Transient Postural Sway Occurring after Treadmill Walking: Effects of Different Image Presentation

Treadmill exercise has the specific aftereffect that, in stepping down onto the floor after exercise, a person has the perception of self-motion and sways forward. It has been speculated that treadmill exercise is accompanied by an adaptation process in the postural control system because of a mismatch between the visual and somatosensory input, and thus the aftereffect occurs as re-adaptation to normal postural control. However, nobody has yet succeeded in showing whether the extent of the mismatch between the visual and somatosensory input during treadmill exercise influences the aftereffect. In the present study, we used a video image of sufficient reality to induce self-motion perception, and changed the visual input during treadmill exercise to vary the mismatch level. As a result, the aftereffect was significantly reduced by normally-directed visual stimuli and significantly increased by reverse-directed visual stimuli. In conclusion, a correlation was found between the level of the mismatch and the aftereffect, supporting the view that aftereffects are caused by a mismatch of the visual and somatosensory input during treadmill exercise.