Journal
MEDICINE AND SCIENCE IN SPORTS AND EXERCISE
Volume 38, Issue 8, Pages 1425-1431Publisher
LIPPINCOTT WILLIAMS & WILKINS
DOI: 10.1249/01.mss.0000228939.32281.39
Keywords
hypoxia; free radical; VO2max; anaerobic threshold; lactate threshold
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Purpose: To investigate the effects of prolonged hypoxia and antioxidant supplementation on ventilatory threshold (VT) during high-altitude (HA) exposure (4300 m). Methods: Sixteen physically fit males (25 +/- 5 yr; 77.8 +/- 8.5 kg) performed an incremental test to maximal exertion on a cycle ergometer at sea level (SL). Subjects were then matched on VO2peak, ventilatory chemosensitivity, and body mass and assigned to either a placebo (PL) or antioxidant (AO) supplement group in a randomized, double-blind manner. PL or AO (12 mg of beta-carotene, 180 mg of alpha-tocopherol acetate, 500 mg of ascorbic acid, 100 mu g of selenium, and 30 mg of zinc daily) were taken 21 d prior to and for 14 d at HA. During HA, subjects participated in an exercise program designed to achieve an energy deficit of approximately 1400 kcal-d-1. VT was reassessed on the second and ninth days at HA (HA2, HA9). Results: Peak power output (W-peak and VO2peak decreased (28%) in both groups upon acute altitude exposure (HA2) and were unchanged with acclimatization and exercise (HA9). Power output at VT (W-VT) decreased from SL to HA2 by 41% in PL, but only 32% in AO (P < 0.05). WVT increased in PL only during acclimatization (P < 0.05) and matched AO at HA9. Similar results were found when VT was expressed in terms of % W-peak and % VO2peak. Conclusions: VT decreases upon acute HA exposure but improves with acclimatization. Prior AO supplementation improves VT upon acute, but not chronic altitude exposure.
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