The impact of beetroot juice supplementation on muscular endurance, maximal strength and countermovement jump performance

Abstract

Purpose: Dietary nitrate has been shown to enhance muscle contractile function and has, therefore, been linked to increased muscle power and sprint exercise performance. However, the impact of dietary nitrate supplementation on maximal strength, performance and muscular endurance remains to be established. Methods: Fifteen recreationally active males (25 ± 4 y, BMI 24 ± 3 kg/m²) participated in a randomized double-blinded cross-over study comprising two 6-d supplementation periods; 140 mL/d nitrate-rich (BR; 985 mg/d) and nitrate-depleted (PLA; 0.37 mg/d) beetroot juice. Three hours following the last supplement, we assessed countermovement jump (CMJ) performance, maximal strength and power of the upper leg by voluntary isometric (30° and 60° angle) and isokinetic contractions (60, 120, 180 and 300°·s⁻¹), and muscular endurance (total workload) by 30 reciprocal isokinetic voluntary contractions at 180°·s⁻¹. Results: Despite differences in plasma nitrate (BR: 879 ± 239 vs. PLA: 33 ± 13 μmol/L, P < 0.001) and nitrite (BR: 463 ± 217 vs. PLA: 176 ± 50 nmol/L, P < 0.001) concentrations prior to exercise testing, CMJ height (BR: 39.3 ± 6.3 vs. PLA: 39.6 ± 6.3 cm; P = 0.39) and muscular endurance (BR: 3.93 ± 0.69 vs. PLA: 3.90 ± 0.66 kJ; P = 0.74) were not different between treatments. In line, isometric strength (P > 0.50 for both angles) and isokinetic knee extension power (P > 0.33 for all velocities) did not differ between treatments. Isokinetic knee flexion power was significantly higher following BR compared with PLA ingestion at 60°·s⁻¹ (P = 0.001), but not at 120°·s⁻¹ (P = 0.24), 180°·s⁻¹ (P = 0.066), and 300°·s⁻¹ (P = 0.36). Conclusion: Nitrate supplementation does not improve maximal strength, countermovement jump performance and muscular endurance in healthy, active males.

Keywords:

• Exercise
• fitness
• musculoskeletal
• nutrition

Acknowledgements

We thank Joan M.G. Senden (Maastricht University) for the analysis of plasma nitrate and nitrite concentrations. This study was designed by KLJ, LBV, LJCvL and JWvD; data were collected by DH, HP and JWvD and analysed by KLJ, DH, HBP and MdN; data interpretation and manuscript preparation were undertaken by KLJ, DH, LBV, LJCvL and JWvD. All authors approved the final version of the paper.

Disclosure statement

Over the last 5 years, LBV, LJCvL and JWvD have received research grants, consulting fees, and/or speaking honoraria from Friesland Campina, and LBV and LJCvL have received research grants, consulting fees, and speaking honoraria from Pepsico.

Additional information

Funding

This study was part of the EAT2MOVE project and supported by a grant from the Province of Gelderland.