Dietary Nitrate Increases Maximal Knee Extensor Speed And Power In Healthy Men And Women

Nitric oxide (NO) has been demonstrated to enhance the maximal shortening velocity and maximal power of rodent muscle. Dietary nitrate (NO 3 ‐ ) intake has been demonstrated to increase NO bioavailability in humans. We therefore hypothesized that acute dietary NO 3 ‐ intake (in the form of a concentrated beetroot juice (BRJ) supplement) would improve muscle speed and power in humans. To test this hypothesis, healthy men and women (n=8; age=34±9 y) were studied using a randomized, double‐blind, placebo‐controlled crossover design. After an overnight fast, subjects ingested 140 mL of BRJ either containing or devoid of 11.2 mmol of NO 3 ‐ . After 2 h, knee extensor speed and power were assessed using a Biodex 4 isokinetic dynamometer. Breath NO levels were also measured periodically using a Niox Mino analyzer as a biomarker of whole‐body NO production. No significant changes in breath NO were observed in the placebo trial, whereas breath NO rose by 66±25% (P<0.05) after dietary NO 3 ‐ intake. This was accompanied by a 5±2% (P<0.05) increase in muscle torque (force) production at the highest angular velocity tested (i.e., 6.28 rad/s). Calculated maximal knee extensor power therefore tended to be greater (i.e., 7.81±0.84 vs. 7.36±0.74 W/kg; P=0.08) and occurred at a higher angular velocity (i.e., 7.00±0.36 vs. 6.31±0.26 rad/s; P<0.05) after dietary NO 3 intake. We conclude that acute dietary NO 3 ‐ intake increases whole‐body NO production and muscle speed and power in healthy men and women. This improvement in muscle function may be of relevance in both athletic and clinical populations. Grant Funding Source : Supported by Washington University Mentors in Medicine, Barnes‐Jewish Hospital Foundation, and ICTS UL1 TR000448