Lower extremity power training improves healthy old adults' gait biomechanics

Purpose: Age-related slowing of gait speed predicts many clinical conditions in later life. We examined the kinematic and kinetic mechanisms of how lower extremity power training increases healthy old adults' gait speed. Methods: We randomly allocated old adults to a training (age 74.3 y, 9 males, 6 females) and a control group (age 73.6 y, 3 males, 4 females) and compared the biomechanics of habitual and fast gait before and after 16 sessions (8 weeks) of lower extremity power training. Results: Training increased maximal leg press load by similar to 40% (P < 0.05) and maximal voluntary force in five groups of leg muscles by similar to 32% (P < 0.05) in the training group. Training vs. control tended to increase habitual (10.8 vs. 7.6%) and fast gait speed (17.6 vs. 9.0%; all P < 0.05) more. In the training group only, these increases in gait speed correlated with increases in stride length (habitual: r(2) = 0.84, fast: r(2) = 0.89). Training made old adults' gait more erect: hip and knee extension increased in the stance phase of gait. Training increased ankle joint positive work by 3.3 J (control: -0.4 J, Group by Time interaction: P < 0.05), which correlated r(2) = 0.58 and r(2) = 0.67 with increases in habitual and fast gait speed without changes in hip and knee joint powers. Conclusion: Increases in leg muscle power increased healthy old adults' gait speed through correlated increases in stride length and ankle plantarflexor work generation.