Shoulder tensiomyography and isometric strength in swimmers before and after a fatiguing protocol

Context. Shoulder muscles are active during front crawl swimming to provide propulsion and stabilize the glenohumeral and scapulothoracic joints. It has been proposed that fatigue might contribute to altered activation of these muscles and represent a risk factor for injuries. Tensiomyography (TMG) might represent a non-invasive tool to detect exercise-induced neuromuscular fatigue changes in contractile parameters of the skeletal muscles, and it has never been used in the shoulder muscles in swimmers. Objective. The aim of this study was to assess the effects of a fatiguing swimming protocol on shoulder muscles TMG parameters and isometric strength in competitive swimmers. Design. A cross-sectional study. Setting. A swimming pool facility. Patients or Other Participants. Sixteen young front crawl competitive swimmers were invited to participate in the study, and 14 of them (21 y, range 17-26, 11 males 3 females) completed all the assessments before and after a 30-min high-intensity swimming training. Main Outcome Measure(s). The main outcome included the TMG assessment which was performed on seven muscles of the shoulder according to front crawl biomechanics and applicability of the technique, in order to obtain data such as time to contraction and muscle belly radial displacement (Dm), whereas isometric strength was assessed with a digital dynamometer during shoulder flexion, extension, external rotation and internal rotation. Results. Fatigue induced a smaller Dm (-0.5 mm, 95% CI: -0.7 - -0.3, p< 0.001, pη2= 0.692), mostly observable in latissimus dorsi and pectoralis major muscles. Only shoulder extension showed a significant isometric strength reduction after the fatiguing protocol (-0.03 N/kg, 95% CI: -0.05 - -0.01, p= 0.045, pη2= 0.275). Conclusions. This study provides preliminary evidence for the usefulness of TMG to detect fatigue-induced changes in contractile properties of the shoulder muscles in swimmers, in particular the latissimus dorsi, pectoralis major and lower trapezius.