Temporal characteristics of cervical muscle activation patterns before, during and after the completion of a repetitive arm task

Abstract

Cervical pain has previously been linked with abnormal activation patterns at rest and during movement; however, few studies have assessed how recovery patterns immediately following an arm task may be associated with symptoms. As a first step, the objective of this study was to quantitatively describe the activation and recovery patterns of the cervical musculature before, during and after a repetitive arm task in asymptomatic people. We recorded bilateral surface electromyography (sEMG) from the Sternocleidomastoid (SCM), Scalenus Anterior (SA), Upper Trapezius (UT) and Cervical Erector Spinae (CES) muscles at rest before, at three time points during a 2.5min repetitive unilateral arm task, immediately after and every minute for five minutes at rest after the task. ANOVA analyses with within-subject factors of Time and Muscle were performed on each subject's average and standard deviation values of each muscle's EMG rootmean squared (RMS) amplitude calculate across 1s samples. Results show that there was a significant interaction effect (p<0.0001), showing that muscles responded differently through time. There were main effects of Time on the mean peak amplitude for all muscles, with the majority of the activity peaking during the middle of the task. There were main Time effects on amplitude variability for SCA and UT muscles that also showed increases during the task but that occurred at the same time or earlier than when peak activity was reached. Findings suggest that pre-task sEMG amplitude levels were reached immediately upon completion of the task in asymptomatic subjects and that this could have been accomplished by modulating amplitude variability early on in the task. © 2011 Springer-Verlag.