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.

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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.

IGF-1
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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.

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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.

Abstract

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]

Source: http://www.ncbi.nlm.nih.gov/pubmed/18708688 

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