 This study investigated how human gait responds to periodic torque pulses applied to the ankle joint. It was found that the gait entrains to the pulses when the pulse period is close to the preferred stride duration. Furthermore, the gait exhibits a constant phase relationship with the pulses, such that the robot provides maximum mechanical assistance. This suggests that the robot can be used to provide mechanical assistance to improve gait in patients with impairments. This article was authored by Zhang Wuli, Megan E. Huber and Neville Hogan.