MUSCLE FORCE PRODUCTION

The Effect of Beetroot Juice (Nitric Oxide) on Muscle Force Production

The Effect of Beetroot Juice (Nitric Oxide) on Muscle Force Production

Introduction

Most studies evaluating the performance effects of beetroot juice have used time-to-exhaustion protocols, which test exercise capacity, not athletic performance, and have been criticized as having limited validity in the athletic setting. A superior test of the effectiveness of beetroot juice as an ergogenic aid would involve subjects covering a certain distance in the fastest time possible—a time trial (Lansley & Winyard et al, 2011: 591).

Lansley and colleagues9 evaluated the effect of beetroot juice consumption on power output, oxygen uptake, and performance during 4-km and 16.1-km cycling time trials. The subjects' normal dietary nitrate intake wasn't restricted at any time during the study. The competitive male cyclists consumed 0.5 L of Beet It (6.2 mmol of nitrate) or a nitrate-depleted beetroot juice placebo (0.0047 mmol of nitrate) and rested for 2 3/4 hours before completing either a 4- or 16.1-km bicycle time trial (Lansley & Winyard et al. 2011: 1125).

Background of the Research

Study leader Professor Andy Jones, from the University of Exeter's School of Sport and Health Sciences, said: ''While our previous research demonstrated the benefits of nitrate-rich beetroot juice on stamina, our latest work indicates that this is consequent to a reduced energy cost of muscle force production.

''Since our first study came out we have seen growing interest in the benefits of drinking beetroot juice in the world of professional sport and I expect this study to attract even more attention from athletes.'' The scientists believe nitrate from beetroot juice leads to increased levels of nitric oxide in the body, which affects a range of biological functions including blood flow, hormone levels and cell signaling (Lundberg & Larsen, 2011: 616).

The new findings are published in the Journal of Applied Physiology.

Prof Jones' team studied seven healthy men who were asked to complete a series of knee extension exercises while measuring their exertion levels. At the same time, a magnetic resonance imaging (MRI) scanner monitored what was going on in the volunteers' muscles.

The test was repeated several times, both after participants had drunk beetroot juice and after they had drunk blackcurrant cordial. Drinking beetroot, but not blackcurrant, was found to increase blood nitrate levels and reduce muscle usage of adenosine triphosphate, the body's chief energy source. Oxygen uptake by muscles was also lowered.

Several studies have shown that nitrate supplementation reduces the oxygen cost for a given exercise intensity 13-18. This has practical implications because exercise economy affects tolerance to high-intensity exercise 19. Three recent studies confirm that nitrate supplementation increases tolerance to high-intensity exercise by enhancing muscle contractile efficiency and reducing muscle metabolic perturbations 13, 16, 17. Mechanistically, a central target for the effects of nitrate and its metabolites seems to be the mitochondrion (Allen, 2011: 618).

In one study, healthy men were given 500 ml of a nitrate-rich beetroot juice providing 316 mg of nitrate, or placebo, 6 consecutive days. On the last 3 days they subjects completed low-intensity and ...