Exercise is inherently linked with the production of reactive oxygen and nitrogen species (RONS) resulting in augmented oxidative stress post-exercise. Antioxidant supplements have been proposed to reduce exercise-induced oxidative stress, but this alleviation can potentially negate signalling pathways mediated by RONS. This thesis presents novel findings on the consumption of antioxidant supplements and the effects of habitual supplementation on exercise-induced oxidative stress following a cycling sportive in recreational cyclists (chapters 1 and 2). Consumption of antioxidant supplements is not associated with age, cycling experience or weekly training hours; nor do they provide additional protection in reducing oxidative stress on completion of a cycling sportive. The final two experimental chapters assessed the effect of habitual supplementation on basal levels of endogenous antioxidants and the oxidative stress response to steady-state cycling (chapter 4). And the effect of polyphenol supplementation on cycling recovery, assessed by markers of oxidative stress, inflammation and cycling performance in trained cyclists (chapter 5). Habitual supplementation did not affect baseline concentrations of superoxide dismutase-1 (SOD1), superoxide dismutase-2 (SOD2) or glutathione peroxidase-1 (GPx-1); nor the oxidative stress response to steady-state cycling. Supplementation with a polyphenol drink did not attenuate exercise-induced oxidative stress, inflammation, or improve cycling performance compared to placebo
