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UBC Theses and Dissertations

The effect of altered oxygen tensions and exercise on flow-mediated dilation Wong, Lisa Elaine


Breathing hypoxia increases vasodilation during exercise, whereas breathing hyperoxia is known to increase vascular resistance. However, little is known about the effect of altered oxygen tensions on endothelial function, particularly following an acute bout of exercise in trained individuals. The purpose of our study was to assess the effects of constant load cycling and different levels of inspired oxygen (FIO₂) on endothelial function measured via flow-mediated dilation (FMD) in healthy trained men. It was hypothesized that exercising while breathing normoxic or hypoxic gas would improve FMD, whereas hyperoxic gas would not alter FMD. The study used a randomized crossover design. Thirteen healthy, recreationally active males (22±3 yrs) volunteered to participate. Subjects completed three graded exercise tests breathing either 16% O₂ (HYPO), 21% O₂ (NOX) or 100% O₂ (HYPER) to determine gas-specific maximal workload (Wmax). Subjects then performed three, 40-minute, constant-load cycling trials at 50% of the gas specific Wmax. Baseline FMD was measured during rest after 30 minutes of gas exposure and 30 minutes following each exercise trial, while breathing the experimental gas. No differences in baseline diameter, shear rate, time-to-peak dilation or FMD were found at rest or after exercise with any gas. Our data indicates that alterations in FIO₂ with and without exercise have no affect on vascular measures in young trained males. Exercise could have been more powerful on influencing the vasculature than changes in FIO₂. Training status and associated vascular remodeling and oxidant production could also account for the lack of change observed with FMD after exercise.

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