Influence of exercise intensity on endogenous oxidative stress and antioxidant capacity

Introduction: Regular physical activity and exercise are commonly used as an effective treatment for numerous diseases and general poor health. While the health benefits of engaging in regular physical activity are well known, an ideology gaining momentum in recent years has been that certain intensities may elicit a negative physiological effect through exercise induced oxidative stress (EIOSI). While previous research has paved the way to understanding EIOS stress at a superficial level, the relationship between exercise sub-components such as intensity and EIOS remain far more elusive. Therefore, the aim of the current study was to examine the influence of exercise intensity on EIOS including antioxidant capacity. Methods: Non-smoking, untrained 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 (VO₂max). One week later, participants undertook 5 minute cycling bouts at 40% VO ₂max, 55% VO₂max, 70% VO₂max, 85% VO₂max and 100% VO₂max, with a passive 12 minute rest between stages. Measures of EIOS including biological antioxidant capacity (BAP) and reactive oxygen metabolites (dROM), and heart rate, VO₂, blood lactate and physical exertion were assessed at rest and immediately following each exercise stage. Significant (p<0.05) comparisons between exercise bouts were compared using repeated measures ANOVA and post-hoc painwise comparisons with a Bonferroni correction. Results: Increasing exercise intensity significantly augmented heart rate (P<0.001), VO₂ (p<0.001), blood lactate (p<0.001) and physical exertion (p