Fig. 1.

Methods. A: experimental protocol. Children walked on a split-belt treadmill with the belts at the same speed (tied), followed by the belts at different speeds (split), and finally again in the tied condition. Time periods of interest are late baseline (open bar), early split (shaded bar), late split (hatched bar), and early postsplit (stippled bar) at 40 steps for each period. B: temporal measures of walking are shown: stride time, stance time, and double support time. Open and shaded horizontal bars indicate the duration of the stance phase, and the space between the bars represents the duration of the swing phase. The duration of a stride includes a stance and a swing phase. Temporal coordination was quantified by double support times (i.e., time when both feet are in contact with the ground), shown for when the slow leg is trailing (slow DS) and when the fast leg is trailing (fast DS). C: center of oscillation is the mean limb angle over a stride. Limb angles of the fast (solid line) and slow (shaded line) legs are plotted for 1 child (35.2 mo) during early split. Dashed horizontal solid and shaded lines represent the mean limb angles for the fast and slow legs, respectively. Limb angle is the angle between the vertical and a vector connecting the hip and ankle markers (shaded line in inset at right). D: step length and stride length are illustrated. Step length, defined as the distance between the ankle markers of the 2 legs in the anteroposterior direction, was measured at the time of foot contact of the leading limb (i.e., instant in time illustrated at middle and right). The step lengths are named according to the leading leg, by convention. Stride length (left) is the distance traveled in the anteroposterior direction by the ankle marker of a single leg through the stance phase (i.e., foot contact to lift off, limb position shown for the 2 instances in time).