Effects of age and fatigue on human gait

When healthy humans walk in a real-life environment, there could be many distractions that can perturb walking. The ability to adjust walking to such perturbations can prevent a loss of balance, trips, and falls. Aging affects the ability to adjust gait to perturbations. One type of perturbation is fatigability that limits the capacity to allocate internal resources and may require age-specific adjustments in gait. This thesis has examined whether and how healthy older adults who do not otherwise report being tired, adjust their gait to fatigability. Firstly, we reviewed studies and concluded that the underlying mechanism of fatigability’s effect on older adults’ gait remains unclear. Therefore, we developed an experimental model in which older and younger adults walked on a treadmill before and after induced mental (demanding mental tasks) and muscle fatigability (repetitive sit-to-stand – rSTS). We measured the strides outcomes and its variability, dynamics features of gait, and neuromuscular control during walking. We also examined the muscle activation during rSTS and maximal voluntary isometric force (MVIF) before and after rSTS to verify the suitability of rSTS in inducing muscle fatigability. Surprisingly, we found minimal effects of muscle and mental fatigability on stride outcomes and gait variability. Mental performance fatigability appears to affect gait only during dual-task walking. Such minimal effects generated by muscle fatigability were accompanied by only subtle changes induced by rSTS on muscle activation and MVIF. However, rSTS induced age-specific changes in the neuromuscular control, which might have compensated for fatigue to maintain older adults’ gait performance.