A distal-to-proximal shift is not a requisite mechanism for greater metabolic cost of walking in older adults.

Abstract

A greater metabolic cost of walking (CoW) is well-documented in older compared with young adults and is likely a catalyst for age-related mobility loss. Proximal redistribution of joint work during gait has been suggested as a contributor to greater CoW in aging. However, evidence to support this link is limited. We collected overground gait kinematics and kinetics as well as metabolic data during a 7-minute treadmill walk (7MTW) in 15 young (30-40 years, 8F) and 40 older (70-80 years) adults. We then separated the older adults into two groups based on whether they did (O_R, n = 15 (5F)), or did not (O_NR, n = 25 (17F)), proximally redistribute joint work using a redistribution ratio (RR), where O_R had an RR > 0.79 (Young mean RR + 1 SD) and O_NR had an RR ≤ 0.79. Contrary to our hypothesis, CoW was not different between O_R (0.105 ± 0.019 ml·kg^-1·min^-1) and O_NR (0.106 ± 0.016 ml·kg^-1·min^-1), while moderate-to-large effects for CoW were observed for both O_NR (P = 0.035, d = 0.83) and O_R (P = 0.106, d = 0.70) when compared to young (0.089 ± 0.013 ml·kg^-1·min^-1). These results suggest that the distal-to-proximal shift does not explain the greater CoW in older adults and further that restoring a "youthful" gait pattern may not address the problem of a greater CoW in older adults. Group characteristics such as age or preferred walking speed did not differ between the O_R and O_NR, but O_R was comprised predominantly of male participants suggesting sex specific factors for the gait shift should be queried.