Quiet stance control is affected by prior treadmill but not overground locomotion

Treadmill locomotion is different with respect to overground walking and may require an adapted control mode. The relevant neural computational effort may produce lasting effects encroaching upon the performance of a subsequent postural task. The hypothesis of the present study was that, contrary to overground walking, treadmill walking has effects on quiet stance variables, in the assumption that the imposed locomotor activity is more critical to stance control than natural walking. Nine young subjects performed three different walking sessions: treadmill with eyes closed, treadmill with eyes open, overground walking with eyes open. Body sway area and sway path and the position of the centre of foot pressure during stance were recorded by a dynamometric platform under control, post-walking and post-recovery conditions, alternatively with eyes closed and eyes open. At variance with overground walking, treadmill locomotion produced an effect on body orientation in space during the subsequent stance trials. This consisted in a forward inclination of the body, not accompanied by increased body sway, lasting for a few minutes. Presence or absence of vision during treadmill locomotion did not induce differences in the amplitude or time-course of the post-effect. We argue that body inclination would be the consequence of a change in the postural reference produced by a message arising from treadmill locomotion itself, possibly connected to particularities in the control mode of this type of walking.