Beetroot Beverage and Repeated Sprint Power Output During RAST

This randomized, double-blind, placebo-controlled crossover trial is designed to investigate the acute effects of a nitrate-rich beetroot-based beverage on repeated sprint performance in trained athletes. Ten athletes will participate in two experimental sessions in randomized order: beetroot beverage (BET) and placebo (PLA). Randomization will determine the sequence of beverage administration. Participants and investigators will be blinded to treatment allocation. After beverage ingestion, participants will perform a standardized warm-up followed by the Running Anaerobic Sprint Test (RAST), consisting of six maximal 35-meter sprints with 10 seconds of passive recovery between sprints. Sprint time will be recorded using electronic timing, and power output will be calculated using body mass and sprint time. The primary outcome measure is mean power output across all six sprints. Secondary outcomes include: Fatigue index (percentage decrement across sprints) Individual sprint power (S1-S6) Heart rate response Rating of perceived exertion (Borg 6-20 scale) VO₂max (assessed at baseline) Sleep quality measured using the Insomnia Severity Index (ISI) A linear mixed-effects model will be used to analyze repeated sprint performance, including subject as a random intercept and treatment, sprint, and their interaction as fixed effects. Non-parametric tests will be applied when assumptions of normality are not met. Statistical significance will be set at p ≤ 0.05.