Abstract
Dietary nitrate (NO3-) supplementation via beetroot juice (BJ) has emerged as a popular ergogenic aid, yet its efficacy in trained female athletes—particularly within highly demanding sports like rowing—remains underrepresented in scientific literature. This double-blind, placebo-controlled, randomized crossover study investigated the effects of acute BJ supplementation on cardiorespiratory fitness and muscle oxygenation kinetics in trained female rowers. Fourteen competitive female rowers (age: 21.4 ± 2.3 years; VO2max: 51.2 ± 3.6 mL/kg/min) completed two progressive incremental tests to exhaustion on a rowing ergometer 2.5 hours after consuming either 140 mL of nitrate-rich BJ (containing approximately 12.8 mmol NO3-) or an equal volume of nitrate-depleted placebo (PLA). Cardiorespiratory parameters were measured continuously via breath-by-breath gas analysis, while near-infrared spectroscopy (NIRS) assessed muscle oxygenation kinetics (tissue saturation index [TSI] and deoxyhemoglobin [HHb] amplitude) of the vastus lateralis. Acute BJ supplementation significantly elevated plasma nitrate concentrations compared to PLA (p < 0.001). However, no significant differences were observed between BJ and PLA in maximal oxygen uptake (VO2max), oxygen consumption at ventilatory thresholds, or time to exhaustion (p > 0.05). Interestingly, BJ supplementation attenuated the drop in TSI during the submaximal phases of the incremental test and accelerated HHb recovery kinetics post-exercise (p < 0.05). These results suggest that while acute BJ supplementation does not directly translate to immediate cardiorespiratory ergogenic benefits during incremental rowing in highly trained females, it significantly modulates local muscle oxygenation and microvascular perfusion kinetics, hinting at potential recovery-related benefits.
