Effects of caffeine and acute exercise on the validity of a submaximal cycle ergometer test: a randomised, placebo-controlled crossover study.

Abstract

Purpose: To investigate the effects of caffeine (Caf) consumption and prior exercise on the validity of the Ekblom-Bak cycle test (EB-test) for estimating maximal oxygen uptake (VO₂max).Methods: Healthy, habitual caffeine users received 250 mg Caf or placebo (Pla) in a double-blind randomised crossover design separated by one week. Each visit included two EB-tests performed before and after a maximal treadmill exercise (Ex). Heart rate (HR), blood pressure (BP), and oxygen uptake were measured, and estimation error was calculated as estimated-measured VO₂max. Data were analysed using repeated measures ANOVA with condition (Caf, Pla) and time (pre-Ex, post-Ex) as within-subject factors.Results: Participants were 15 women and 17 men (33.5 ± 11.1 years). Resting HR and BP did not differ between trials, except for a modest increase in systolic BP after Caf (129 ± 14 mmHg vs. 122 ± 15 mmHg; p = 0.042). Maximal HR and VO₂max were unaffected, but time to exhaustion increased with caffeine (438 ± 73 s vs. 415 ± 69 s; p = 0.012). HR increased significantly from pre- to post-Ex, with no differences between Caf and Pla conditions. Estimation errors rose from pre- to post-Ex (-0.17 and - 0.12 L·min⁻¹ to - 0.28 and - 0.30 L·min⁻¹), independent of caffeine intake, body mass, or measured VO₂max.Conclusion: Caffeine did not affect the accuracy of the VO₂max estimation from the EB-test. However, strenuous exercise before testing increased estimation errors, suggesting that recent intense exercise has a greater impact on EB-test validity than moderate caffeine consumption.