ANTIOXIDANT STATUS AND INDEXES OF OXIDATIVE STRESS DURING CONSECUTIVEDAYS OF EXERCISE

We tested whether consecutive days of prolonged submaximal exercise wo uld result in oxidant stress sufficient to alter blood antioxidant pro files, progressively change and exhaust blood and plasma antioxidants, and damage RNA. Eleven moderately trained males (24.3 +/- 1.1 yr) exe rcised 90 min at 65% peak 0, uptake on a cycle ergometer for 3 consecu tive days. During day 1 exercise, blood reduced glutathione (GSH) decl ined 55 +/- 10% and oxidized glutathione (GSSG) increased 28 +/- 7% wi thin 15 min. Total blood glutathione did not significantly change duri ng exercise. GSH levels returned to baseline after 15 min of recovery. On day 3, preexercise GSH and GSSG levels were not significantly diff erent from day 1 preexercise values; essentially similar results were obtained during exercise and recovery. During day 1 exercise, plasma t otal ascorbate (ascorbate + dehydroascorbate) increased from 53.8 +/- 9.3 to 59.0 +/- 11.3 muM, and percent reduced ascorbate increased from 77.6 +/- 9.3 to 87.3 +/- 9.7%. During day 3 exercise, plasma ascorbat e changes were similar to those on day 1. Plasma vitamin E did not cha nge due to exercise on either day 1 or 3. RNA adducts, urinary 8-hydro xyguanosine, did not change significantly due to exercise. Observed in creases in GSH oxidation indicate the presence of oxidant stress durin g prolonged submaximal exercise. Similar redox changes on consecutive days of exercise, with recovery to preexercise values within 15 min, i ndicate no evidence of persistent or cumulative exercise effects on bl ood glutathione redox status. We conclude that young healthy men are p rotected from reactive oxidant species formation during exercise, ther e is no evidence of persistent or cumulative effects of exercise on bl ood antioxidants, and oxidant stress during single or consecutive bout s of prolonged submaximal exercise is insufficient to result in damage to RNA.