Dissociation in changes in EMG activation during maximal isometric and submaximal low force dynamic contractions after exercise-induced muscle damage

Abstract

Exercise induced muscle damage (EIMD) is characterized by muscle pain, symptoms of swelling, muscle shortening, increased serum creatine kinase activity, decreased force output and altered neuromuscular function. The aim of this study was to determine how the symptoms of EIMD influence the neuromuscular recruitment patterns during maximal and submaximal isometric and submaximal flexion–extension movements. Twenty-five right-handed males were recruited for this study, and were allocated to a control (n=13) or experimental group (n=12). In contrast to the control group, the experimental group participated in an EIMD protocol. Subsequently, symptoms of both groups were closely monitored for 132h. After the EIMD protocol, muscle pain scores in the experimental group peaked after 36h with creatine kinase activity peaking after 108h. Twelve hours after the EIMD protocol, EMG activity had decreased by 20% during a maximal voluntary contraction in the experimental group and decreased by a further 10% until the end of the study was reached 132h after the EIMD protocol. In contrast EMG during a submaximal flexion–extension movement increased significantly until the end of the study (132h). This dissociated EMG activity at submaximal and maximal intensity, suggests that central regulation influences the neural firing patterns and motor unit activity.