An electromyographic study of upper limb adduction force with varying shoulder and elbow postures

The purpose of this study was to study the electromyographic (EMG) activity of shoulder and arm muscles during force generation in different shoulder and elbow positions when performing an isometric adduction. EMG from four pairs of muscles (biceps, anterior deltoid, pectoralis and flexor carpi radialis) were recorded bilaterally in 10 healthy young males who performed a two-handed maximal adduction against the lateral sides of the force measuring device. Descriptive statistical analysis and analysis of variance were carried out for average and maximal force. Multivariate analyses were performed to explore the relationship between force and EMG at intervals of 20% of the maximal voluntary force (contraction). The results showed that the EMG activity was significantly affected by posture (P < 0.001) but not by symmetry. The Pearson correlation coefficients were low, especially for the flexor carpi radialis and deltoid. The results revealed that the EMG activity increased with the increase in forward flexion of the shoulder, whereas the forces decreased.