A study finds that a popular nutritional supplement marketed to lead to greater muscle strength does not increase blood flow as it claims.

Various nutritional supplements have been developed containing arginine-alpha-ketoglutarate (AAKG) a salt of the amino acid arginine and alpha-ketoglutaric acid, which promises increase nitric oxide production thereby resulting in increased "vasodilation" widening of blood vessels, increasing blood flow to the muscles.

The supplement market promote AAKG supplement-enhanced blood flow to working muscles during resistance exercise is alleged to provide increased muscle strength than just exercise alone.

Researchers at Baylor studied the effects of AAKG in 24 men using the supplement for seven days, on atrial blood flow into the arms after a single bout of resistance exercise. The results showed AAKG supplementation had no significance impact on blood movement or increased brachial artery blood flow in response to single bout of resistance exercise.

The study appears in the August edition of the International Journal of Sport Nutrition and Exercise Metabolism.

"We did see a slight increase in blood flow but those effects can only be attributed to the resistance exercise and not to the supplement," said study author Dr. Darryn Willoughby, associate professor of exercise, nutritional biochemistry and molecular physiology at Baylor.

"The data appear to refute the alleged supposition and manufacturer's claims that 'vasodilating supplements' are effective at causing vasodilation, thereby resulting in increased blood flow to active skeletal muscle during resistance exercise." said Willoughby