Three dimensional preparatory trunk motion precedes asymmetrical upper limb movement

Three-dimensional trunk motion. trunk muscle electromyography and intra-abd ominal pressure were evaluated to investigate the preparatory control of th e trunk associated with voluntary unilateral upper limb movement. The direc tions of angular motion produced by moments reactive to limb movement in ea ch direction were predicted using a three-dimensional model of the body. Pr eparatory motion of the trunk occurred in three dimensions in the direction s opposite to the reactive moments. Electromyographic recordings from the s uperficial trunk muscles were consistent with preparatory trunk motion. How ever, activation of transversus abdominis was inconsistent with control of direction-specific moments acting on the trunk. The results provide evidenc e that anticipatory postural adjustments result in movements and not simple rigidification of the trunk. (C) 2000 Elsevier Science B.V. All rights res erved.