The improvement of walking speed after cardiac rehabilitation is associated with the reduction in the metabolic cost of walking in older persons

摘要

Background: To walk a given distance older persons consume more metabolic energy than younger adults across all speeds. As physical activity interventions improve a variety of physical performance measures in older persons, including walking speed, in this study we hypothesized that the improvement of walking speed might be associated with the reduction of the metabolic cost of walking and we tested our hypothesis in a selected sample of older patients receiving cardiac rehabilitation. Methods: In 120 patients (88 men and 32 women, mean age 74.1 years ± SD 5.0) we assessed energy expenditure during the 6-min Walk Test (6mWT) before and after the rehabilitation using a portable system for direct calorimetry. Results: On the 6mWT performed after the rehabilitation patients significantly increased total energy expenditure (28.0. kcal ± SD 8.3 vs. 25.7. kcal ± SD 7.6, p<0.001), the distance walked (398. m ± SD 93 vs. 343. m ± SD 95, p<0.001) and, consequently, walking speed (1.11. m/s ± SD 0.26 vs. 0.95. m/s ± SD 0.26, p<0.001) while the metabolic cost of walking, i.e. the amount of energy used to move a body mass of 1. kg for a distance of 1. m, was significantly reduced (1.00. cal/kg/m ± SD 0.19 vs. 1.11. cal/kg/m ± SD 0.32, p<0.001). Conclusions: In older patients receiving cardiac rehabilitation the improvement of walking speed is associated with the improvement of walking economy. This might be a contributory factor to the favourable effects of physical activity interventions on physical performance measures.