Muscle synergies in preparation to a step made with obstacle in elderly individuals

Background: to evaluate if multi-muscle synergies are comprised of flexible combinations of a small number of postural muscles to stabilize the center of pressure (cop) shift during preparation to making a step in the elderly (self-paced level stepping vs. obstacle crossing stepping). methods: electromyography (emg) signals of leg and trunk muscles were recorded. linear combination of integrated indices of muscle activity (m-modes) and their relationship to changes in the cop shift in the anterior-posterior (ap) direction were first determined. uncontrolled manifold (ucm) analysis was performed to determine the extent to which variance of the m-modes acted to produce a consistent change in the cop displacement. results: the elderly were capable of stabilizing the copap coordinate based on co-varied involvement of the m-modes. the synergy index (δv) changes in the elderly emerged later (100 ms prior to t0) and its magnitude was smaller as compared to that reported in younger persons. conclusions: our study reveals that aging is associated with a preserved ability to explore the flexibility of the m-mode compositions but a decrease ability to use multi-m-mode synergies following a predictable perturbation. © 2015 wang et al.; licensee biomed central.