Energetic and Hemodynamic Response to Electrical Stimulation Cycling in Persons with Paralysis

Abstract

Electronic stimulation can be used to stimulate contraction of paralyzed muscle, and when coordinated via computer processing, lower body muscles can power a cycle ergometer in a manner which increases whole-body energy expenditure. PURPOSE: When matched for charge input determine if calorie (kcal) expenditure and fuel partitioning measured during and immediately following a bout of functional electrical stimulation (FES) cycling differed when performed on two FES devices. METHOD: Six males with spinal cord injury (SCI; age: 49±17 yr; weight: 76±6 kg; level of injury: C4-T11) completed 30 min of steady-state FES exercise on four separate occasions at a charge-matched moderate stimulation intensity. Two sessions were completed on a commercially available unit (RT300, Restorative Therapies, MD) and two on a device that is in pre-production testing (MyoCycle, MYOLYN, FL) that employs a different electrical control paradigm. Before, during, and after cycling, energy expenditure and fuel homeostasis were calculated via pulmonary gas exchange (Oxycon, Jeager, CA), and central hemodynamics (for the MyoCycle device only) via impedance cardiography (PhysioFlow, Manatec Biomedical, FR). RESULTS: Rate of oxygen consumption (VO2) and cardiac output (CO) during FES were 34±20% and 49±23% of their respective VO2peak and COpeak achieved during maximal effort arm cycling. Both FES devices elicited similar rates of exercise energy expenditure (1.06±0.20 kcal/min) and fuel homeostasis (74:26 %CHO:%FAT). However, only the MyoCycle showed a statistically significant increase in energy expenditure at 20-30 min post-exercise time point (11.2% increase vs pre-exercise, p=.02), with this increase in energy expenditure accompanied by a 54% increase in CHO oxidation during the first 30 min of exercise recovery. CONCLUSION: Moderate intensity FES cycling qualifies as “low intensity” aerobic exercise according to authoritative guidelines, although increases in carbohydrate oxidation during and after cycling might have a meaningful impact on daily glucose regulation. Furthermore, the energetics of the recovery period seem to be influenced by the electrical control system.