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

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 (OR, n = 15 (5F)), or did not (ONR, n = 25 (17F)), proximally redistribute joint work using a redistribution ratio (RR), where OR had an RR > 0.79 (Young mean RR + 1 SD) and ONR had an RR ≤ 0.79. Contrary to our hypothesis, CoW was not different between OR (0.105 ± 0.019 ml·kg⁻¹·min⁻¹) and ONR (0.106 ± 0.016 ml·kg⁻¹·min⁻¹), while moderate-to-large effects for CoW were observed for both ONR (P = 0.035, d = 0.83) and OR (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 OR and ONR, but OR was comprised predominantly of male participants suggesting sex specific factors for the gait shift should be queried.