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Definition: "An ergogenic aid is any substance or phenomenon that enhances performance "

15.06.2010

Arginine with grape extract enhances stamina

A supplement containing the amino acid L-arginine and a grape-skin extract raises the intensity at which you can train without getting suddenly exhausted to the point that you cannot physically function. Sports scientists from the University of Nebraska-Lincoln have published their findings in the Journal of Strength and Conditioning Research.

Extracts of grapeseed or grape skin contain phenols that inhibit the breakdown of the 'good' radical nitrogen monoxide [NO] in the body. Because more NO keeps blood vessel walls supple, the extracts protect the blood vessels and increase the ease with which the heart can pump oxygen and nutrients to the muscles.

L-arginine is a precursor of NO. That the combination of L-arginine and grape extract enhances condition is not such a strange idea. Physical exertion causes more ammonia to be released into the blood, and that causes fatigue. L-arginine speeds up the processes in the body that remove ammonia.

Studies on whether L-arginine reduces tiredness are inconclusive, and this is the first time that a combination of grape extract and L-arginine has been studied. That's why the supplements manufacturer General Nutrition Corporation financed this study in which 1500 mg L-arginine was combined with 150 mg grape skin extract.

The 50 male test subjects [average age: 23] took the supplement for 4 weeks. Some of the group were given a placebo, others took a daily 1500 mg L-arginine and 150 mg grape extract, and yet another group took double this dose. The subjects did not do regular exercise.

Before and after the 4-week period, the researchers determined the physical working capacity at the fatigue threshold [PWCFT] of their subjects when they cycled. The graph below shows what this is. The figure shows the data for one person.

The highest intensity at which the fatigue of the subject does not increase significantly is 140 Watt. When the intensity reaches 170 Watt, exhaustion suddenly sets in. You calculate the PWCFT by taking the average of these figures. In other words: the level of intensity at which you can exercise for a long period without getting exhausted. In this case that's at 155 Watt.

The PWCFT rose in the subjects who took supplements. You don't even need that much L-arginine to achieve this – the light dosage works just as well as the heavy dose.

"These findings supported the use of arginine-based supplements, at the dosages examined in the present investigation, as an ergogenic aid for untrained individuals", the researchers conclude.

Source:
J Strength Cond Res. 2010 May; 24(5): 1306-12.

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