Effects of age and task difficulty on neuromuscular and corticomuscular determinants of walking balance

Walking balance determines mobility and independence. Healthy aging impairs walking balance, causing slow gait, reduced ability to respond to perturbations while walking, and balance loss when turning. Such impairments can go unnoticed when one is relatively young and walks on an unperturbed level surface.

This thesis of Andréia Abud da Silva Costa examined the effects of age and walking task difficulty on walking balance. Walking was challenging as participants walked on a low-lying narrow board, which required precise placement of the foot.

First, we determined the effects of three board widths and three arm positions on balance while walking with and without a concomitant cognitive task. Second, we compared young and older adults’ muscle activation on two walking surfaces, and while changing arm position and cognitive load. Lastly, we examined corticomuscular and intermuscular coherence, indexes of the brain's control of muscle activity, when walking on the floor, a narrow ribbon, and a narrow board.

We observed that older adults’ walking balance was most affected by the narrowest beam width (6 cm) and crossed arms. The cognitive task did not affect walking balance. Older adults used fewer combinations (synergies) of muscle activity. Cognitive task increased the number of muscles activated and their activation level within a synergy while arm-crossing reduced the number of recruited muscle synergies.

Age and walking difficulty increased brain involvement in the neural control of walking balance. Age-related declines in walking balance are thus clearer in challenging walking tasks, possibly due to compromised cognitive resource-sharing due to older adults’ less automated gait.