Behavior of dominant and non dominant hands during ballistic protractive target-directed movements.

The purpose of this study is to investigate the asymmetry of dominant and non-dominant arms regarding reaction time (RT), velocity, force and power generated during ballistic target-directed movements. Fifty six, right-handed young males performed protractile movements with both arms separately by pushing a joystick towards a target-line as quickly and as accurately as possible. Participants performed 21 repetitions with each hand. The temporal, spatial, kinetic and kinematic parameters were computed. All movements were grouped regarding their accuracy (when joystick fell short, stopped precisely or overreached the target). Each group of movements was analyzed separately and the data obtained was compared across groups. The results showed that although the left arm was less accurate than the right one, it reached the target significantly faster, developing greater average force and power. The forces of acceleration and deceleration of the left arm were greater too. We did not observe a significant lateral difference in RT in situations when the arm fell short of the target, or stopped precisely on the target. It was only when the target was overreached that the left arm displayed a significantly greater RT than the right one. We explain the results from the asymmetry of motor behavior in favor of the influence of both hemispheres in this process.