Cortisol and Overtraining

by Rick Steiger

Many negative physiological changes occur as the result of stress and overtraining. Symptoms of overtraining include elevated resting heart rate, loss of appetite, lethargy, weight loss and irritability, as well as changes in the testosterone and hormones involved in a stress response. While a threshold level of stress is necessary to elicit the positive changes that athletes desire from their training, such as increased muscle mass and power, an enhanced cardiovascular system, and increased endurance. But what exactly occurs when the training is too stressful and they begin to experience those undesirable changes?

Research shows that testosterone levels are temporarily decreased as a result of overtraining, while serum cortisol levels increase. Cortisol is a hormone that is released by the adrenal glands in response to all kinds of stress, including exercise. The primary role of cortisol is to help mobilize energy for the body by increasing protein breakdown. Cortisol also impedes the entry of amino acids into muscle cells for protein synthesis, and instead helps to transport them to the liver to be used for energy. Other drawbacks to elevated cortisol levels are:

• Loss of bone mass through increased calcium excretion and less calcium absorption
• Adversely affects tendon health, potassium excretion (which can lead to muscle cramps in training)
• In runners and cyclists testosterone levels decreased by 50 percent and cortisol levels increased approximately threefold after intense competition
• Prolonged high levels of Cortisol can throw the immune system into chaos

Another one of cortisol�s undesirable effects for athletes is that it causes insulin resistance by decreasing the rate at which insulin activates the glucose uptake system, likely because of a post-insulin receptor block.

These changes in hormone balance are disadvantageous and sometimes disastrous for an athlete. The more educated you become about your training or overtraining the higher the gains, so keep track of your body's signals and avoid the pitfalls that come from overtraining too intensely.

Tags: abs balance calcium cardio cortisol exercise health heart hormones immune muscle potassium protein stress tea testosterone training