Acetazolamide does not alter endurance exercise performance at 3,500-m altitude

Abstract

Acetazolamide (AZ) is a medication commonly used to prevent acute mountain sickness (AMS) during rapid ascent to high altitude. However, it is unclear whether AZ use impairs exercise performance; previous literature regarding this topic is equivocal. The purpose of this study was to evaluate the impact of AZ on time trial (TT) performance during a 30-hr exposure to hypobaric hypoxia equivalent to 3500 m altitude. Ten men (sea-level VO₂peak: 50.8 ± 6.5 ml·kg^-1·min^-1; BF %: 20.6 ± 5.2%) completed two, 30-hr exposures at 3500 m. In a crossover study design, subjects were given either 500 mg/day of AZ or a placebo. Exercise testing was completed 2-hr and 24-hr after ascent and consisted of 15-min steady state treadmill walking at 40-45% sea-level VO₂peak, followed by a 2-mile self-paced, treadmill TT. AMS was assessed after ~12 and 22-hr at 3500 m. The incidence of AMS decreased from 40% with placebo to 0% with AZ. Oxygen saturation was higher (P < 0.05) in AZ vs placebo trials at the end of the TT after 2-hr (85 ± 3% vs 79 ± 3%) and 24-hr (86 ± 3% vs 81 ± 4%). There was no difference in time to complete 2-miles between AZ and PL after 2-hr (20.7 ± 3.2 vs. 22.7 ± 5.0 min, P > 0.05) or 24-hr (21.5 ± 3.4 vs. 21.1 ± 2.9 min, P > 0.05) of exposure to altitude. Our results suggest that AZ (500 mg/day) does not negatively impact endurance exercise performance at 3500 m.