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 (Vo(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: Vo(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 Vo(2) during walking and running were not altered by BWS. While walking, the RPE at a Vo(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 Vo(2) of 25 mL · kg(-1) · min(-1). Peak normal GRFs at specified Vo(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 Vo(2) during exercise and has minimal effect on the relationship of RPE with Vo(2), training heart rate and RPE values do not appear to require adjustment with partial BWS. Reduced GRFs at specified Vo(2) levels from partial BWS suggest that there are important clinical applications of this technology.