Effect Of Handedness On Functional Organization Of Bimanual Isometric Handgrip

The aim of this study was to examine force production during maximal isometric handgrip in unilateral (UL) and bilateral (BL) tasks in right- and left-handed subjects. Ten right-handed (RH) and 8 left-handed (LH) young men were studied. The subjects were instructed, after a command, to perform a shot-like handgrip, raising maximal force as fast as possible. Three series were performed as follows: 1) UL - right handgrip; 2) UL - left handgrip; 3) BL handgrip. We measured peak force, time to peak of force and rate of force. The BL/UL ratios for the right (R) and left (L) hand and L/R ratios for the UL and BL tasks were calculated. The L/R ratios for peak force and force rate in RH group ranged across all tasks and conditions from 0.71 to 0.75. They were significantly lower than 1 (p<0.01). These ratios did not differ significantly from 1 for LH subjects (0.98–1.02), indicating the handedness in RH group only. The BL/UL ratios for peak force were 0.89 and 0.89 in RH, suggesting symmetrical bilateral strength deficit. The magnitude of the bilateral deficit in LH group was larger for the dominant (L) hand compared to non dominant (R) hand – 0.93 and 0.97 (p<0.05) respectively, suggesting an asymmetry of bilateral deficit in LH. These ratios for time of force and rate of force indicated bilateral deficit (BD) in the dominant hand of RH group only.