Neuromechanics of postural responses to balance loss

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Falls are the leading cause of unintentional injuries to older adults and the third-most common cause of worker's injury compensation claims in Canada. To avoid falls and injuries, humans rely on a repertoire of postural responses to balance loss, classified as: 1) balance recovery responses (e.g., stepping or grasping handrails) to avoid falls, and 2) fall protective responses (e.g., upper limb bracing) to reduce impact to body parts during a fall. Our understanding of how humans control postural responses to balance loss is limited. Postural responses to balance loss are much faster than voluntary movements (e.g., reaching after hearing a sound), and involve higher rates of muscle force and joint torque production to halt the momentum of the centre of mass (COM) and torso. These fundamental differences mean that knowledge from voluntary movements applies poorly to the control of postural responses to balance loss. We need a deeper understanding of how humans control postural responses that considers the complexity of individual factors (e.g., age or sex), their task (e.g., carrying a load or walking), and their environment (e.g., lighting or patterned surfaces), to inform evidence-based strategies for fall and injury prevention. My long-term goal is to generate comprehensive models of how the nervous and musculoskeletal systems interact (i.e., neuromechanics) to control postural responses to balance loss, and examine how these responses depend on the individual, the movement task, and the environment, to guide fall and injury prevention strategies. For the proposed DG, my team will run innovative lab experiments to identify how individual factors (e.g., age, sex, strength, proprioception, and landing position) govern the control of fall protective responses. We will also test the effect of tasks on the control of balance recovery and fall protective responses, focusing on carrying loads and other concurrent tasks (walking or talking), age, and sex. Regarding environmental factors, we will test the effect of lighting conditions (ambient lighting, versus head-mounted or floor/handrail-mounted lighting) and the interacting effects of age, sex, and distractions on the control of balance recovery responses. We will quantify the effectiveness of mechanical control with COM/torso momentum (using motion capture), and neural aspects of control with muscle activation and effort (using electromyography). My team's results will provide a foundation to explore future lines of inquiry on the interacting effects of other individual, task and environmental factors on the control of postural responses, such as lighting systems and sleep deprivation, or load carrying and muscle fatigue. In addition to generating new and improving existing models on the control of postural responses, findings from this DG will guide the design of best practices for carrying loads and of lighting systems, for avoiding falls and injuries in the home, community or at work.