DELAYED ONSET MUSCLE SORENESS ALTERS MYOELECTRIC ACTIVITY

Abstract

201 This study sought to investigate changes in myoelectric activity during delayed onset muscle soreness (DOMS) in thirty-six college-aged males. Maximal isometric force (MVC) scores, myoelectric activity during submaximal (20%) isometric contractions, and visual analog scale soreness scores (VAS, 100 units) were obtained immediately prior to and 36 hours after an exercise protocol. Subjects performed two sets of 25 maximal eccentric contractions with a five-minute rest between sets. All test contractions were performed on a biceps curl bench with the elbow angle fixed at 90 degrees and the wrist rigidly coupled to a force transducer providing force feedback in real time. Subjects performed three 7-second contractions at 20% MVC and surface EMG was sampled at 1 kHz with electrodes placed over the biceps brachii. The exercise protocol produced a significant 53% force loss from baseline to 36-hours post exercise and perceived soreness increased significantly from 2.3 to 63.6 VAS units. Myoelectric amplitude significantly increased by 130%. Median EMG frequency showed a non-significant decrease of 4.8%. These results show that post-exercise DOMS is accompanied by dramatic increases in the myoelectric signal amplitude. Motor unit recruitment and/or firing rate increases may compensate for an impaired contractile mechanism. Motor unit recordings would provide more conclusive information regarding the motor unit behavior, which underlies measures of myoelectric activity.