Development of an Isokinetic Functional Electrical Stimulation Cycle Ergometer

An isokinetic functional electrical stimulation leg cycle ergometer (iFES-LCE) was developed for individuals with spinal cord injury (SCI). The iFES-LCE was designed to allow cycle training over a broad range of pedalling cadences (5-60 rev/min) to promote both muscular strength and cardiorespiratory fitness. A commercially available motorized cycle ergometer was integrated with a custom built FES system, a laptop computer, and a specialized chair that restricted lateral leg movements. Sample biomechanical data were collected from an SCI subject performing FES cycling to demonstrate the IFES-LCE's performance characteristics. Calibration of the IFES-LCE system revealed a linear relationship between torque applied to the axle of the motorized ergometer and the braking motor current generated to maintain velocity. Performance data derived from iFES-LCE motor torque agreed closely with similar data collected using strain-gauge instrumented pedals (cross-correlations = 0.93-0.98). The iFES-LCE was shown to work well across a range of pedaling cadences. We conclude that the new iFES-LCE system may offer improved training potential by allowing cycling over a broad range of pedaling cadences, especially low cadence. This device also improves upon the accuracy of other ergometers by adjusting for the passive load of the legs.