Anticipatory neck muscle activity associated with rapid arm movements.

This study reveals the existence of a backward acceleration of the head prior to the onset of voluntary raising movements of the upper limb. This backward acceleration is produced by the displacement of the head-trunk as a whole. The anticipatory head movement is organized according to a sequence of activation and desactivation of the neck muscles, time locked with the anticipatory leg muscle activity. These findings highlight the existence of a complex postural behavior selected in advance of movement. It is proposed that the feedforward type of neural control of neck muscles should not be interpreted as a compensation to postural perturbation. This anticipatory process might play an important role in the widespread postural fixation of the cervical and dorsal spine.