Caffeine appears to have a stimulating effect on the central nervous system and as such, is commonly used by athletes to improve performance(1). Nitrate-rich beetroot juice is also used as an ergogenic aid, demonstrating positive effects on both cycling economy and time-trial performance(2). While previous research has shown no additional benefits of combining caffeine and beetroot juice on cycling performance(3), no studies have compared the effects of individual and combined supplementation during running exercise. Therefore, the aim of the current study was to investigate the effects of caffeine and beetroot-juice supplementation during sub-maximal and maximal running.
Nine recreational runners (seven males, VO2max 59.0 ± 2.9 l/min; two females, VO2max 53.1 ± 11.4 l/min) performed four laboratory-based test sessions in a crossover-design study. Each test session consisted of two, 5-minute sub-maximal running bouts at ~ 70% and 80% of VO2max followed by a maximal 1-km time trial (TT). The participants were given a 70-ml dose of concentrated beetroot juice containing either 4 mmol of nitrate (BJ) or no nitrate (placebo, P) 2.5 hours before warming up for each test. Participants were also given either 4-6 mg/kg body weight of caffeine (C) or a non-caffeine-containing placebo (P) 45 minutes before warming up. The four trials (BJ+C, BJ, C and P) were double-blinded and presented in a randomised order. Data were analysed using one-way ANOVAs with repeated measures.
There were no significant differences between the four interventions for running economy, respiratory exchange ratio (RER), heart rate (HR) or rating of perceived exertion (RPE) at either of the sub-maximal running intensities (p > 0.05). Neither were there any significant differences in maximal HR or RPE, peak blood lactate concentration or 1-km TT performance between the four interventions (p > 0.05).
This study has shown no beneficial effects of combining caffeine and beetroot juice on sub-maximal or maximal running performance compared with BJ, C or P alone.
1. Burke LM (2008) Appl Physiol Nutr Metabol 33, 1319-1334.
2. Cermak NM, Gibala MJ & van Loon LJC (2012). Int J Sport Nutr Exerc Metab 22, 64-71.
3. Lane SC, Hawley JA, Desbrow B et al. (2014). Appl Physiol Nutr Metabol 39, 1050-1057.