THE EFFECTS OF ASSISTIVE DEVICES ON THE OXYGEN COST, CARDIOVASCULAR STRESS, AND PERCEPTION OF NONWEIGHT-BEARING AMBULATION

Nonweight-bearing ambulation with the aid of an assistive device is often prescribed in the clinical setting. Little is known about the oxygen cost, cardiovascular stress, and perception of effort of these devices when applied to the same sample of subjects. Therefore, the present study compared the oxygen cost, cardiovascular stress [measured by heart rate (HR), blood pressure (BP) responses, and rate pressure product (RPP)], and perception of effort [measured by ratings of perceived exertion (RPE)] of unassisted ambulation (UA), nonweight-bearing ambulation using axillary crutches (AC), a standard walker (SW), and a wheeled walker (WW). Nine female subjects ambulated at self-selected velocities for 7 minutes during each ambulation mode. Oxygen consumption, HR, BP, and RPEs were obtained. As expected, UA resulted in the lowest VO2 (11.2 +/- 1.4 ml/kg . min-1) and greatest velocity (1.24 +/- 0.27 m/sec). Results also indicated that AC ambulation resulted in lower oxygen consumption per meter (0.4 +/- 0.1 ml/kg . m-1) and greater velocity (0.74 +/- 0.18 m/sec) than either SW ambulation (0.6 +/- .1 ml/kg.-1, 0.39 +/- 0.09 m/sec) or WW ambulation (0.6 +/- .1 ml/kg.m-1, 0.40 +/- 0.12 m/sec) (p <.05). No differences were observed among assisted ambulation modes for HR, BP responses, RPP, or RPE values. Because patients typically ambulate for a set distance (rather than a set time) and because the oxygen cost per unit distance was lowest for AC, it is suggested that, when possible, AC should be prescribed for nonweight-bearing ambulation.