Influence of dietary nitrate on the physiological determinants of exercise performance: a critical review.

Dietary nitrate supplementation, usually in the form of beetroot juice, has been heralded as a possible new ergogenic aid for sport and exercise performance. Early studies in recreationally active participants indicated that nitrate ingestion significantly reduces the O2 cost of submaximal exercise and improves performance during high-intensity endurance exercise. Subsequent studies have begun to address the physiological mechanisms underpinning these observations and to investigate the human populations in whom, and the exercise conditions (high- vs. low-intensity, long- vs. short-duration, continuous vs. intermittent, normoxic vs. hypoxic) under which, nitrate supplementation may be beneficial. Moreover, the optimal nitrate loading regimen in terms of nitrate dose and duration of supplementation has been explored. Depending on these factors, nitrate supplementation has been shown to exert physiological effects that could be conducive to exercise performance enhancement, at least in recreationally active or sub-élite athletes. This article provides a "state-of-the-art" review of the literature pertinent to the evaluation of the efficacy of nitrate supplementation in altering the physiological determinants of sport and exercise performance.