(A) Raw sled velocity trace showing one of the predetermined sled velocity peaks used for stepping measurements (circle). (B) Magnified traces showing the initial visual screening carried out to identify the occurrence of a foot response (horizontal oval). The solid vertical line shows the peak forward sled velocity, and the dotted line shows the onset of the forward velocity stimulus (i.e. the point at which sled velocity reverses direction and, in this case, begins to move forwards). (C) Same trace as in B. The time between the dotted line (stimulus onset) and solid vertical line (foot lift onset) measures the foot latency (in ms). The sled velocity at the onset of foot lifting denotes the stepping threshold (in m/s).