NO EVIDENCE OF OXIDATIVE STRESS OR DNA DAMAGE FOLLOWING THE BRUCE GXT PROTOCOL

Abstract

Graded exercise tests (GXT) performed to exhaustion have been suggested to induce oxidative stress. PURPOSE: This study investigated the effect of the Bruce GXT protocol on markers of oxidative stress and DNA damage. METHODS: Twenty healthy, untrained males (age 27 ± 5 years: BMI 24.7 ± 3.3), with no history of nutritional supplementation, were placed on a controlled, low antioxidant diet for 3 days prior to and 24 hours following exercise. Venous blood samples were collected on four occasions: after a 12-hour fast immediately before exercise immediately after exercise, and following 24 hours of recovery. Samples were analyzed for serum concentrations of thiobarbituric acid reactive substances (TBARS), erythrocyte reduced to oxidized glutathione ratios (GSH:GSSG), and leukocyte DNA damage (COMET). Urine was collected immediately before and 1 hour after exercise for 8-hydroxydeoxyguanosine (8-OHdG) analysis. RESULTS: Dietary antioxidant intakes were below USRDA recommendations (< 1 mg/d b-carotene, 7 ± 3 mg/d ascorbic acid, and 73 ± 22 mg/d a-tocopherol). Physiological responses to exercise were indicative of exhaustion (RER 1.25 ± 0.1: VO2peak 45 ± 8 ml/kg/min). However, repeated measures ANOVA did not detect significant changes in GSG:GSSG (1244 ± 425), TBARS (0.41 ± 0.10 mM), COMET (4.1 ± 3.1), or 8-OHdG (2.7 ± 1.2 mg/mg creatinine) across time (p > .20). CONCLUSION: Results suggest that the Bruce GXT protocol did not induce a measurable oxidative stress in healthy, untrained individuals eating a low antioxidant diet. Sponsor: Pharmanex, LLC.