Physiological comparison of walking among bilateral above-knee amputee and able-bodied subjects, and a model to account for the differences in metabolic cost

Abstract

Objectives: To compare the metabolic cost for prosthetic ambulation among persons with bilateral above-knee amputation with that for able-bodied ambulation, and to test a model that differentiates the metabolic cost of walking into three components. Design: Cross-sectional comparison. Setting: Community-dwelling subjects studied at an academic medical center. Participants: Five bilateral above-knee amputee subjects with mean (±SD) age of 22 ± 3 years, and five able-bodied control subjects matched for gender, height, weight, and age. Intervention: Subjects performed 6-minute bouts of walking at three paced speeds and their chosen walking speed with oxygen uptake being determined during the last 2 minutes of each bout. Main Outcome Measures: Chosen walking speed and oxygen uptake during each walking condition. Results: The chosen walking speed was 21% slower and induced aerobic demands 49% higher for the amputee subjects. Across specified paced speeds, aerobic demands were 55% to 83% higher for the amputee subjects than for the able-bodied subjects. The described model suggests that the higher metabolic costs for the amputee subjects resulted from greater demands for maintenance of balance and posture and for performing the walking movement. Conclusions: Prosthetic ambulation by young healthy persons with bilateral above-knee amputation induces significantly greater metabolic demands than walking by able-bodied individuals. Although the chosen walking speed of persons with bilateral above-knee amputation is slower, the reduction in speed is insufficient to equalize their metabolic cost with that of able-bodied individuals walking at their chosen walking speed.