The Effect of Nitrate Supplementation on Cycling Performance in the Heat in Well-Trained Cyclists

Abstract

Purpose: To determine the effect of consumption on measures of perception, thermoregulation, and cycling performance in hot conditions. Methods: In a randomized, double-blind, crossover design, 8 well-trained cyclists (mean ± SD age 25 ± 8 y, peak 64 ± 5 mL · kg−1 · min−1) performed 2 separate trials in hot (35°C, 60% relative humidity) environments, having ingested either 140 mL -rich beetroot juice ∼8 mmol (NIT) or placebo (PLA) daily for 3 d with a 7-d washout period separating trials. Trials consisted of 2 × 10-min bouts at 40% and 60% peak power output (PPO) to determine physiological and perceptual responses to the heat, followed by a 4-km cycling time trial. Results: Basal [nitrite] was substantially elevated in NIT (2.70 ± 0.98 µM) vs PLA (1.10 ± 0.61 µM), resulting in a most likely (ES = 1.58 ± 0.93) increase after 3 d. There was a very likely trivial increase in rectal temperature in NIT at 40% (PLA 37.4°C ± 0.2°C vs NIT 37.5°C ± 0.3°C, 0.1°C ± 0.2°C) and 60% (PLA 37.8°C ± 0.2°C vs NIT 37.9°C ± 0.3°C, 0.1°C ± 0.2°C) PPO. Cycling performance was similar between trials (PLA 336 ± 45 W vs NIT 337 ± 50 W, CV ± 95%CL; 0.2% ± 2.5%). Outcomes for heart rate and perceptual measures were unclear across the majority of time points. Conclusions: Three days of supplementation resulted in small increases in rectal temperature during low- to moderate-intensity exercise, but this did not appear to influence 4-km cycling time-trial performance in hot climates.