THE COMBINED CONTROL OF LOCOMOTION AND PREHENSION

This study investigated the strategies used by individuals when the lo comotor and prehensiIe motor systems are used simultaneously. Subjects were required to perform five tasks: to walk normally, walk and pick up a small object, walk and pick up a large object, and finally pick u p small and large objects from a standing position. The general organi zation and control of lower limb movements was largely unaffected by t he introduction of reaching movements. However, arm movements were gen erated faster when subjects were walking (both when walking and reachi ng together, and walking alone), suggesting that the discrete reach is superimposed upon the normal swing of the arms during walking. Record ings of muscle activity of the upper limb confirmed this observation. The stability of gait while grasping indicates that the motor control system may be organized such that the stability of gait is maintained over variations in the control of grasping.