To many bodybuilders and athletes, Cortisol is a dirty word. Perhaps no other hormone, with the exception of estrogen, provokes such fear in those who are interested in gaining muscle mass and increasing athletic prowess. The fact that similarly to both testosterone and estrogen, cortisol is a steroid hormone often causes confusion since it's often referred to as a "steroid" in newspapers and magazines. The word "steroid" simply refers to substances that are produced from a cholesterol precursor or raw material. The cholesterol, which travels in the blood attached to a protein called low-density lipoprotein (LDL), undergoes a series of enzymatic transformations to become particular steroid hormones. The fear that cortisol arouses is based on its effects as the most potent catabolic hormone in the body. The word "catabolic" refers to something that breaks down something else. In this case, elevated cortisol levels can indeed promote the breakdown of muscle under certain circumstances. Although when it comes to the promotion of muscular growth the emphasis is often placed on "anabolic" reactions, which is the opposite of catabolic effects, people often overlook the fact that muscle growth is the result of a balance between anabolic and catabolic effects. An anabolic effect in muscle would involve increased muscle protein synthesis (MPS). This increased MPS is promoted by exercise and the ingestion of essential amino acids, particularly the branched-chain amino acids, with leucine being the most potent in this regard. Your muscles grow when the rate of MPS exceeds that of muscle breakdown. Or to put it another way, muscular growth is the result of a dominance of anabolic effects over catabolic effects. At rest, catabolic effects dominate, but with the impetus of exercise and nutrition, anabolic effects such as increased MPS dominate. But the point is that both processes, anabolic and catabolic, are constantly occurring.
What is overlooked is that if you seek muscular gains, you not only want to potentiate anabolic effects in muscle, but you also want to blunt catabolic effects, too. Just lowering catabolic effects in muscle will tip the balance towards anabolism in muscle, which will again result in muscle gains. For example, most people are aware that anabolic steroid drugs help to build muscle mass. This is hardly a secret. The usual way that steroids, which are synthetically restructured forms of testosterone, an anabolic hormone, work is by a greatly enhanced promotion of muscle protein synthesis. Interestingly, recent studies show that steroids do this by promoting the activity of an enzyme, mTOR, that is pivotal in the MPS process. Certain amino acids, such as leucine, do the same thing. The reason why steroids are so much more potent in this effect is that steroids provide a more sustained effect compared to amino acids. Amino acids increase MPS for only a relatively short time, about 2 1/2 hours after ingestion. Following that, a muscle becomes refractory to amino acid stimulation . . .