The effect of beetroot juice dosage on high intensity intermittent cycling performance

Background: Resynthesis of creatine phosphate (PCr) and intramuscular pH, which influences glycolytic rate, are dependent on skeletal muscle blood flow (Sahlin et al., 1979: Scandinavian Journal of Clinical and Laboratory Investigation 39(6):551-8; Sutton et al., 1981: Clinical Science 61(3):331-8). Skeletal muscle blood flow during exercise has been shown to be enhanced following supplementation with nitrate-rich beetroot juice (BJ) through a nitrate-nitrite-nitric oxide-mediated mechanism (Ferguson et al., 2013: Journal of Physiology 591(Pt 2):547-57). Purpose: The purpose of this study was to determine if acute supplementation with BJ enhanced subsequent high intensity intermittent cycling performance and to investigate if performance gains could be influenced by varying BJ dosage. Methods: In a randomised control trial with a repeated-measures crossover design, 2 hours after consumption of low dose (250ml), high dose (500ml) of a commercially available BJ or nothing, 8 active young males (24 ± 8.5yrs) completed three 30s Wingate anaerobic tests (WAnT) on a Monark 894E interspersed with 3 minutes active cycling recovery at low intensity. The three trials were separated by a 7-day washout period for each participant. Peak power (PP), mean power (MP) and fatigue index (FI) were recorded for each WAnT and were compared using a two-way repeated measures ANOVA. Results: MP declined successively in the second and third WAnT in each trial (p