Effects of Dietary Nitrate and Caffeine on End Power and Work Above End Power During a 3 min All-Out Test in Trained Male Cyclists.

Abstract

Background: The purpose of this study was to examine the effects of acute dietary nitrate (NO₃^-) and caffeine (CAF) supplementation on end power (EP) and work performed above EP (WEP) in trained male cyclists during a 3 min all-out test (3MT) on a cycle ergometer.Methods: Fifteen healthy, trained male cyclists (28.5 ± 5.3 years, 79.2 ± 9.1 kg, VO₂peak 55.2 ± 5.6 mL·kg^-1·min^-1) completed four exercise trials in a randomized, double-blind, placebo-controlled, crossover study design separated by 3-7 days. The four experimental conditions were placebo beverage (nitrate-depleted) + placebo capsule, nitrate-rich beetroot juice + placebo capsule (BR), placebo beverage + caffeine capsule (CAF), and nitrate-rich beetroot juice + caffeine capsule (BR + CAF). Participants consumed nitrate-rich beetroot juice (~13 mmol NO₃^-) or nitrate-depleted placebo three hours before exercise, and caffeine (5 mg∙kg^-1) or maltodextrin placebo one hour before testing. EP and WEP were determined from the 3MT. Secondary outcomes included peak and mean power output. Data were analyzed using a repeated-measures ANOVA with repeated measures on condition. A p-value of 0.05 was used to determine statistical significance. Effect size was evaluated using partial eta squared.Results: No significant effect of condition was observed for EP (p = 0.401, ηp² = 0.056), WEP (p = 0.580, ηp² = 0.048), peak power (p = 0.642, ηp² = 0.046), mean power (p = 0.212, ηp² = 0.108), or total work (p = 0.217, ηp² = 0.107).Conclusions: No statistically significant differences between conditions were detected under the conditions of the present study.