Ultrasound-Based Assessment of Shoulder Soft Tissue Alterations in Young Adults Performing Upper Limb Weight Training: A Cross-Sectional Study

Abstract

Abstract Background: The subacromial space, measured as the acromiohumeral distance (AHD), is a key determinant of shoulder biomechanics and injury risk. Athletes performing repeti- tive upper-limb resistance training are particularly exposed to cumulative tendon stress. Musculoskeletal ultrasound (US) enables dynamic, cost-effective assessment, yet its role in strength athletes remains underexplored. The aim of this study was to determine whether young adults engaged in regular upper-limb weight training present a narrower acromio- humeral distance and a higher prevalence of ultrasound-detected tendon abnormalities compared with non-weight-training individuals. Methods: We conducted a post hoc sub- analysis of a cross-sectional cohort of 66 young adults (18–45 years; mean 29.6 ± 9.0 years; 27 men/39 women) evaluated with standardized shoulder US. Participants were classified as weight-training (n = 15; 36.2 ± 5.7 years; 11 men/4 women) or non-weight-training (n = 51; 27.6 ± 8.8 years; 16 men/35 women). AHD was measured in millimeters, and abnor- malities of the supraspinatus, subscapularis, long head of the biceps tendon (LHBT), and subacromial–subdeltoid bursa were recorded. Between-group comparisons used Welch’s t-test or ω2/Fisher’s exact test; effect sizes were expressed as Cohen’s d or odds ratios (OR). Multiple testing was corrected with the false discovery rate (FDR). Results: Weight- training participants exhibited a significantly smaller AHD (7.13 ± 0.54 vs. 7.49 ± 0.68 mm; t (28) = →2.12, p = 0.038; mean difference →0.36 mm, 95% CI →0.70 to →0.03; Cohen’s d = →0.56). Supraspinatus tendinopathy was more prevalent in weight-training athletes (93.3% vs. 41.2%; OR 17.7, 95% CI 2.16–145.8; FDR-adjusted p = 0.003). Subscapularis ten- dinitis (40.0% vs. 17.6%; OR 3.58, 95% CI 1.00–12.88; FDR p = 0.14) and LHBT tenosynovitis (20.0% vs. 3.9%; OR 6.82, 95% CI 1.02–45.8; FDR p = 0.09) showed non-significant trends. Conclusions: Upper-limb weight training in young adults is associated with reduced AHD and a markedly higher prevalence of supraspinatus tendinopathy. Ultrasound proved valuable for early detection of structural and morphological alterations in shoulder soft tis- sues. Preventive strategies focusing on load management, exercise technique, and targeted strengthening should be prioritized.