Effects of Acute Beetroot Juice on Aerobic Performance and Muscle Oxygenation in Amateur Female Soccer Players

This randomized, double-blind, placebo-controlled crossover study evaluated the acute effects of nitrate-rich beetroot juice supplementation on aerobic performance, muscle oxygenation, and selected physiological responses in amateur female soccer players.

Thirteen participants completed two experimental conditions in randomized order, separated by a 7-day washout period. In one condition, participants consumed 70 mL of nitrate-rich beetroot juice containing 6.4 mmol of nitrate, while in the other condition they consumed an equal volume of low-nitrate blackcurrant placebo containing <0.1 mmol of nitrate. Each beverage was consumed 2.5 hours before exercise testing.

Aerobic performance was assessed using a treadmill-adapted 12-minute Cooper test. Total distance covered and estimated maximal oxygen uptake (VO₂max) were evaluated as performance outcomes. Muscle oxygen saturation was monitored using near-infrared spectroscopy. Heart rate, blood pressure, blood glucose, and rating of perceived exertion were also assessed at predefined time points. Participants and investigators conducting the experimental procedures were blinded to the supplementation condition, and the supplementation sequence was generated by an independent researcher who was not involved in the experimental procedures or statistical analyses.

Inclusion criteria

• Female
• Aged 18 years or older
• Licensed soccer player for at least 3 years

Exclusion criteria

• Use of pharmacological treatment or supplements/ergogenic aids that could affect exercise performance, including stimulants such as caffeine
• Presence of musculoskeletal, ligament, bone, neurological, or joint pathology incompatible with the exercise protocol
• Current cardiovascular problems
• Participation in additional sports or physical activities during the study period that could affect the study outcomes