Aging and running experience affects the gearing in the musculoskeletal system of the lower extremities while walking

The aims of this study were to investigate whether older adults modify their walking mechanics to compensate for the degeneration in their muscle-tendon units (MTUs), and to examine whether running has a beneficial effect on walking mechanics in younger and older adults. The investigation was conducted on 30 older and 19 younger adults divided into two subgroups: runners versus non-active. In previous studies we documented that older adults had lower leg-extensor muscle strength and tendon stiffness compared to younger. Runners and non-active subjects had similar MTU capacities. In this study we analysed walking kinematics and kinetics (1.6 m/s) from the same subjects. Older adults showed a lower gear ratio (ratio between moment arm of the ground reaction force and moment arm of muscle) at the triceps surae MTU during the initial and mid part of ground contact, lower average horizontal forces and lower average ankle joint moment during ground contact compared to younger (p<0.05). Compared to non-active subjects, runners had a lower gear ratio at the quadriceps femoris MTU during the initial and final part of ground contact, lower average horizontal forces and lower maximal knee joint moment during ground contact independent of the subject's age (p<0.05). We concluded that the older adults modify the gearing at the ankle joint in order to adjust the task effort to the reduced triceps surae muscle strength. It appears, further, that runners walked more effectively from a mechanical standpoint compared to non-active subjects, which suggests that runners may be able to transfer motor adaptation from running to walking even in old age.