Anticipatory postural adjustments in a bimanual, whole-body lifting task seem not only aimed at minimising anterior-posterior centre of mass displacements

Anticipatory postural adjustments (APAs) were studied in a bimanual whole-body lifting task, using a mechanical analysis of the downward movement phase preceding loaded versus unloaded lifts. APAs in the backward ground reaction force were found to lead the perturbing forward box reaction with - 400 ms, thus inducing a backward cent re of mass momentum. Both the APA onset and magnitude were scaled as a function of the load to be lifted. We conclude that, in this lifting task, the APAs served the generation of an appropriate extending moment of the ground reaction force after box pick-up, rather than the traditionally defined goal of minimising anterior-posterior centre of mass displacements. (C) 2001 Elsevier Science B.V. All rights reserved.