Target height affects the symmetry of the postural adjustments after (but not prior) the onset of reaching movements in upright standing

The present study aimed to investigate the influence of target height on the symmetry and amplitude of the postural adjustments assessed by the displacements of the center of pressure (COP) before and during the unilateral, arm movements in the upright position. Thirteen young, right-handed adults stood with each foot on one force platform and reached a target placed at one of three heights displayed on a monitor screen. The performance of the right arm movements (movement time and radial error), amplitude of the COP displacements of each lower limb and the percentage of body weight loading on the right lower limb before and during the reaching movements were compared across target heights conditions. Postural adjustments were symmetrical prior but asymmetrical after movement onset. Effect of target height was observed on the postural adjustments before and during the movements (i.e., amplitudes of the COP displacements increased for the higher target), mainly for the right limb. The arm performance was similar across target heights. The findings of the present study suggested that postural adjustments are dependent on the target heights to ensure success in the arm movements.