Cortisol is a steroid hormone, and is probably the most underrated hormone by fitness professionals. Cortisol is catabolic, in that it has the opposite effect of testosterone, insulin and growth hormone. Cortisol breaks down tissue versus building it up. Cortisol is released by the adrenal glands when the body is under high mental or physical stress and high temperatures. Cortisol has three main functions:
The reduction of protein synthesis
The facilitation of protein to glucose
The halting of tissue growth.
These three function explain why it is important to control cortisol release. Simply, if you want to grow your muscles, you need to control cortisol in your body. The amount of cortisol released is mainly determined by your fitness level. Individuals just beginning to exercise are going to release more cortisol initially, but when they become more adapted to the stress of exercise and the body becomes comfortable, the amount of cortisol released will decrease.
Different types of training will elicit a different cortisol response. Weight training has primary goal of building muscle mass and cardiovascular training has the goal of building cardiovascular endurance. These different styles of training will cause different hormonal changes to occur. Aerobic training is going to lower testosterone and cause higher cortisol levels than weight training. This is primarily why, at the level of the hormones, that aerobic exercise is limited when trying to put on muscle mass. Weight training works in the opposite manner. Higher levels of testosterone and lower levels of cortisol are going to be present and is the main reason why our muscles grow (hypertrophy). The body responds in this fashion because larger muscles are needed to exert the necessary amount of strength and endurance for that specific activity. Also the intensity of the exercise will determine the amount of cortisol released.
One of the most important things to remember is that when it comes to cortisol and food intake, is that when glycogen (stored carbohydrates) are too low, cortisol is going to go up. Carbohydrates are the body’s number one source of energy, so when this source is really low, the body has to begin to pull fuel from other sources (the only other two sources are protein and fats). These rising cortisol levels will stimulate the breakdown of proteins and lean tissue into amino acids (building blocks of muscle) to be converted into glucose (carbohydrate). The rising levels will also stimulate the breakdown of fatty acids in the fat stores, making more body fat available to be used as fuel. In order to prevent this from happening, athletes need to keep their glycogen stores as full as possible and make carbohydrates the bulk of your food intake.
When it comes to exercise duration, more is not always better. Training too much and too frequent can actually cause strength and gain losses due to the elevated cortisol. Listening to the body and following the basic principles of weight training and make your diet spot on will ensure that you do not overdo it because too much of a good thing isn’t always the best for you.
So in summary, don’t over train, listen to your body, rest up, fuel up appropriately, and have fun. In past Knowledge posts, I’ve described all of these elements so go back a read some. If you have questions, you can always send me an email.
