The influence of voluntary movement dynamics on postural stability borders and balance recovery strategies

Falls are the number one cause of unintentional injury, and often occur during tasks such as bending and reaching. My thesis examined how the dynamic features of an ongoing task influenced one’s ability to maintain and recover balance. In study one, I conducted experiments and mathematical modeling to show there was a tradeoff between the frequency and amplitude of heel-toe rocking movements that can be performed without losing balance. The central nervous system (CNS) must account for this tradeoff in planning stable movements. In study two, I conducted experiments to perturb participants’ balance at different phases of the rocking cycle, and found that, when the initial position was constant, the velocity at the time of the perturbation influenced the kinematics and muscle activities associated with the recovery response. This indicated an ability of the CNS to adapt the postural response to the nature of the ongoing task.