An electromyographic study of elbow motion during postexercise muscle soreness

Postexercise muscle soreness was induced in the elbow flexors of human volunteer subjects through the use of a regimen of eccentric contractions. Physical examination before and 48 h after the exercise included measurements of range of elbow motion at the elbow and of arm diameter. Electromyographic (EMG) observations, utilizing fine wire electrodes introduced into each of the elbow flexors, were carried out before and 48 h after the exercise. These observations included resting EMG levels, EMG activity under various isometric loads, and activity during active and passive extensions. The soreness induced was accompanied by a reduction in resting elbow angle while the subjects stood with arms relaxed at their sides, decreased range of both flexion and extension of the elbow, and swelling of the arm. EMG measurements showed no increase in EMG activity as the sore arms were extended passively at the elbow, indicating that the extra resistance to extension associated with the soreness was not a result of stretch receptor-induced activity in the flexors. The results rule out the possibility that neuromuscular activity is responsible for the restriction of motion and are consistent with the idea that edematous changes within the perimuscular connective tissue alter the elastic behavior of the muscles and cause restriction of motion.