AN ENHANCED FES LEG CYCLE ERGOMETER FOR THE SCI 640

Abstract

The original Therapeutic Alliances, Inc. model ERGYS functional electrical stimulation (FES) leg cycle ergometer (LCE) induces therapeutic exercise of the paralyzed quadriceps, hamstring and gluteal muscle groups of persons with spinal cord injury (SCI) to promote muscular and cardiopulmonary fitness. We modified this instrument in an effort to enhance physiologic response magnitudes. The purpose of this study was to compare peak metabolic and cardiopulmonary responses during stress testing with the original and an enhanced ERGYS FES-LCE. Modifications consisted of increasing max FES current output from 140 to 300 mA, adding the tibialis anterior and gastroc-soleus muscle groups, increasing the FES firing angle ranges by 55°, and utilizing an external flywheel resistance controller for immediate and continuous setting of load without stopping exercise to reprogram the system. Eight subjects with lower-limb paralysis due to SCI volunteered to participate. A continuous stress test protocol was used where the target pedal rate was 50 rpm. Exercise commenced at 0 load for 2 min, and power output (PO) was increased by 3.1 W (i.e., 1/16 kp) increments at 2-min intervals until fatigue caused rpm to drop to 35. At max PO, peak oxygen uptake (VO2), pulmonary ventilation (VE), heart rate (HR), stroke volume (SV), cardiac output (Q) and blood lactate concentration (LA) were determined. We found that max PO for the enhanced vs original ERGYS was similar. Lack of greater PO for the enhanced ERGYS was probably due to the fatiguing effects of the longer contraction duty cycle with wider firing angle ranges. However, the enhanced ERGYS elicited higher (p<.05) peak VO2(+16.1%), VE(+43.4%), HR (+25.3%), SV (+10.2%), Q (+36.2%) and LA (+52.3%). Greater peak metabolic and cardiopulmonary responses obtained via the incorporated modifications to the FES-LCE may permit greater muscular and cardiopulmonary training capability.