Initial posture explains variability in kinematic responses to perturbations of standing

We combined experiments and predictive simulations to explain the large intra-subject variability observed in the kinematic responses to backward perturbations of standing balance when randomly administered within a set of multi-directional support-surface translations and rotations. We found that centre-of-mass location at perturbation onset has an important contribution to the variability in kinematic response. Our results suggest that variability in initial posture induced by postural sway, especially in older adults, can have an important impact on the kinematic response to a perturbation and hence on stability during the response.