Context: Shoulder pain is the main cause of missed or modified training in competitive swimmers. Shoulder musculoskeletal maladaptations occur to some extent as a consequence of training loads during swimming that may increase the risk of shoulder injury. Further evidence is needed to understand the training intensities at which these maladaptations occur. Objective: To determine the acute effect of training intensity on the shoulder musculoskeletal physical qualities associated with shoulder injury in competitive swimmers. Design: Cross-sectional study. Setting: Indoor swimming pool. Patients or Other Participants: Sixteen asymptomatic national- and regional-level swimmers (7 females, 9 males; age = 14.6 ± 3.9 years, height = 160.5 ± 12.7 cm, mass = 55.3 ± 12.5 kg). Main Outcome Measure(s): Bilateral active shoulder-rotation range of motion (ROM), joint position sense, latissimus dorsi length, combined elevation test, and shoulder-rotation isometric peak torque and handgrip peak force normalized to body weight were measured before and immediately after low- and high-intensity swim-training sessions. The intensity of the sessions was determined by the distance swum over or at the pace threshold and confirmed by the swimmer's rating of perceived exertion. Results: After the high-intensity training session, shoulder external-rotation ROM (dominant side: P < .001, change = -7.8°; d = 1.10; nondominant side: P = .002, change = -6.5°, d = 1.02), internal-rotator isometric peak torque (dominant side: P < .001, change = -11.4%, d = 0.42; nondominant side: P = .03, change = -6.6%, d = 0.20), and external-rotator isometric peak torque (dominant side: P = .004, change = -8.7%, d = 0.27; nondominant side: P = .02, change = -7.6%, d = 0.25) were reduced. No changes were found in any of the outcome measures after the low-intensity session. Conclusions: Shoulder active external-rotation ROM and rotation isometric peak torque were decreased immediately after a high-intensity training session, possibly increasing the risk of injury during subsequent training. Monitoring these variables may help practitioners adjust and manage training loads to decrease the risk of shoulder injury.
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