Grip strength gain after submaximal isometric wrist extension training without gripping motion

Abstract

  Gripping force depends on wrist position and was requires co-contraction of forearm flexors and extensors. Especially, the activation of forearm extensors is important for stabilization of the wrist. Therefore, the purpose of this study was to investigate whether wrist extension training without gripping motion would change gripping force-wrist angle curve and forearm muscle activation during gripping. 12 healthy subjects participated in this study. Grip strength with maximal effort and EMG of six forearm muscles (FCR, FCU, FDS, ECR, ECU and EDC) from 70 degrees flexion to 80 degrees extension at wrist were measured simultaneously at baseline and 4 weeks after training. The training was isometric wrist extension without gripping motion, which consisted of 30 repetitions equal to 70%MVC for 4 weeks (5/wk). Wrist angle at maximal gripping force was calculated from the relationship between the wrist angle and grip strength. The data investigated the training effects on grip strength and EMG activation, and the gain in wrist flexion or extension. Wrist extension force and grip strength increased significantly. But, wrist angle at maximal grip strength did not change. EMG activation of flexors did not change, but that of extensors increased significantly after training. And gain of grip strength and EMG activation of extensors in flexion range was larger than that in extension range. Wrist extension training without gripping force leads to an increase in grip strength; therefore this training program used in this study would be an effective training strategy for increasing grip strength.