Unilateral Breathing in Elite Swimmers: Association With Glenohumeral Microinstability and Periscapular Fatigue.

BACKGROUND: Swimmer's shoulder is a highly prevalent, multifactorial overuse condition in competitive athletes, often involving glenohumeral microinstability, scapular dyskinesis, and muscular imbalance. Repetitive unilateral breathing patterns may create a substantial asymmetrical load, exacerbating early periscapular fatigue and contributing to symptomatic instability on the breathing side. HYPOTHESIS: A targeted 8-week rehabilitation protocol focusing on periscapular control and rotator cuff rebalancing will result in a significant and sustained reduction in pain and improved strength symmetry in hyperlax elite swimmers presenting with shoulder pain on the breathing side. STUDY DESIGN: Retrospective monocentric cohort study. LEVEL OF EVIDENCE: Level 3. METHODS: A total of 14 elite swimmers (Beighton ≥5 out of 9) with shoulder pain on the breathing side and negative magnetic resonance imaging scan for acute lesions were enrolled. Maximal voluntary isometric contraction (MVIC) strength of the upper trapezius (UT), middle trapezius (MT), and lower trapezius (LT), internal rotators (IRs), and external rotators (ERs) was measured using a handheld dynamometer at 1- and 2-year follow-up (1FU and 2FU) after an 8-week rehabilitation program. Pre- to post-treatment changes were assessed using paired Student's t tests. RESULTS: At 2FU, statistically significant and clinically relevant strength gains were observed in the MT (+24.9%; P = 0.002), LT (+53.6%; P = 0.001), IRs (+66.7%; P < 0.001), and ERs (+100.0%; P < 0.001). Mean visual analog scale pain scores decreased from 3.7 ± 1.0 at baseline to 0.85 ± 0.5 at final follow-up, corresponding to an 87.8% reduction (P < 0.001), indicating a durable restoration of functional shoulder balance. CONCLUSION: An individualized, asymmetry-aware rehabilitation program focusing on MT/LT reactivation and balanced IR/ER strengthening yields highly significant and durable functional gains and pain relief in hyperlax elite swimmers. The strength profile suggests a favorable shift away from compensatory UT activation toward optimal scapular stabilization. CLINICAL RELEVANCE: Targeted scapular (MT/LT) reactivation and balanced rotator cuff rebalancing effectively reduce pain and restore functional symmetry in hyperlax elite swimmers presenting with unilateral breathing-induced microinstability.