Acute beetroot juice supplementation does not attenuate knee extensor exercise muscle fatigue in a healthy young population

Abstract

PURPOSE: The effect of acute nitrate supplementation on muscle fatigue is largely unknown. This study aimed to evaluate the effect of acute nitrate supplementation on muscle fatigue. METHODS: Thirty-five recreationally active subjects consumed 140 ml of beetroot (BR) juice (nitrate: 8 mmol·d-1) or placebo (PL) 12 and 2.5 hours before two exercise sessions. Peak torque was measured during 50 repetitions, at maximal effort, and during concentric knee extensions at 90°·s-1. Blood pressure (BP) was recorded pre- and post-exercise. RESULTS: Peak torque, maximum work, rate of fatigue, and rate of work fatigue were similar between the BR and PL conditions. Post-exercise diastolic BP (BR: 67.2 ± 9.8 vs. PL: 64.5 ± 7.9 mmHg, p < 0.05) and mean arterial pressure (BR: 91.6 ± 9.3 vs. PL: 88.8 ± 8.2 mmHg, p < 0.05) were higher with BR supplementation. CONCLUSION: These findings suggest that the acute intake of BR juice had no effect on knee extensor muscle strength or fatigue but increased BP in a healthy recreationally active population.