What This Means
This research suggests that taking beetroot juice (a source of dietary nitrate) and/or caffeine before a high-intensity cycling test does not meaningfully improve key markers of cycling performance in trained male cyclists. Fifteen trained cyclists completed four separate exercise sessions under different supplement conditions — a placebo, beetroot juice alone, caffeine alone, and both combined — before performing a 3-minute maximal cycling effort. The main measures of interest were 'end power' (a proxy for critical power, or the highest sustainable exercise intensity) and the total extra work done above that threshold, but none of these outcomes differed significantly between conditions.
The study used a rigorous double-blind, placebo-controlled, crossover design, meaning neither the participants nor the researchers knew which supplement was being taken during each trial, and every participant experienced all four conditions. Beetroot juice provided roughly 13 mmol of nitrate, and caffeine was dosed at 5 mg per kilogram of body weight — doses consistent with those used in previous research showing benefits in other populations or exercise protocols. Despite this, no statistically significant effects were found for any measured outcome, including peak power, mean power, or total work.
This research suggests that the ergogenic (performance-enhancing) effects of dietary nitrate and caffeine, either alone or combined, may not extend to this specific type of short, maximal cycling effort in already-trained individuals. The relatively small sample size (15 participants) means the study may not have had enough statistical power to detect small but real effects, and the trained status of participants may have contributed to a ceiling effect where performance improvements are harder to achieve. These findings add nuance to the broader literature and highlight that supplement responses can vary depending on exercise modality, duration, and athlete training status.