Scapular instability and overuse injury in keyboardists

Playing-Related Musculoskeletal Disorders (PRMD) are overuse injuries that affect a large number of musicians. In this study we sought to understand the neurophysiologic mechanisms that predispose musicians to PRMD and investigated the role of scapular instability in symptomatic keyboardists. Nine symptomatic and 16 asymptomatic keyboardists with at least 10 years of playing experience played octaves on a full-size keyboard, while activity from arm muscles and the upper and lower trapezii (scapular stabilizers) were recorded. Electrophysiological reflexes between the arm and the trapezii were also recorded. Regardless of symptom localization, symptomatic keyboardists showed reduced activation of their lower trapezius muscle and abnormal reciprocal relationships between the upper and lower trapezii. Symptomatic subjects could however voluntarily activate their trapezeii and the trapezius reflexes were intact, suggesting the scapular instability was functional rather than physiologic. Symptomatic subjects also produced excessive activation of the elbow and finger extensors compared with asymptomatic keyboardists, perhaps to compensate for the scapular instability. The results suggest that scapular instability may be an important predisposing factor in overuse injury. Future studies should investigate if exercises that lead to activation and strengthening of the scapular stabilizers, particularly the lower trapezius, may be an effective preventive and/or treatment approach to PRMD.