Researchers in Australia say they have pinpointed a specific mechanical shift behind a familiar complaint of aging: walking that grows slower, more tiring and less steady. The culprit, according to a new gait study, is not simply weaker legs but a change in how the nervous system controls the ankle with every step.
The study, led by Flinders University's Caring Futures Institute in collaboration with the University of Canberra, analyzed detailed movement data from 107 healthy adults ranging in age from 26 to 86. Using motion capture to track the ankle and surrounding muscles through a full walking cycle, the team found older participants increasingly relied on "co-contraction" — activating opposing muscles around the ankle at the same time, which stiffens the joint the instant the foot strikes the ground.
A trade-off between safety and speed
That stiffening improves stability and helps prevent the ankle from buckling, but it comes at a cost. "Stiffening the joint makes walking safer, but it also means the muscles are working harder without generating as much forward movement," said lead author Dr. Cody Lindsay, a sport and exercise technology researcher at Flinders, in the university's release describing the findings. Older adults in the study also generated less push-off power with each stride, producing shorter steps and slower overall walking speed. The paper, "Ageing alters ankle mechanics and muscle co-contraction patterns across the gait cycle," was published in the journal Gait & Posture.
The pattern reflects what the researchers describe as a "safety-first" recalibration by the nervous system rather than simple muscle decline. Co-author Associate Professor Maarten Immink, who leads Flinders' Active Lives Research Program, said the nervous system is "compensating for age-related changes by favoring stability over performance" — a trade-off that, over years, contributes to the reduced walking efficiency and elevated fall risk long observed in older populations.
The nervous system adopts a safety-first approach, compensating for age-related changes by favoring stability over performance.
Associate Professor Maarten Immink, Flinders University
Falls among adults over 65 are a leading cause of injury-related hospitalization worldwide, and researchers have long sought to distinguish which specific declines — strength, balance, reaction time, or gait mechanics — drive that risk, since interventions differ depending on the cause. By isolating ankle co-contraction and push-off power as measurable culprits, the Flinders-Canberra team said their data point toward targeted fixes rather than generic "stay active" advice, a finding also summarized independently by EurekAlert's release of the study.
The authors recommend balance-focused exercise such as tai chi, along with lower-leg strengthening and coordination drills, as ways older adults might counteract the stiffening pattern before it worsens. The team said its next step is testing whether such targeted training can measurably restore push-off power and stride length in older adults, rather than only slowing further decline.
