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

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More IGF-1 in muscle tissue with creatine

Men and women weight trainers manufacture more of the anabolic hormone IGF-1 in their muscle cells. If they take creatine as well, the production of IGF-1 in the muscles is even higher. Sports scientists at the Canadian St Francis Xavier University discovered this in an experiment they did with about forty healthy people in their twenties.

Creatine & IGF-1
The researchers got their subjects to do weight training and gave half of them creatine supplements. The other half were given a placebo. After eight weeks the researchers measured the amount of IGF-1 in the muscles of the subjects. In the placebo group they recorded an increase of 54 percent. In the creatine group the increase was 78 percent.

IGF-1 has a strong anabolic effect. In athletes the type of IGF-1 that the muscle cells manufacture themselves is important, and this is influenced by training, amino acids and, as we now know, creatine. Different forms of IGF-1 are found in the body. Scientists suspect that there is a 'bad' kind of IGF-1, which increases the risk of cancer, and a 'good' IGF-1 that causes specific muscles to grow. Doping users inject a form of IGF-1, of which researchers don't know for sure whether it's the 'good' or 'bad' type.

Older study
The Canadian findings are actually not new. Four years ago a research group in Louvain, Belgium reported that creatine had increased the production of IGF-1 in muscle cells in test tube experiments. [FEBS Lett. 2004 Jan 16;557(1-3):243-7.] A year later, in 2005, the same researchers reported that they had also found an increased level of IGF-1 in the muscle tissue of human weight trainers. [Med Sci Sports Exerc. 2005 May;37(5):731-6.] The figure below comes from that publication.

The Belgians got their subjects to do weight training and gave them a daily dose of 21 g of creatine for five days. Before each training session the subjects drank a protein shake with carbohydrates.

More IGF-1 in muscle tissue with creatine

The effect is clear. Three hours after training, when your muscles start to recover and hopefully grow, the production of IGF-1 increases more if you use creatine.

The Belgians also demonstrate in their article that creatine makes other anabolic signalling molecules in muscle cells more active, such as 4E-BP1 and p70-S6K. This leads them to conclude that "creatine supplementation could act to stimulate muscle growth, but not by a rapidly responding control system as observed after exercise plus feeding, but rather by a late-response enhancement of the anabolic status of the cell involving IGF".

So you could say creatine is not only a training booster, but an anabolic agent as well.

Int J Sport Nutr Exerc Metab. 2008 Aug; 18(4):389-98.