Fig. 2

Data analysis. (A) Toe velocity profile from a single trial. We used the peaks (red and blue dots) and valley (black dot) of the toe velocity signal to characterize the reversal phase of the movement. This phase consisted of an initial deceleration towards the target (thick red line) followed by acceleration away from the target back toward the start position (thick blue line). (B) Toe trajectory profile of data shown in A. We used toe trajectory to calculate measures of end-point accuracy. We used toe position at the reversal point (black dot) as the end-point position for each trial. We then calculated the horizontal (h) and vertical (v) end-point errors as the vertical and horizontal distance of the end-point relative to the target. We calculated foot-path area by determining the area encompassed by the toe during the reversal phase (checkered area). The red and blue dots indicate the first and second peaks in toe velocity, respectively, and define the reversal phase (see A). (C) We used a three-segment (thigh, shank, foot) lower limb model that was interconnected via frictionless joints (hip, knee, ankle). We calculated segment angles relative to the right horizontal. Segment angles and their derivatives (velocity and acceleration), alongside anthropometric measurements, were used in the equations of motion to calculate joint torques [32]. We quantified joint torques over the first half of the reversal phase (thick red line in A)