Changes in ventilatory threshold at high altitude: effect of antioxidants.
OBJECTIVE
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 mug 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.
Subudhi
Andrew W
AW
Department of Biology, University of Colorado at Colorado Springs, Colorado Springs, CO 80918, USA. asubudhi@uccs.edu
Jacobs
Kevin A
KA
Hagobian
Todd A
TA
Fattor
Jill A
JA
Muza
Stephen R
SR
Fulco
Charles S
CS
Cymerman
Allen
A
Friedlander
Anne L
AL
D000328:Adult; D000531:Altitude; D000704:Analysis of Variance; D000975:Antioxidants / Q000494:pharmacology*; D004311:Double-Blind Method; D005080:Exercise Test; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D008451:Maximal Voluntary Ventilation / Q000187:drug effects*; D010101:Oxygen Consumption / Q000502:physiology
D000975:Antioxidants