(A) Schematic representation of active robotic training. ( B) Construction of target-template trajectory – the target-template trajectory was constructed from the ensemble average of the baseline hip and knee trajectory with a scaling factor of 0.2. The scaling factor represents the amount of additional hip and knee flexion angle required from the baseline gait (i.e., when there is no tracking involved). In this case, the subject had to increase his hip and knee joint angle by 20% to match this target-template. The actual trajectory represents the ensemble average of the baseline trajectory computed from the hip and knee joint angle recorded during the baseline walking (C) Computation of target-tracking error – the error during target-tracking was calculated by determining the area that was not common to both the target-template and the actual trajectory during each gait cycle (shaded region). The resulting area (i.e., error) was normalized to the area of the target-template in order to compute % error during target-tracking.