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/m(2)) 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 degrees and 60 degrees angle) and isokinetic contractions (60, 120, 180 and 300 degrees center dot s(-1)), and muscular endurance (total workload) by 30 reciprocal isokinetic voluntary contractions at 180 degrees center dot s(-1).Results: Despite differences in plasma nitrate (BR: 879 +/- 239 vs. PLA: 33 +/- 13 mu mol/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 degrees center dot s(-1)(P = 0.001), but not at 120 degrees center dot s(-1)(P = 0.24), 180 degrees center dot s(-1)(P = 0.066), and 300 degrees center dot s(-1)(P = 0.36).Conclusion: Nitrate supplementation does not improve maximal strength, countermovement jump performance and muscular endurance in healthy, active males.
- DIETARY NITRATE SUPPLEMENTATION
- MUSCLE FORCE