Development of an isokinetic FES leg stepping trainer (iFES-LST) for individuals with neurological disability

Abstract

An exercise device, employing functional electrical stimulation (FES) of leg muscles and a seated elliptical stepping mechanism, was developed for people with neurological disabilities. A feedback motor control system was developed to maintain constant (“isokinetic”) pedalling cadence, and the device could both assist legs with poor muscle power as well as resist a stronger stepping effort. FES was employed to recruit particular leg muscle groups in a pattern that resembled voluntary elliptical stepping. To switch the electrical stimulation on and off, the pedal crank's angular position was used to identify the foot's instantaneous position throughout the movement path. Thus, key lower limb muscles (quadriceps, hamstrings, gluteals) could be exercised in this population with muscle weakness or paralysis. Stepping cadence, stimulation current level and each muscle group's stimulation angle could be modified ad-hoc, while the power output responses were monitored to fine tune the quality of leg exercise.