The effects of sodium bicarbonate supplementation at individual time‐to‐peak blood bicarbonate on 4‐km cycling time trial performance in the heat

Abstract

The purpose of this study was to explore the effect of individualised sodium bicarbonate (NaHCO₃) supplementation according to a pre-established individual time-to-peak (TTP) blood bicarbonate (HCO₃^-) on 4-km cycling time trial (TT) performance in the heat. Eleven recreationally trained male cyclists (age: 28 ± 6 years, height: 180 ± 6 cm, body mass: 80.5 ± 8.4 kg) volunteered for this study in a randomised, crossover, triple-blind, placebo-controlled design. An initial visit was conducted to determine TTP HCO₃^- following 0.2 g.kg^-1 body mass (BM) NaHCO₃ ingestion. Subsequently, on three separate occasions, participants completed a 4-km cycling TT in the heat (30 degrees centigrade; °C) (relative humidity ∼40%) following ingestion of either NaHCO₃ (0.2 g.kg^-1 body mass), a sodium chloride placebo (0.2 g.kg^-1 BM; PLA) at the predetermined individual TTP HCO₃^-, or no supplementation (control; CON) . Absolute peak [HCO₃^-] prior to the 4-km cycling TT's was elevated for NaHCO₃ compared to PLA (+2.8 mmol.l^-1; <i>p</i> = 0.002; <i>g</i> = 2.2) and CON (+2.5 mmol.l^-1; <i>p</i> < 0.001; <i>g</i> = 2.1). Completion time following NaHCO₃ was 5.6 ± 3.2 s faster than PLA (1.6%; CI: 2.8, 8.3; <i>p</i> = 0.001; <i>g</i> = 0.2) and 4.7 ± 2.8 s faster than CON (1.3%; CI: 2.3, 7.1; <i>p</i> = 0.001; <i>g</i> = 0.2). These results demonstrate that NaHCO₃ ingestion at a pre-established individual TTP HCO₃^- improves 4-km cycling TT performance in the heat, likely through enhancing buffering capacity.<b>Highlights</b> This is the first time NaHCO₃ ingestion has been shown to improve 4-km cycling TT performance in conditions of high ambient heat.A smaller dose of NaHCO₃ (0.2 g.kg^-1 BM) is ergogenic in the heat, which is smaller than the dose typically ingested for sports performance (0.3 g.kg^-1 BM). This is important, as gastrointestinal discomfort is typically lower as the dose reduces.This study suggests that the individualised time-to-peak HCO₃^- ingestion strategy with lower doses of NaHCO₃ is an ergogenic strategy in conditions of high ambient heat.