Aging Ankles Trade Efficiency for Stability, and New Research Shows Exactly When the Switch Happens
Walking feels automatic to most people, something the body just handles. But inside every step is a finely tuned exchange between muscles, tendons, and the nervous system, and new research reveals that exchange starts to break down at the ankle as we get older. The body doesn’t simply fail. It compensates, and that compensation may help explain why older adults become more prone to fatigue, slower walking, and possibly falls.
Published in Gait & Posture, the study found that as people age, the ankle shifts from being a propulsion engine to acting more like a stabilizing brace. Rather than coordinating their timing efficiently, opposing ankle muscles begin firing together more during certain parts of each step, essentially locking the ankle joint during moments it should be free to push the body forward. It’s a bit like trying to drive with one foot on the gas and the other on the brake.
Tracking Ankle Mechanics Across 60 Years of Adulthood
Researchers drew on an existing dataset of walking data from 138 healthy adults, focusing on 107 participants who had complete muscle activity, motion, and force data. Participants ranged in age from 26 to 86, with an average age just over 56. Slightly more than half were women.
Each participant had previously walked barefoot along a 12-meter path at their own natural speed while equipment tracked everything: a 3D motion capture system recorded joint positions, force plates in the floor measured push forces, and skin electrodes recorded electrical signals from two key ankle muscles, the one along the front of the shin that lifts the foot and the large calf muscle that drives the foot downward for push-off. A statistical method sensitive enough to detect gradual change across adulthood was used to analyze the data continuously through each step, rather than snapping a single peak measurement. Because the study compared adults of different ages at a single point in time, it cannot prove how any one person’s ankle mechanics change year by year.
Aging Ankles Stiffen During the Wrong Part of Each Step
Walking has two distinct jobs. During the first half of each step, when the heel strikes the ground and the body’s weight rolls forward, the ankle absorbs impact and maintains balance. During the second half, when the heel lifts and the toes push off, the ankle generates the force that drives the body forward. These two jobs require very different things from the muscles involved.
In younger adults, the system is relatively efficient: muscles activate in a coordinated sequence, tendons store energy like a spring, and that energy powers the next step. With age, that coordination shifts in specific, measurable ways.
During the stance phase, when the foot is on the ground and bearing body weight, older adults showed greater simultaneous muscle activity from both the front-of-shin and calf muscles. This joint-stiffening pattern is a recognized nervous system response when sensory feedback from joints and muscles becomes less reliable. Prior research suggests those signals can become less precise with age, and the authors interpret this stiffening pattern as one way the nervous system may compensate. It’s a reasonable short-term fix for stability, but it comes with real costs.
Those costs showed up clearly in the push-off data. Despite greater calf muscle activity during the early part of the step, older adults produced lower pushing forces and weaker ankle drive in late stance. Their ankles also stayed in a more upward-tilted position during the critical push-off window. In short, the muscles were working harder but the ankle was delivering less, a sign that the body’s ability to translate muscular effort into forward motion deteriorates with age.
Notably, as older adults prepared for push-off, the simultaneous firing of both muscle groups actually decreased compared to younger adults. Researchers suggest this may reflect the ankle partially releasing its stiffening grip to allow some propulsion, but the push-off data shows that release isn’t enough to fully restore an efficient stride.
Source : https://studyfinds.com/your-ankles-change-your-walk-aging/
