LAUSR

OBJECTIVES 1) Compare energy expenditure during seated rest, standing, and prolonged bionic ambulation (BA) or bipedal ambulation in participants with SCI and non-injured controls (CON), respectively, and 2) test effects on post-BA glycemia in SCI. DESIGN Two independent group comparison of SCI and CON. SETTING Academic Medical Center. PARTICIPANTS 10 chronic SCI (C7-T1, AIS A-C) and 10 CON. INTERVENTIONS A commercial bionic exoskeleton. MAIN OUTCOME MEASURES Absolute and relative (to peak) oxygen consumption, perceived exertion, carbohydrate/fat oxidation, energy expenditure, post-BA plasma glucose/insulin. RESULTS Average work intensity accompanying 45 minutes of outdoor BA was <40% VO2peak, with negligible drift after reaching steady-state. RPE did not differ between groups and reflected low exertion. Absolute energy costs for BA and non-BA were not different between groups, despite a 565% higher ambulation velocity in CON and 3.3x higher kilocalorie/meter in SCI. Fuel partitioning was similar between groups and the same within groups for carbohydrate and fat oxidation. Non-significant (9%) lowering of the area under a glucose tolerance curve following BA required 20% less insulin than at rest. CONCLUSION Work intensity during prolonged BA for this bionic is below a threshold for cardiorespiratory conditioning but above seated rest and passive standing. BA metabolism is consistent with low RPE and unchanged fuel partitioning from seated rest. BA did not promote beneficial effects on glycemia in well-conditioned, euglycemic participants. These findings may differ in less fit individuals with SCI, or those with impaired glucose tolerance. Observed trends favoring this benefit suggest they are worthy of testing.