A 21% drop in arginine levels is observed among endurance athletes after an intense run (1). For power athletes, a 90-minute workout reduces concentrations of arginine by 15% (2). In the same subjects, five weeks of intense strength training incurred a 19% reduction in arginine levels (3).
One of the reasons that exercise uses arginine is because it forces the body to produce more NO (see below), which automatically wastes arginine and forces the body to draw on its already low reserves (4-5). On the other hand, physical activity increases the activity of the enzyme arginase, which has several anti-arginine and anti-NO effects (6).
Arginase is responsible for destroying arginine, which prevents the arginine that we absorb (in the form of food or supplements) from reaching the bloodstream. It also blocks the transformation of arginine into NO due to its vascular activity. In doing so, the production of nitric oxide is weakened due to a lack of raw material. The combination of these negative phenomena explains why over-training is associated with a drop in blood arginine levels. In turn, a depletion in NO production is noted in athletes during periods of intense training (7).
This is why when you over-train, congestion becomes less and less effective.
Even in the case of an arginine deficiency due to too little consumption, the body is unable to accelerate its own synthesis speed to compensate for increasing needs. Whey provides little arginine. Casein is a little richer in arginine, but not much. Arginine is not very present in food either. Supplementation is therefore recommended for athletes (8).
Effects of arginine
The positive effect of arginine has long been attributed solely to its ability to increase the secretion of growth hormone (GH), a hormone that promotes muscle gain and fat loss (9).
Growth hormone secretion is regulated by two hormones: GH-RH (for GH-Releasing hormone), which stimulates the secretion of GH, and somatostatin, which inhibits the secretion of GH. Arginine lowers the level of somatostatin, thereby increasing the secretion of GH (10). Today, three other mechanisms are added to the increase in GH levels to explain the benefits of arginine supplementation for athletes:
- Increasing nitric oxide (NO) levels
- Increased creatine synthesis
- The elimination of metabolic wastes that are vehicles for fatigue
Increased nitric oxide synthesis
NO is the acronym used for nitric oxide. Although it isn't a hormone, it's a gas that behaves very similarly to one. NO is produced and destroyed locally in seconds by the cells that require it. The scientific name for this family of molecules is gasotransmitters.
NO promotes muscular anabolism via both its direct and indirect effects on muscle cells, by promoting the proliferation of satellite cells (stem cells of new muscle fibres; 11-12-13-14-15-16-17-18-19). As a direct precursor of nitric oxide, arginine is the main natural booster of NO secretion. Arginine supplementation helps optimise anabolism without the need for testosterone, which is difficult to increase. On the contrary, NO production is relatively easy to increase. It has long been demonstrated that oral consumption of L-arginine causes an increase in cellular NO production (20).
The best known effect of NO is that it relaxes the smooth muscles that surround the arteries and blood vessels. This relaxation facilitates circulation in the muscles, which facilitates oxygenation and congestion. It is via this same mechanism that NO promotes male as well as female erection (of the clitoris). Carnitine can be coupled with arginine to produce even more NO to better oxygenate and nourish the muscles (21).
Increased creatine synthesis
As a precursor to creatine, arginine increases the capacity for natural creatine synthesis, which in turn increases strength, muscle mass, and recovery. In order to optimise muscle creatine increase, we advise teaming arginine with glycine, which is the second natural creatine precursor. With L-Arginine base + glycine, you can reap all the benefits of creatine without having to take creatine directly (22-23). On the other hand, because of this same precursor mechanism, athletes' arginine needs are all the more important as creatine is not used (24).
Recycling metabolic waste
Arginine also acts as an anti-fatigue agent by accelerating the evacuation of metabolic waste, such as ammonia, an excess of which is produced during exercise (8-25-26). Once in the bloodstream, ammonia can easily reach the brain, where it exacerbates the feeling of exhaustion. It is during the use of ATP as energy that the catabolism of this molecule leads to ammonia production. Instead, arginine recycles metabolic waste products to synthesise ATP instead of forming ammonia. Arginine halves the increase in ammonia during exercise. Thus, taking arginine results in an increase in endurance, as well as in strength endurance (27-28-29-30).