Influence of exercise intensity on systemic oxidative stress and antioxidant capacity.

The aim of the current study was to examine the influence of exercise intensity on systemic oxidative stress (OS) and endogenous antioxidant capacity. Non-smoking, sedentary healthy adult males (n = 14) participated in two exercise sessions using an electronically braked cycle ergometer. The first session consisted of a graded exercise test to determine maximal power output and oxygen consumption (VO(2max)). One week later, participants undertook 5-min cycling bouts at 40%, 55%, 70%, 85% and 100% of VO(2max), with passive 12-min rest between stages. Measures of systemic OS reactive oxygen metabolites (dROM), biological antioxidant potential (BAP), heart rate (HR), VO(2), blood lactate and rating of perceived exertion were assessed at rest and immediately following each exercise stage. Significant (P<0·05) differences between exercise bouts were examined via repeated measures ANOVA and post hoc pairwise comparisons with Bonferroni correction. Increasing exercise intensity significantly augmented HR (P<0·001), VO(2) (P<0·001), blood lactate (P<0·001) and perceived exertion (P<0·001) with no significant effect on dROM levels compared with resting values. In contrast, increasing exercise intensity resulted in significantly (P<0·01) greater BAP at 70% (2427 ± 106), 85% (2625 ± 121) and 100% (2651 ± 92) of VO(2max) compared with resting levels (2105 ± 57 μmol Fe(2+)/L). The current results indicate that brief, moderate-to-high-intensity exercise significantly elevates endogenous antioxidant defences, possibly to counteract increased levels of exercise-induced reactive oxygen species. Regular moderate-to-high-intensity exercise may protect against chronic OS associated diseases via activation, and subsequent upregulation of the endogenous antioxidant defence system.