Neuromechanical response of the upper body to unexpected perturbations during gait initiation in young and older adults.

The age-related reduction in trunk movement could indicate a more rigid behaviour of the upper body employed by older compared to young individuals in response to unexpected perturbations preceding the initiation of stepping. Older adults' delayed activation of thoracic muscles could suggest impaired reactive mechanisms that may potentially lead to a fall in the early stages of the gait initiation.