Neuromuscular and behavioural influences on balance and falls

Falls are the number one cause of accidental injury and exert an especially heavy toll on the elderly. Most falls involve a common sequence of events. First, a particular event results in loss of balance. Second, there is a failed attempt at recovering balance, and finally, once the fall is "recognized" to be inevitable, attempts may be made to lessen its severity. My thesis research focuses on neuromuscular and behavioural aspects of balance maintenance and protective responses during falls. In Chapter 2 and 3, I describe efforts to develop and apply a novel technique to determine how risk for imbalance during daily activities depends on behavioural versus neuromuscular factors. Specifically, I developed the “Reach Utilization Test” to determine whether the tendency to approach imbalance is different between young and elderly women who resided either in nursing homes (Chapter 2) or in the community (Chapter 3). In Chapters 4 to 7, I focus on the measurement and analysis of protective responses during sideways falls. In Chapter 4, I describe the results of experiments to determine whether unexpected sideways falls in young adults elicit a common sequence of responses that might protect against hip fracture. I used a novel experimental paradigm which challenged participants to focus on maintaining balance after experiencing a single large perturbation, which in the vast majority of cases elicited a sideways fall. In Chapter 5, I describe the results of experiments to test whether the ability of humans to alter their body configuration during the fall depends on the time when the response is initiated. I hypothesized that a critical time window exists, beyond which one is unable to avoid hip impact. In Chapter 6, I describe the results of experiments to determine whether individuals are able to accurately recall the details of their falls. I addressed this question by interviewing young adults immediately after they experienced an unexpected sideways falls. Finally, in chapter 7, I describe results from a modelling study to address how fall severity depend on the cause of the fall (slip vs. trip).