Advanced age affects the individual leg mechanics of level, uphill, and downhill walking.

Advanced age brings biomechanical changes that may limit the uphill and/or downhill walking ability of old adults. Here, we investigated how advanced age alters individual leg mechanics during level, uphill, and downhill walking. We hypothesized that, compared to young adults, old adults would exhibit: (1) reduced trailing leg propulsive ground reaction forces (GRFs) and positive work rates during uphill walking, and (2) reduced leading leg braking ground reaction forces and negative work rates during downhill walking. We calculated the individual leg mechanical work performed by 10 old (mean±SD, age: 72±5 yrs) and 11 young (age: 26±5 yrs) adults walking at 1.25 m/s on a dual-belt force-measuring treadmill at seven grades (0° and ±3°, ±6°, ±9°). As hypothesized, old adults exhibited significantly reduced propulsive GRFs (e.g., -21% at +9°) and average trailing leg positive work rates (e.g., -26% at +9°) compared to young adults during both level and uphill walking. Old adults compensated by performing greater positive work than young adults during the subsequent single support phase. In contrast, we reject our second hypothesis. We found no differences in braking GRFs or negative work rates between old and young adults. However, old adults exhibited significantly reduced second peak perpendicular GRFs during downhill walking compared to young adults. Our findings most notably identify how advanced age may impair uphill walking ability and thus independence and quality of life.