Changes in Ventilatory Threshold at High Altitude: Effect of Antioxidants

Andrew W. Subudi, University of Coloradoat ColoradoSprings, ColoradoSprings, CO
Kevin A. Jacobs, Veterans Affairs PaloAlto Health Care System, Palo Alto, CA
Todd A. Hagobian, Veterans Affairs PaloAlto Health Care System, Palo Alto, CA
Jill A. Fattor, Universityof California Berkeley, Berkeley, CA
Stephen R. Muza, U.S. Army Research Institute of Environmental Medicine, Natick, MA
Charles S. Fulco, U.S. Army Research Institute of Environmental Medicine, Natick, MA
Allen Cymerman, U.S. Army Research Institute of Environmental Medicine, Natick, MA
Anne L. Friedlander, Veterans Affairs PaloAlto Health Care System, Palo Alto, CA,

Article comments

Copyright © 2006 American College of Sports Medicine. This is a non-final version of an article published in final form in Medicine and Science in Sports and Exercise. The definitive version is available at http://dx.doi.org/10.1249/01.mss.0000228939.32281.39.

NOTE: At the time of publication, the author Todd A Hagobian was not yet affiliated with Cal Poly.

Abstract

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 kcald^-1. VT was reassessed on the second and ninth days at HA (HA2, HA9).
Results: Peak power output (W_2peak) and VO_2peak 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). W_VT 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 % VO_2peak.
Conclusions: VT decreases upon acute HA exposure but improves with acclimatization. Prior AO supplementation improves VT upon acute, but not chronic altitude exposure.