We examined the ability of patients with spinal cord injury to undergo adaptations to chronic exercise training (cycle ergometry) invoked by functional electrical stimulation (FES) of the legs. Nine such patients performed incremental and constant work rate exercise before and after exercise training. Exercise sessions averaged 2.1 ± 0.4/wk, and consisted of 30 min/session of continuous FES recumbent cycling with increasing work rate as tolerated. Peak ˙VO2 and peak work rate significantly improved with training. Peak ˙VO2 was significantly correlated with peak heart rate both before and after training (r = 0.97 pre and 0.85 post, P < 0.01 for both). The time course of the˙VO2, ˙VCO2 and ˙VE responses to constant-load exercise (unloaded cycling) and in recovery (mean response time MRT) were very long prior to training, and became significantly faster following training. However, there was no correlation between percentage improvement in either MRTon or MRToff for ˙VO2 and the percentage increase in peak ˙VO2. Exercise tolerance in these patients with spinal cord injury appears to be a direct function of the ability to increase heart rate. Further, exercise training can elicit significant improvements in both exercise tolerance and in gas exchange kinetics, even when performed only twice per week. However, these improvements may be accomplished by different mechanisms.
Division of Respiratory and Critical Care Physiology and Medicine, Department of Medicine, Harbor-UCLA Medical Center, Torrance, CA 90509; Physical Medicine and Rehabilitation Service, West Los Angeles Veterans Affairs Medical Center, Los Angeles, CA 90073; Department of Medicine, University of California, Los Angeles, CA 90024; Physical Medicine and Rehabilitation Service, Albuquerque Veterans Affairs Medical Center, Albuquerque, NM 87108; Department of Orthopedics, University of New Mexico, Albuquerque, NM 87131; St. George's Hospital Medical School, Department of Physiology, London, UNITED KINGDOM
Submitted for publication March 1995.
Accepted for publication December 1995.
Address for correspondence: Thomas J. Barstow, Ph.D., Department of Kinesiology, 8 Natatorium, Kansas State University, Manhattan, KS 66506-0302.