Virtual reality systems have been used to deliver goal directed repetitive training to promote rehabilitation of individuals post-stroke. Lower extremity training of individuals post-stroke who used a robot coupled with virtual environments was shown to transfer to improved over-ground locomotion. To elucidate an underlying mechanism that enabled this functional change we compared the kinetic outcomes of training with the robot-virtual reality (VR) system to the robot alone. Eighteen individuals post-stroke participated in a four-week training protocol. One group trained with the robot-VR system and the other group with the robot alone. Training parameters were comparable for the two groups; however, the improvements in moments and powers generated in the ankle and hip of subjects in the robot-VR group were significantly greater than those in the robot alone group. These findings demonstrate that lower extremity training using virtual environments coupled with a robot produced greater gait related strength gains than training with robot alone.