Likely Additive Ergogenic Effects of Combined Preexercise Dietary Nitrate and Caffeine Ingestion in Trained Cyclists

Aims. To evaluate the possible additive effects of beetroot juice plus caffeine on exercise performance. Methods. In a randomized, double-blinded study design, fourteen healthy well-trained men aged years performed four trials on different occasions following preexercise ingestion of placebo (PLA), PLA plus 5？mg/kg caffeine (PLA+C), beetroot juice providing 8？mmol of nitrate (BR), and beetroot juice plus caffeine (BR+C). Participants cycled at 60% maximal oxygen uptake ( max) for 30？min followed by a time to exhaustion (TTE) trial at 80% max. Saliva was collected before supplement ingestion, before exercise, and after the TTE trial for salivary nitrate, nitrite, and cortisol analysis. Results. In beetroot trials, saliva nitrate and nitrite increased >10-fold before exercise compared with preingestion ( ). TTE in BR+C was 46% higher than in PLA ( ) and 18% and 27% nonsignificant TTE improvements were observed on BR+C compared with BR and PLA+C alone, respectively. Lower ratings of perceived exertion during TTE were found during 80% max on BR+C compared with PLA and PLA+C ( for both). Conclusions. Acute preexercise beetroot juice coingestion with caffeine likely has additive effects on exercise performance compared with either beetroot or caffeine alone. 1. Introduction Dietary supplement intake, in addition to training, appropriate nutrition, and advantageous gene polymorphisms, is recognized to confer exercise performance benefits [1–4]. Such supplements (e.g., caffeine, bicarbonate, creatine, and beta alanine) are widely consumed by athletes in many sports. The role of caffeine as an ergogenic aid is well established. The study by Costill et al. [5] was the first to demonstrate improved time-to-exhaustion (TTE) exercise with acute preexercise ingestion of caffeine. Subsequent investigations reported that caffeine intake can improve cycling [6, 7], high intensity running [8, 9], and repeated sprint running performance [10]. A recent review on the effects of caffeine on exercise performance suggested that, at least in endurance sports, even small to moderate caffeine doses (2-3？mg/kg of body mass) are likely to confer performance benefits [11]. Caffeine induces numerous physiological effects. Although its stimulating effects on exercise performance in humans were initially thought to occur via increased fatty acid oxidation rates and muscle glycogen-sparing effect [5, 7], several studies reported conflicting findings [12, 13]. In addition to peripheral actions, caffeine was shown to reduce perception of effort during exercise, suggesting that some