Age and muscle strength mediate the age-related biomechanical plasticity of gait

Old compared with young adults walk with reduced ankle and increased hip mechanical output. We examined the idea that age, leg strength, or both are related to the age-related changes in mechanical output during gait.Healthy young (n = 32, age 21.5 years) and old adults (n = 32, age 76.8 years) participated in biomechanical gait analyses at 1.5 m/s and were also measured for maximal leg strength.Analysis 1 confirmed previous data as old compared with young adults walked with 50 % more hip positive work and 18 % less ankle positive work. Analysis 2 showed that leg strength did not affect gait kinetics in groups of subjects with similar ages. In a weak young and a strong old group, Analysis 3 showed that old adults still walked with 23 % greater hip positive work. The group by joint interaction in Analysis 4 was suggestive of an even greater reliance on hip and less reliance on ankle work in weak compared with strong old adults.Age and leg strength both contribute to the age-related changes in mechanical output during gait. Exercise prescription, normally targeting the knee extensors, should also involve ankle and hip muscles.