Physiological Responses to Body Weight–Supported Treadmill Exercise in Healthy Adults

Abstract

Hoffman MD, Donaghe HE. Physiological responses to body weight–supported treadmill exercise in healthy adults. Objective To determine whether the relationships of heart rate, rating of perceived exertion (RPE), and ground reaction forces (GRFs) with oxygen consumption rate (V̇ o 2) during treadmill exercise are altered by partial body weight support (BWS) via lower-body positive pressure. Design Repeated-measures design. Setting Exercise physiology laboratory. Participants Healthy, active adults (N=12); mean age ± SD, 45.1±12.6 years. Interventions Not applicable. Main Outcome Measures V̇ o 2, heart rate, RPE, and GRFs were measured during walking and running at 3 levels (0%, 25%, 50%) of BWS. Before exercise, standing heart rate and blood pressure were measured under each BWS condition. Results Standing heart rates were 7 beats/min lower ( P<.05) and systolic blood pressures were 10mmHg higher ( P<.001) at 50% BWS compared with 0% BWS, but mean blood pressure while standing and the relationship of heart rate with V̇ o 2 during walking and running were not altered by BWS. While walking, the RPE at a V̇ o 2 of 10 mL · kg –1 · min –1 was statistically lower ( P<.05) at 0% BWS compared with 25% and 50% BWS (mean values, 7 vs 8 points), but RPE was not different among conditions while running at a V̇ o 2 of 25 mL · kg –1 · min –1. Peak normal GRFs at specified V̇ o 2 levels and RPE values were reduced ( P<.05) with increasing BWS for walking and running. Conclusions Because partial BWS does not alter the relationship of heart rate with V̇ o 2 during exercise and has minimal effect on the relationship of RPE with V̇ o 2, training heart rate and RPE values do not appear to require adjustment with partial BWS. Reduced GRFs at specified V̇ o 2 levels from partial BWS suggest that there are important clinical applications of this technology.