Arm muscle activity with no positive effect on ball speed during full effort pitching

Abstract

The purpose of this study was to examine muscle activity that does not positively affect pitch velocity by comparing throwing arm muscle activity during full strength and force-regulated pitching. Subjects threw a baseball at 80% and 100% subjective intensity. Muscle activity of the biceps brachii (BB), triceps brachii (TB), flexor carpi ulnaris (FCU) and extensor carpi radialis (ECR) muscles was measured using a wireless EMG measurement system (Trigno wireless EMG system: Delsys Inc.) and compared between conditions. The co-contraction index (CCI) was also calculated during the comparison. Despite significant differences in velocity between the two conditions, there was no difference in throwing arm muscle activity or forearm co-contraction index from 190 ms before release to release. Upper arm co-contraction index was higher when throwing at full speed. Furthermore, we also analyzed whole-body muscle activity and found differences in lower extremity/trunk and nonthrowing arm muscle activity. The results of this study provide new insights into the motor control mechanisms that regulate pitch velocity in skilled pitchers.