Therapeutic Exercise for Shoulder Complex Function - Effects on essential biomechanical and neurophysiological parameters

Abstract

Introduction: Shoulder pain is a major musculoskeletal complaint. Among different contributions factors, the scapular adaptations have been considered relevant. However, there are conflicting findings regarding the association between scapular adaptations and chronic shoulder pain, and the effectiveness of therapeutic exercise. Main objective: To determine the biomechanical and neurophysiological parameters essential for characterizing participants with chronic shoulder pain and to measure the respective changes after a scapular-based therapeutic exercises program. Methods: Four research studies, 3 cross-sectional and one pre-post single group design, involving a total of 108 subjects with and without chronic shoulder pain, and three review studies were performed. Symptomatic subjects were characterized, taking as reference asymptomatic subjects, in outcomes as: a) scapular muscle stiffness (study II); b) trapezius' Hoffmann reflex (study III); c) scapular electromyographic activity level and ratios and kinematics (study IV). To measure changes after a scapular-based exercises program, participants of study VII were assessed in scapular and self-reported outcomes at pre- and post-intervention. The effectiveness of scapular therapeutic exercises was assessed by a systematic review with meta-analysis, and two narrative reviews explore myotonometry and an intervention algorithm to select scapular therapeutic exercises based on clinical assessment. Results: Chronic shoulder pain is associated to changes in: a) trapezius's muscle stiffness (study I-II); b) amplitude or latency of Hoffmann reflex of trapezius (study III); c) scapular muscular activity level and ratios and scapular motion (study IV). A scapular therapeutic exercises program based on the percentage of muscle activity (study VI), led to changes in shoulder function (study V, VII), pain and in scapular outcomes (study VII). Conclusions: Chronic shoulder pain is associated to changes in trapezius muscle stiffness and Hoffmann reflex, and in scapular muscular activity, ratios and motion, that can be modified by a scapular therapeutic exercises.