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.
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.
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.
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.
Effect of creatine supplementation and resistance-exercise training on muscle insulin-like growth factor in young adults.
The purpose of this study was to compare changes in muscle insulin-like growth factor-I (IGF-I) content resulting from resistance-exercise training (RET) and creatine supplementation (CR). Male (n=24) and female (n=18) participants with minimal resistance-exercise-training experience (=1 year) who were participating in at least 30 min of structured physical activity (i.e., walking, jogging, cycling) 3-5 x/wk volunteered for the study. Participants were randomly assigned in blocks (gender) to supplement with creatine (CR: 0.25 g/kg lean-tissue mass for 7 days; 0.06 g/kg lean-tissue mass for 49 days; n=22, 12 males, 10 female) or isocaloric placebo (PL: n=20, 12 male, 8 female) and engage in a whole-body RET program for 8 wk. Eighteen participants were classified as vegetarian (lacto-ovo or vegan; CR: 5 male, 5 female; PL: 3 male, 5 female). Muscle biopsies (vastus lateralis) were taken before and after the intervention and analyzed for IGF-I using standard immunohistochemical procedures. Stained muscle cross-sections were examined microscopically and IGF-I content quantified using image-analysis software. Results showed that RET increased intramuscular IGF-I content by 67%, with greater accumulation from CR (+78%) than PL (+54%; p=.06). There were no differences in IGF-I between vegetarians and nonvegetarians. These findings indicate that creatine supplementation during resistance-exercise training increases intramuscular IGF-I concentration in healthy men and women, independent of habitual dietary routine.
PMID: 18708688 [PubMed – indexed for MEDLINE]