No placebo or ergogenic effect of beetroot juice during virtual-reality
20-min cycling time trials: a randomised, balanced placebo design remote
study
Abstract
A large body of evidence has shown that placebo effects of dietary
supplements can improve sport performance. However, very few studies are
conducted outside of the laboratory. This is important given that
placebo effects may be more likely to be induced during highly
controlled, artificial environments in the presence of a researcher. In
the past three years, home-based, virtual-reality cycling has increased
in popularity, where over 3-million athletes train or compete against
athletes worldwide. The aim of this study was to examine placebo effects
of an acute dose of beetroot juice during 20-minute cycling virtual
reality time-trials. In line with the CONSORT statement, we used a
between-participant, randomised balanced placebo design, and recruited
67 trained cyclists who performed 3x20-min cycling time-trials
(familiarisation, baseline and experimental) on a virtual-reality
software at home. During experimental trials, participants were
randomised to one of four groups: 1) told beetroot juice/given beetroot
juice, 2) told beetroot juice/given placebo, 3) told placebo/given
beetroot juice, and 4) told placebo/given placebo, who received
nitrate-rich beetroot juice (containing ~552 mg nitrate)
or nitrate-depleted placebo (containing ~0.2 mg
nitrate). Compared to baseline, performance during experimental
time-trials was not different in any of the groups (effect size range:
0.00 to 0.14). Our results, indicate that placebo effects and beetroot
juice do not improve virtual-reality 20-min cycling time-trial
performance. These results have important considerations for future
research to determine the occurrence of placebo effects and
effectiveness of dietary supplements outside of the laboratory.