Head kinematic during various motor tasks in humans.

Head kinematic during various motor tasks was studied in ten subjects. The movement of the body was recorded with a video system (E.L.I.T.E.) which allows a computer reconstruction of three-dimensional motion of selected points on the body. Analysis is focused on head rotation in the horizontal and vertical planes. The results demonstrate that the amplitude and the maximum velocity do not exceed respectively 38 deg/s and 185 deg/s. However the head is intermittently stabilized and the angle of this stabilization is dependent upon the task and related to the direction of gaze. Darkness had no significant effect on head rotational velocity during walking but caused a decrease in velocity during running and hopping. The results suggest that head stabilization (1) is related to an ocular fixation point in the direction of gaze in space and (2) is probably regulated on the basis of a predictive mode of sensory motor control.