CONTROL STRATEGIES OF THE ELBOW ANTAGONIST MUSCLE PAIR DURING 2 TYPESOF INCREASING ISOMETRIC CONTRACTIONS

The purpose of this study was to determine if differences exist betwee n the control strategies of the elbow flexor and extensor muscles perf orming stepwise and linearly increasing isometric contractions, and to determine their control strategy when active as antagonists to each o ther. The electromyogram (EMG) from the biceps brachii and triceps bra chii were recorded during stepwise and linearly increasing contraction s in flexion and extension. The power density spectrum of the EMG was determined and the median frequency (MF) for each spectrum was calcula ted for assessment of changes in the average conduction velocity, whic h reflects motor unit recruitment and derecruitment, and thereby the c ontrol strategy of the muscle. The results suggest that differences ex ist in the control strategies employed by a single muscle during stepw ise and linearly increasing contractions. Furthermore, the antagonist triceps recruits motor units up to a higher force level during stepwis e contractions than during linearly increasing contractions. The antag onist biceps derecruits motor units up to a higher force level during linearly increasing contractions than during stepwise contractions.