In exercised muscle, a great deal of attention has been focused on IGF-I through its effects on increasing protein (sarcomere) formation. An increase in IGF-I is seen in muscle after acute maximal eccentric bouts of exercise.  Local production of IGF-I undoubtedly stimulates the growth of postnatal muscle and an increase in muscle mass. mRNA for IGF-I is seen in myoblasts (i.e. satellite cells) and myotubes in vivo in injured muscle, and the pattern corresponds closely to that for satellite cell activation.  As you probably are aware, mRNA IGF-1 increases muscle hypertrophy primarily thru activating satellite cell activity. In a recent issue of the Journal of Physiology a new study was published that reported that Cr can also increase satellite cell activity.  In that study, in a double-blinded design 32 healthy, male subjects were assigned to strength training for 16 weeks while receiving either Cr, protein, or a placebo. Muscle biopsies were obtained at week 0, 4, 8 (week 8 not CON) and 16 of resistance training (3 days per week). Results of the study concluded that all training regimes were found to increase the proportion of satellite cells, but significantly greater enhancements were observed with Cr supplementation at week 4 and at week 8. Furthermore, Cr supplementation resulted in an increased number of myonuclei per fiber and increases of 14-17% in muscle fiber area at week 4, 8 and 16. In contrast, the protein drink group showed increase in muscle fiber area only in the later (16 week, +8%). This study is pretty important to bodybuilders in that it's the first study that shows Cr supplementation in combination with strength training amplifies the training-induced increase in satellite cell number and myonuclei concentration in human skeletal muscle fibers, thereby allowing an enhanced muscle fiber growth in response to strength training.  

In conclusion, Cr supplementation affords a scientifically proven means of improving performance and increasing muscle hypertrophy during exercise of high to maximal intensity. Cr supplementation has the potential to benefit all bodybuilders engaged in training that involves repetitive bouts of high-intensity exercise. The increased training load that could be tolerated by bodybuilders might be greatly beneficial to their eventual competitive performance. Additionally, Cr is probably about one of the cheapest supplements that actually improves muscle hypertrophy.    

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