Doctor of Medicine and Doctor of Philosophy (MDPhD)
Autonomic dysfunction following spinal cord injury: mechanisms, novel treatments, and clinical reality
Individuals with spinal cord injury (SCI) are at greatly increased risk of cardiovascular disease (CVD). This is likely due to physical inactivity and impaired sympathetic control of the heart and blood vessels, resulting in cardiovascular dysfunction. Cardiovascular dysfunction in individuals with SCI is associated with injury level, whereby individuals with higher lesions exhibit greater dysfunction. In people without SCI, cardiac dysfunction predicts CVD. The studies that have investigated cardiac indices in individuals with SCI tend to agree that cardiac atrophy and impaired systolic function occur following SCI. Physical activity is a key method to decrease CVD risk and improve cardiac function, yet few studies have examined the relationship between cardiac function and physical activity in individuals with SCI. Those that have investigated this relationship have used subjective measures of physical activity. The current guidelines for physical activity participation for individuals with SCI were based on a systematic review of the evidence on the benefits of physical activity, yet there was inadequate evidence to prescribe activity intensity and duration to improve cardiovascular health in this population. Individuals with SCI also experience numerous barriers and facilitators to physical activity participation that affect their ability to meet the guideline recommendations. The objectives of this thesis, therefore, were: 1) to objectively measure physical activity in individuals with SCI, using wrist-worn accelerometry during a six-day physical activity monitoring period, and to evaluate the utility of group based wrist accelerometry cut-points to estimate physical activity intensity by comparing MVPA determined by individual cut-points to MVPA determined by group-based cut-points; 2) to determine the relationship between objectively measured physical activity and cardiac structure and function in individuals with SCI across a range of injury levels, and 3) to explore the barriers and facilitators to physical activity participation experienced by individuals with SCI during a six-day physical activity monitoring period.