Effects of resistance exercises on rotator cuff muscle mechanical characteristics in shoulders with and without rotator cuff tears

RESEARCH ARTICLE Effects of resistance exercises on rotator cuff muscle mechanical characteristics in shoulders with and without rotator cuff tears Andrew J. Nasr Yen-Sheng Lin , Henry Wang * 1 , Jijia Wang3, Michael Khazzam4, Nitin B. Jain5, 2 6,7,8 1 School of Physical Therapy, Texas Woman’s University, Dallas, Texas, United States of America, 2 Department of Neuroscience, Brown University Providence, Rhode Island, United States of America, 3 Department of Applied Clinical Research, UT Southwestern Medical Center, Dallas, Texas, United States of America, 4 Baylor Scott & White, Orthopaedic Associates of Dallas, Complex Shoulder Institute, Grapevine, Texas, United States of America, 5 Department of Physical Medicine and Rehabilitation, University of Michigan, Ann Arbor, Michigan, United States of America, 6 Department of Orthopaedic Surgery, UT Southwestern Medical Center, Dallas, Texas, United States of America, 7 Department of Physical Medicine and Rehabilitation, UT Southwestern Medical Center, Dallas, Texas, United States of America, 8 Graduate Institute of Medical Sciences, National Defense Medical University, Taipei, Taiwan * Abstract OPEN ACCESS Citation: Nasr AJ, Wang H, Wang J, Khazzam M, Jain NB, Lin Y-S (2026) Effects of resistance exercises on rotator cuff muscle mechanical characteristics in shoulders with and without rotator cuff tears. PLoS One 21(5): e0347233. https://doi.org/10.1371/journal.pone.0347233 Editor: Emil George Haritinian, Carol Davila University of Medicine and Pharmacy: Universitatea de Medicina si Farmacie Carol Davila din Bucuresti, ROMANIA Received: September 10, 2025 Accepted: March 30, 2026 Published: May 27, 2026 Copyright: © 2026 Nasr et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data availability statement: All relevant data are within the manuscript and its Supporting Information files. Funding: This research study was supported by the Hoffman Endowment Orthopedic Research Background Rotator cuff tears are the primary cause of shoulder pain, often managed with resistive exercise. Understanding how rotator cuff muscles respond to low-intensity rehabilitation-based exercise is critical for optimizing rehabilitation strategies, yet these responses remain poorly characterized. Methods This study investigated changes in shear wave speed, cross-sectional area, and strength of the supraspinatus and infraspinatus muscles following a 30-repetition isometric contraction protocol at 20% of isometric volitional contraction in shoulders with and without rotator cuff tears. Three-way mixed ANOVAs with repeated measures were performed to evaluate the main effects of tear status, baseline vs post-exercise, passive and active conditions on supraspinatus and infraspinatus as well as the interaction between main effect and cross-sectional area and shear wave speed. Results Twenty participants were assessed using ultrasound imaging pre- and post-exercise. The findings revealed that participants with rotator cuff tears experienced a significant reduction in passive supraspinatus shear wave speed (p = 0.0021), indicative of increased muscle compliance, while asymptomatic participants exhibited no significant change. Cross-sectional area increased significantly post-exercise in both PLOS One | https://doi.org/10.1371/journal.pone.0347233 May 27, 2026 1 / 15 Fund and Research Advisory Committee’s Interdisciplinary Grant, School of Health Professions, UT Southwestern Medical Center. This study is partially supported by Paralyzed Veterans of America Research Foundation #3201 (to Y.S.L.) and Trauma Research and Combat Casualty Care Collaborative Competitive Award #178707 (to Y.S.L.). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: The authors have declared that no competing interests exist. groups under active conditions (asymptomatic group: p = 0.0046 and symptomatic group: p = 0.0020), though no change was observed in rotator cuff tear participants during passive testing (p = 0.8900). Strength assessments showed marked declines in both groups following exercise (p-values <0.005), reflecting peripheral weakness. Conclusion These findings suggest that rotator cuff tears are associated with maladaptive reductions in supraspinatus muscle stiffness during acute exercise, potentially impairing functional capacity and necessitating longer recovery periods. In contrast, asymptomatic participants maintain supraspinatus stiffness despite weakness, underscoring differential adaptation to low-intensity exercise. Introduction Shoulder pain is a common musculoskeletal complaint globally, exhibiting a point prevalence of 26%. [1,2] Around 66.7% of adults are likely to experience shoulder pain at some point in their lives, with rotator cuff tears (RCTs) identified as the primary etiology. [3] An initial trial of non-operative treatment is often recommended, with resisted exercises aimed at improving glenohumeral motion and active scapular retraction, followed by exercises to improve scapular and glenohumeral muscle function, as the preferred intervention based on clinical practice guidelines. [4–6] Resistive exercise has been demonstrated to significantly improve patient outcomes however, the incidence of nonresponse rates remain concerning. [7] This variability in individual response underscores the necessity for a nuanced understanding of the underlying mechanisms contributing to such variability. A recent scoping review examining exercise programs for managing rotator cuff-related pain highlighted considerable variability in the frequency, intensity, time, and type of exercise utilized in randomized controlled trials, emphasizing inconsistency of physical therapy intervention. [8] Rotator cuff disease is multifactorial with recent theoretical models suggesting distinct mechanistic domains as it relates to a patient’s response to resisted exercises. [9] There remains clinical uncertainty in how the rotator cuff muscles respond to submaximal exercise in healthy populations and in patients with RCTs. In healthy populations, muscle cross-sectional area (CSA) increases [10,11], and strength decreases [12,13] following an acute bout of high-intensity exercise (e.g., pitching). However, the acute effects of submaximal exercise on muscle strength and volume in compromised populations are less understood. Much of the existing literature focuses on biomechanical alterations secondary to fatigue, utilizing electromyography studies. Surface electromyography effectively captures muscle activity, however, it is constrained by its inability to isolate specific muscles, often recording signals from adjacent musculature due to intermuscular crosstalk. [14] Shear wave elast (...truncated)