This article presents the development of a support tool for human gait therapy and diagnosis. This system is made of an electric treadmill with horizontally parallel graduable support bars and a positioning control system of a patient during forward gait. The control objective consists in keeping the patient around the center of the treadmill, with a spontanous gait speed of the subject as the main disturbance. Actuation on the speed reference of the treadmill is made using a modification on the manual speed controls included in the commercial treadmill used. A Kinect sensor is used for measuring the position of the patient on the treadmill. Successful results of implementation and basic operation of the whole system are reported.