Adaptational effects during human split-belt walking: influence of afferent input.

The modification of the normal locomotor pattern of humans was investigated using a split-belt locomotion protocol (treadmill belt speeds of 4.5 km/h and 1.5 km/h for the right and left legs, respectively) and also by changing afferent input from the legs (30% reduction or increase in body weight by suspending subjects in a parachute harness or by wearing a lead-filled vest). After a control-speed training period (10 min) of symmetrical walking (3 km/h each leg) and a period (10 min) of split-belt walking, the adjustment back to the control speed resulted in a mean speed difference between the right leg and the left leg of 0.85 km/h. Adjustment of belt speed on either side was performed by the hands using a potentiometer. For comparison, also speed adjustment by the feet via feedback derived from changes in the treadmill drive current was studied. No significant difference was obtained when both modes of adjustment were compared. Body unloading or loading during the training period resulted in an improved adjustment of treadmill belt speed. This suggests that load receptor information plays a major role in the programming of a new walking pattern.