Imagine stepping on a moving target while trying to maintain balance. Now, picture how tricky it would be if you were older and your body wasn’t as quick and stable as it once was. In a targeted stepping task, researchers compared the stepping performance of young and older adults. Surprisingly, they found that both groups faced similar accuracy-speed-stability trade-offs, meaning they had to make compromises in one area to excel in another. This challenges the assumption that older adults struggle more with these trade-offs due to declining sensorimotor function. In fact, sensorimotor function didn’t explain the differences in trade-offs between individuals. The research suggests that while older adults may be less accurate and stable overall, their unique accuracy-stability trade-off could shed light on why their accuracy is lower than that of younger adults.

IntroductionStepping accuracy, speed, and stability are lower in older compared to young adults. Lower stepping performance in older adults may be due to larger accuracy-speed-stability trade-offs because of reduced ability to simultaneously fulfill these task-level goals. Our goal was to evaluate whether trade-offs are larger in older compared to young adults in a targeted stepping task. Since sensorimotor function declines with age, our secondary goal was to evaluate whether poorer sensorimotor function was associated with larger trade-offs.MethodsTwenty-five young (median 22 years old) and 25 older (median 70 years old) adults stepped into projected targets in conditions with various levels of accuracy, speed, and stability requirements. We determined trade-offs as the change in performance, i.e., foot placement error, step duration, and mediolateral center of pressure path length, between each of these conditions and a control condition. To assess age-related differences in the magnitude of trade-offs, we compared the change in performance between age groups. Associations between trade-offs and measures of sensorimotor function were tested using correlations.ResultsWe found an accuracy-speed and an accuracy-stability trade-off in both young and older adults, but trade-offs were not different between young and older adults. Inter-subject differences in sensorimotor function could not explain inter-subject differences in trade-offs.ConclusionAge-related differences in the ability to combine task-level goals do not explain why older adults stepped less accurate and less stable than young adults. However, lower stability combined with an age-independent accuracy-stability trade-off could explain lower accuracy in older adults.

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