relevant patients with shoulder pain. This study examined differences in shoulder muscle thickness and RC strength in the symptomatic and asymptomatic shoulders of patients with RC tendinopathy. Methods: Thirty-five patients with unilateral RC tendinopathy were included in this study. Muscle thickness of the supraspinatus, infraspinatus, deltoid, and combined middle trapezius+rhomboid was measured via ultrasonography, while RC strength (internal rotator [IR] and external rotator [ER]) at 60°/s and 180°/s was assessed using an isokinetic device. Findings: No significant differences were found in muscle thickness (supraspinatus p = .342; infraspinatus, p = .746; deltoid p = .112; middle trapezius+rhomboid, p = .378), RC strength (ER 60°/s p = .283; IR 60°/s p = .337; ER 180°/s p = .334; IR 180°/s p = .141), or ER/IR strength ratios (60°/s p = .857; 180°/s p = .379) between symptomatic and asymptomatic shoulders. Significant correlations ranging from weak-to-high were found between supraspinatus, infraspinatus, and deltoid thickness and RC strength (r = 0.354–0.732, p < .05). A moderate correlation was observed between middle trapezius+rhomboid thickness and shoulder ER strength (r = 0.620–0.625, p < .001), but no correlation with IR strength (p > .05). Interpretation: Patients with RC tendinopathy exhibited similar shoulder muscle thickness, ER and IR strength, and ER/IR strength ratios between symptomatic vs. asymptomatic shoulders. Additionally, shoulder muscle thickness appears to be associated with shoulder rotator strength.