Mechanical Work and Pendulum-Like Mechanism Of Walking: A Comparison Between Children and Adults at Self-Selected Speed

Children spend more energy walking than adults, and younger children are less efficient at producing positive muscular work. Even comprehending these mechanical determinants at fixed speeds, differences of pendulum-like mechanism and mechanical work at self-selected speeds between children and adults are unknown. Analyzing these mechanical determinants in self-selected conditions can provide a more applied framework for health, given that walking speed is a crucial indicator of health. Thus, we sought to compare spatiotemporal, Recovery, and mechanical work parameters between children and adults at self-selected walking speed. Also, we evaluated the locomotor rehabilitation index (how the self-select speed is close to optimal walking speed) based on the Froude number. Thirteen children aged 6 to 12 years and twenty-four adult subjects aged 18 to 64 walked at their self-selected walking speed while their movements were three-dimensionally registered (10m, corridor). Children walked at self-selected speed, presenting a shorter stride length and a higher stride frequency than adults, resulting in a similar self-selected walking speed. The pendulum-like mechanism observed directly (Recovery) or indirectly (locomotor rehabilitation index) was better in children than adults. This higher pendulum-like Recovery results in lower external mechanical work for children, though vertical and forward counterparts of external work were similar between groups. Interestingly, the similar results from the Recovery and locomotor rehabilitation index indicate the practical usage of the former variable in clinical setups. The pendulum-like mechanism improved at self-selected speed in children reinforces the rationale that lower economy in children is related mainly to muscular efficiency than the transmission efficiency factors.