Anticipatory EMG patterns associated with preferred and non-preferred arm pointing movements.

Rapid arm movements generate balance perturbations, which are anticipated and counteracted by postural adjustments. The effect of lateral preference on the control of the postural preparation to maximal velocity upperlimb pointing movements was investigated in right-handers. The muscular activities characterizing the postural adjustments were compared for preferred and non-preferred upper-limb movements. Movements were performed in two sitting conditions differing by their stability ("full on seat" and "edge of seat"). The electromyographic activity of the arm-movement prime mover and of several trunk and hip muscles involved in postural control was recorded with surface electrodes. Results indicate the presence of a reproducible pattern of anticipatory postural adjustments (APAs) involving trunk and hip muscles preceding the activation of the prime mover. In the "full on seat" condition, APAs started earlier and movement velocity was higher for preferred than for non-preferred arm movements. In the "edge of seat" condition, maximal velocity of movement did not differ significantly between both sides, but a higher excitation level of postural muscles was required to achieve this similar performance when the non-preferred upper limb was used. These findings are consistent with the hypothesis that handedness involves differences in the postural control associated with upperlimb movements, in other words that lateral preference is associated with a postural laterality.