By now you must have heard thousands of times how cortisol (C) is catabolic and will break down all your hard-earned muscle. You might even be using various drugs or supplements to suppress cortisol release in the hopes that perhaps this will help you to get bigger or stronger. Now, on the surface it appears to make sense for you to want to suppress C, after all it is catabolic. There is one little catch though: Without C many important metabolic reactions become impaired. The result: Muscle weakness and in severe cases death. So, the trick is to train hard enough to stimulate muscle growth without sending your C levels through the roof. Normal, healthy ranges of C are what we want, not levels suppressed so far down that we can't even measure them.
What Is Cortisol?
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Cortisol, or hydrocortisone, is a member of a family of hormones collectively referred to as glucocorticoids. Glucocorticoids get their name from their ability to increase blood glucose levels. While there are other glucocorticoids, C is the key player in healthy individuals. Let's say you are lifting weights or stressed out from an argument. Both of these examples are types of stress. Stress can be physical, mental, or emotional. Stress stimulates your central nervous system (the brain and spinal cord). In turn, nerve cells, in a region of the brain referred to as the hypothalamus, get excited. They release a protein called corticotropin-releasing-factor or CRF. Now CRF in turn stimulates the anterior pituitary (a gland in the brain) to secrete adrenocorticotropic hormone or ACTH. ACTH then stimulates the adrenal cortex to produce C. Cortisol now goes to work by helping to raise your blood glucose levels. It travels in the body either bound to a protein or unbound in a "free" state. While different proteins can bind C, only one (corticosteroid binding globulin) prevents C from working in the body. The rest of the C in your body is active, meaning it can raise blood sugar, breakdown muscle, decrease inflammation, and control the immune system.
When C levels get too high, the cells that produce the CRF and ACTH become inhibited and less C is produced. This process is referred to as negative feedback inhibition and this is how the body monitors and controls C levels. Normal ranges vary considerably throughout the day with peak concentrations (280-720 nmol/l) reached between 7 AM and 9 AM. By 9 PM to 12 AM levels are considerably lower (60-340 nmol/l). Practically speaking does this have any significance for bodybuilders and strength athletes? A review of a the literature tells us that training in the morning versus training much later in the day will not make a difference as far as our C responses to exercise. What does make a difference however, is consistency. By lifting weights on a consistent basis, over time the body interprets this as less of a stress and produces less C as a result. This of course is assuming you are not over-training.
Functions of Cortisol
So now that we know what C is, and where it comes from, what does it do? Let's start with a basic fact: Cortisol is essential for life and is catabolic to all cells in the body except liver cells. Catabolic refers to the ability to breakdown large molecules into smaller molecules. This applies to you in the following fashion: Let's say you just got done with your two-hour leg workout. Cortisol levels will be elevated because you trained a large amount of muscle mass very intensely and for a fairly long time. The amount of muscle mass, intensity of exercise and the duration of exercise are factors that help to stimulate C production and release. Cortisol can now cause muscle proteins to be broken down into amino acids. These amino acids can travel to your liver or to the damaged muscle fibers in your quadriceps. In the liver, amino acids can be reassembled into new proteins, converted into glucose or converted into fatty acids. In the quadriceps, the amino acids can be reassembled into proteins that will help to repair the damaged muscle fibers. An interesting side effect of lifting weights is that it is antagonistic to glucocorticoid induced muscle atrophy. Exactly why this occurs is not clear, but suffice it to say that, as you gain experience with lifting weights, C is less likely to break down that muscle you worked so hard for.
Another function of C -- that most people are usually glad to hear about -- is that it breaks down fat. Fat cells around the body are referred to as adipose tissue. Cortisol helps the fat stored in adipose tissue, called triglycerides, to be broken down into smaller molecules, namely glycerol and three fatty acids. The glycerol and fatty acids can now enter the blood and be used as energy sources by other tissues in the body. The importance of this is seen during starvation where C levels are substantially elevated. The practical significance of this for the bodybuilder is that severely restricting calories will elevate your C levels to in order to breakdown fat and muscle for energy. On a side not it should also be pointed out that low calorie diet also lower your testosterone. Imagine having suppressed testosterone levels and elevated C levels. That is exactly the opposite of what we want to build muscle.
