Terry Graedon September 15, 2016 

Eating spinach or other greens and doing sprint interval training at high altitude seems to make muscles much stronger–like Popeye’s.

Maybe the cartoon character Popeye who swallowed spinach before flexing his muscles had a good idea. Watch for spinach, kale and beet greens that supply nitrate in the diet to star on sports training tables soon.

Spinach and Beet Greens as a Source of Nitrate:

Belgian researchers found that nitrate intake together with sprint interval training at high altitude might boost athletic performance. The research compared high-intensity, short training sessions at either regular or low oxygen levels.

Those training at normal oxygen levels took a placebo pill in addition to their training. Those training in low oxygen conditions got either placebo or nitrate supplementation. All the athletes were randomly assigned to their training group.

What Does Nitrate Do for Muscles?

After five weeks, training in low-oxygen conditions with the addition of supplemental nitrate altered muscle fiber composition. A greater proportion of muscle fibers were able to use oxygen to produce energy very quickly.

The researchers were looking specifically at muscle, not at speed or strength. It seems possible that the combination of nutritional support and training strategy might improve performance and give elite athletes an edge, though more research will be needed to confirm this effect.

Frontiers in Physiology, June 14, 2016 

What About Beets?

Previous research has shown that men who consume beet juice before exercising have better endurance. Presumably, this effect is also due to the nitrate in the beet juice. The researchers used a nitrate-depleted beet juice as a control.

In the body, nitrate from foods like green leafy vegetables is converted into nitric oxide. This relaxes blood vessels, lowering blood pressure and improving blood flow. Another dietary source of nitric oxide is dark chocolate.