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UBC Theses and Dissertations

The effects of strenuous exercise on cardiovascular function in healthy humans Coté, Anita Theresa


RATIONALE: Strenuous exercise has been shown to elicit transient reductions in ventricular systolic and diastolic function, as well as impaired autonomic function. The effects of training status and sex on the development of these acute alterations are not known. The aim of these studies was to examine vascular adjustments, cardiac mechanics and autonomic function as the result of strenuous exercise in healthy, endurance-trained (ET) and normally active (NA), males and females. Statistical significance was set at p < 0.05. The first investigation explored sex differences in the cardiovascular response to an ultra-marathon in 25 runners. Ventricular function was reduced similarly in men and women. Novel associations of life-time ultra-marathons and degree of longitudinal strain were found, demonstrating the absence of cumulative stress on the heart with long-term prolonged strenuous exercise. The second investigation assessed ventricular function following high-intensity interval exercise (HIT) in 39 men and women. Changes in cardiac mechanics were not differentiated by training status, however, lower baseline arterial stiffness was associated with twist augmentation. Men demonstrated greater reductions in contractility and higher arterial elastance post-exercise than women. The third investigation assessed autonomic function following HIT and orthostatic stress in 33 men and women. Throughout the intervention, women displayed greater strain, strain rate, and baroreflex sensitivity, but there were no interactions of condition by sex. Autonomic function decreased to a greater degree in ET, but also improved most rapidly in recovery. Thus, it would appear that the cardiac and autonomic stability of ET and women during an orthostatic challenge is not compromised in the face of HIT. The fourth investigation analyzed post-exercise hypotension (PEH) following HIT in 21 individuals. Hypotension occurred similarly in all individuals however, men experienced greater reductions in stroke volume. These findings suggest men engage a different mechanism of PEH compared to women. The fifth investigation explored cognitive function in recovery from HIT. Cognition was improved post-exercise and persisted for four hours post-exercise. SUMMARY: Together, these studies provide novel findings pertaining to the effects of sex and training status on the cardiovascular responses to strenuous exercise.

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