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 β-carotene, 180 mg of α-tocopherol acetate, 500 mg of ascorbic acid, 100 μg 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 (Wpeak) and VO2peak decreased (28%) in both groups upon acute altitude exposure (HA2) and were unchanged with acclimatization and exercise (HA9). Power output at VT (WVT) 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 % Wpeak 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.
1University of Colorado at Colorado Springs, Colorado Springs, CO; 2Veterans Affairs Palo Alto Health Care System, Palo Alto, CA; 3University of Miami, Miami, FL; 4University of Massachusetts, Amherst, MA; 5University of California Berkeley, Berkeley, CA; and 6U.S. Army Research Institute of Environmental Medicine, Natick, MA
Address for correspondence: Andrew W. Subudhi, Ph.D., Department of Biology, University of Colorado at Colorado Springs, 1420 Austin Bluffs Parkway, Colorado Springs, CO 80918; E-mail: email@example.com.
Submitted for publication November 2005.
Accepted for publication March 2006.