Leafy Greens for Enhancing Sports Endurance

Nitrate supplements have ignited a new conversation about nitrate-rich foods like spinach, arugula, and other vegetables, as being important for muscle endurance during exercising. A previous study has suggested that beetroot juice, an abundant dietary source of nitrate, increases blood flow to the skeletal muscles during exercise by 38%. In a recent sports performance study, it was found that athletes who took nitrate supplementation before undergoing endurance training experienced improved muscle performance.

These tests were done on stationary bicycles, and the participants were placed in a low oxygen (hypoxic) environment. Biopsies of muscle tissue were taken and the results showed a growth in muscle fibers. This would suggest that nitrate is a key nutrient for the muscles during exercise.

In Belgium at the University of Leuven, researchers recruited 30 healthy men from university students. All participants were selected for being physically active, but were not engaged in any physical training program. The participants were divided into three groups and took either a placebo, or nitrate pills three hours prior to exercising. Then, over a five-week period, participants undertook an intense exercise program on stationary bikes. Each trial would last for 30 minutes, three times per week. The groups were categorized as seen below:

• Group one took placebos and exercised in normal oxygen conditions
• Group two took placebos and exercised under low oxygen conditions
• Group three took nitrate supplements and exercised under low oxygen conditions

The researchers took muscle biopsies to measure certain fibers in the muscle tissue, specifically the ones thought to be associated with increasing endurance. In the final analysis, the group of athletes who took nitrate supplements before exercising in a low oxygen environment had a measured increase in these muscle fibers. This suggests that ingesting nitrate-rich foods or supplements combined with endurance type exercise regimes will grow those muscles needed for high-performance sports.

According to co-author Professor Peter Hespel, this may be the first study that shows changes inside muscle fibers after nitrate supplementation with exercise. The study was first considered after examining athletes who train at high elevations under conditions of low oxygen to improve their performance. Under these conditions, intense workouts put extra demands on the muscles as they quickly undergo oxidative stress due to the low oxygen.

It was believed that muscle fibers would respond to nitrate intake and boost overall performance. As the study discovered, nitrate supplements did increase muscle performance under extreme conditions, but it remains to be seen if this success can be implemented under normal oxygen conditions. Hespel also cautioned that long-term nitrate supplementation with exercise is not yet recommended, until a safe dosage of nitrate has clearly been demonstrated.

This experiment demonstrated nitrate supplementation and vigorous training under hypoxic conditions proportionally increased muscle fiber associated with endurance. Today, athletes are pushing themselves to their physical limits. Future research in dietary supplements could give them a competitive edge. However, Professor Hespel suspects further investigation into nitrate-rich foods could be a safe alternative for athletes wanting to improve their performance.