Advanced Age Redistributes Positive but Not Negative Leg Joint Work during Walking

Introduction Advanced age brings a distal-to-proximal redistribution of positive joint work during walking that is relevant to walking performance and economy. It is unclear whether negative joint work is similarly redistributed in old age. Negative work can affect positive work through elastic energy return in gait. We determined the effects of age, walking speed, and grade on positive and negative joint work in young and older adults. Methods Bilateral ground reaction force and marker data were collected from healthy young (age 22.5 years, n=18) and older (age 76.0 years, n=22) adults walking on a split-belt instrumented treadmill at 1.1, 1.4, and 1.7 m/s at each of three grades (0, 10, and -10%). Subjects also performed maximal voluntary eccentric, isometric, and concentric contractions for the knee extensors (120, 90, 0°/s) and plantarflexors (90, 30, 0°/s). Results Compared to young adults, older adults exhibited a distal-to-proximal redistribution of positive leg joint work during level (p

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