What else does C do? For the record, C also helps to: maintain blood pressure and proper renal (kidney) function; reduce swelling and speed up tissue repair; modulate perception and emotion; play a permissive role in the development of fetal organs; and directly effect bone and connective tissue growth in children. So while we may not want C levels higher than normal, we also don't want them lower than normal either. Our bodies use C for a variety of functions and by forcing it below normal through the use of drugs or supplements, these same functions can be impaired in the body.
While C breaking down fat is a good thing, you don't want to lose your hard-earned muscle with the fat. It is true that C inhibits protein synthesis (making new proteins) and can stimulate proteolysis (breaking down proteins) in your muscles, but remember the literature suggests that lowering C won't help you build muscle any faster because C appears to break down certain proteins preferentially. This means it does not break down functional proteins of muscle or nerve cells. It has also been shown that damaged tissues can use the newly acquired amino acids from the labile proteins to synthesize new proteins for tissue repair. In addition it takes a back seat to insulin and exercise. This means that eating and training intelligently not only help you look and feel better, but they counteract the catabolic effects of C.
Acute Effects of Exercise on Cortisol Response
As briefly mentioned earlier, after a workout, C levels can be elevated for up to several hours. Factors that can influence C release are the intensity of the exercise, the amount of muscle mass being trained, the length of the workout and calorie levels in your diet. It is normal for C to be released during and after a workout. At this point you may wonder, "Is this is good or bad?" Let's say you just did a heavy chest workout. Damaged muscle cells (fibers) in your chest and assisting muscle groups send out chemical signals. These signals attract special white blood cells called neutrophils. Neutrophils travel to the injured fibers and start breaking them down. In addition, specialized compartments inside of the injured muscle cells called lysosomes rupture and release proteolytic enzymes. These are proteins that will break down your hard-earned muscle. The combination of the neutrophils and enzymes degrading your muscle contribute to the muscle soreness you feel a day or two after training. Cortisol helps to reduce the accumulation of neutrophils and stabilize the lysosome compartments so that they don't rupture. Now remember when we mentioned that C stimulates amino acid release into the blood? Well these amino acids can be used to repair the injured muscle fibers. Therefore, dramatically reducing C after a workout may increase muscle soreness and delay muscle recovery.
Chronic Effects of Exercise on Cortisol Responses
What happens to your C responses after you have been lifting for several months? In a trained lifter the typical C response is lower than an untrained lifter. This holds true for runners as well. In addition, C levels after exercise return to their normal levels quicker. The benefits of this are that you get the same protective Effects of C against muscle soreness, with less protein breakdown. This assumes of course that you are not over-trained. In over-trained athletes resting C levels can actually remain increased. This can pose a problem because excessive C levels are associated with a variety of health disorders. The best thing for you to do is take a break from training and not try to artificially suppress your C levels. If you artificially suppress C, in an attempt to mask your over-trained state, you can unwillingly create other health problems with the adrenal glands that will take months to correct.
Negative Effects of Cortisol Elevation/Suppression
One problem with C is that really high levels do cause muscle wasting. However this is seen only in trauma/burn/injury/disease patients -- not people lifting weights. In healthy people, excess C is not enough to cause excessive muscle protein breakdown after a single workout. Another point is that C deficient people don't synthesize more protein than normal people. In athletes C levels can be used as markers of training status. One reason for this is that chronically elevated levels are associated with impaired performance. So the catch is: How do you prevent C levels from being high all the time, without disturbing the important functions that C is involved in? In order to answer this question let's take a look at what happens when you chronically suppress C (