Effect of grip span on maximal grip force and fatigue of flexor digitorum superficialis.

The aim of this study was to investigate the effect of grip span on isometric grip force and fatigue of the flexor digitorum superficialis (FDS) muscle during sustained voluntary contractions at 60-65% of the maximal voluntary contraction (MVC). Eighteen subjects performed isometric, submaximal gripping contractions using a grip dynamometer at four different grip span settings while the pronated forearm rested on a horizontal surface. Maximal absolute grip force and median power frequency of FDS surface electromyography (EMG) during the submaximal trials were analyzed. Fatigue of FDS, as inferred from EMG frequency shifts, did not change as a function of grip size. However, middle grip sizes allowed for greater absolute forces than the small or large size. When contractions are at 60-65% MVC and the muscle is allowed to fatigue, however, grip size may be less influential than when maximal absolute force is required.