Acetazolamide reduces exercise capacity following a 5-day ascent to 4559 m in a randomised study

Arthur R Bradwell; Kimberley Ashdown; Carla Rue; John Delamere; Owen D Thomas; Samuel J E Lucas; Alex D Wright; Stephen J Harris; Stephen D Myers; Birmingham Medical Research Expeditionary Society

doi:10.1136/bmjsem-2017-000302

Acetazolamide reduces exercise capacity following a 5-day ascent to 4559 m in a randomised study

BMJ Open Sport Exerc Med. 2018 Jan 23;4(1):e000302. doi: 10.1136/bmjsem-2017-000302. eCollection 2018.

Authors

Arthur R Bradwell¹, Kimberley Ashdown², Carla Rue², John Delamere¹, Owen D Thomas¹, Samuel J E Lucas³, Alex D Wright¹, Stephen J Harris⁴, Stephen D Myers²; Birmingham Medical Research Expeditionary Society

Affiliations

¹ Institute of Clinical Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK.
² Department of Sport and Exercise Sciences, University of Chichester, Chichester, UK.
³ School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK.
⁴ QinetiQ Group Plc, Farnborough, UK.

Abstract

Objective: To assess whether acetazolamide (Az), used prophylactically for acute mountain sickness (AMS), alters exercise capacity at high altitude.

Methods: Az (500 mg daily) or placebo was administered to 20 healthy adults (aged 36±20 years, range 21-77), who were paired for age, sex, AMS susceptibility and weight, in a double-blind, randomised manner. Participants ascended over 5 days to 4559 m, then exercised to exhaustion on a bicycle ergometer, while recording breath-by-breath gas measurements. Comparisons between groups and matched pairs were done via Mann-Whitney U and Pearson's χ² tests, respectively.

Results: Comparing paired individuals at altitude, those on Az had greater reductions in maximum power output (P_max) as a percentage of sea-level values (65±14.1 vs 76.6±7.4 (placebo); P=0.007), lower VO_2max (20.7±5.2 vs 24.6±5.1 mL/kg/min; P<0.01), smaller changes from rest to P_max for VO₂ (9.8±6.2 vs 13.8±4.9 mL/kg/min; P=0.04) and lower heart rate at P_max (154±25 vs 167±16, P<0.01) compared with their placebo-treated partners. Correlational analysis (Pearson's) indicated that with increasing age P_max (r=-0.83: P<0.005) and heart rate at P_max (r=-0.71, P=0.01) reduced more in those taking Az.

Conclusion: Maximum exercise performance at altitude was reduced more in subjects taking Az compared with placebo, particularly in older individuals. The age-related effect may reflect higher tissue concentrations of Az due to reduced renal excretion. Future studies should explore the effectiveness of smaller Az doses (eg, 250 mg daily or less) in older individuals to optimise the altitude-Az-exercise relationships.

Keywords: altitude; elderly people; exercise.