Cortisol is one of the many hormones produced by the body. It is sometimes called a stress hormone, because a fight-or-flight reaction may trigger the adrenal gland to increase its production. Cortisol, which is also produced during aerobic exercise, has a catabolic effect on muscle tissue, which means it is associated with muscle breakdown.
Function
During aerobic exercise, cortisol production is increased in proportion to the duration and intensity of the workout, exercise physiologist Dr. Len Kravitz says in an article on the University of New Mexico website. Cortisol also preserves carbohydrate stores during prolonged aerobic exercise. It also facilitates the process that transforms protein into glucose.
Misconceptions
Since cortisol production increases during aerobic exercise and since increased cortisol has a catabolic effect on muscle tissue, some bodybuilders believe aerobic exercise is detrimental to their sport. Bodybuilding coach and certified personal trainer David Robson, owner of Elite Physique Training Studio, disputes this theory. In an article on the BodyBuilding.com website, he argues aerobic exercise also releases endorphins, the "feel-good" hormone, and the endorphins can counteract the negative effects of cortisol. Shawn Talbott, author of "The Cortisol Connection: Why Stress Makes You Fat and Ruins Your Health," says extreme aerobic exercise without proper recovery is what increases cortisol production. Moderate aerobic exercise may even decrease cortisol in sedentary women, reports Dr. Kursat Karacabey, lead author of a study published in the 2005 edition of "Endocrinology Letters." His team tested women before and after 30 minutes of treadmill exercise.
Prevention/Solution
Nutrition plays a key role in preventing excess cortisol production during aerobic exercise. Dr. Kravitz says carbohydrates fuel aerobic exercise. Insufficient carbohydrate intake will cause the body to produce cortisol in order to catabolize protein for aerobic exercise fuel.
Theories/Speculation
Cortisol production during high-intensity aerobic activity may also be associated with anxiety. A 2002 article in "Outside Online" details the research associated with this subject. Apparently, anxiety stimulates cortisol while increasing glucose production and heart rate. Anxiety is future-oriented. During a normal run in the park, you would not be concerned about the outcome of your workout. Your body will eventually begin producing adrenaline, creating a feeling of exhilaration. If you suddenly realized a gang of teenagers was chasing you, your brain circuitry would change. Mary Meagher, the behavioral neuroscience psychologist interviewed for the article, says anxiety increases cortisol production, but decreases adrenaline, leaving you frightened, but not exhilarated. A racer, competing for an important event, may experience a similar type of anxiety.
Warning
When caused by overtraining, improper nutrition and inadequate recovery, excess cortisol production as an adverse effect on the immune system.
References
- "Essentials of Strength Training and Conditioning"; Thomas R. Baechle, Roger W. Earle; 2008
- BodyBuilding: The Implications of Cortisol Release
- Trifuel: What is Cortisol?
- Outside Online: At Home in the Discomfort Zone: The battle of the Butterflies
- Neuroendocrinology Letters: The Effects of Exercise on the Immune System and Stress levels in Sportswomen
- University of New Mexico: The Role of Cortisol in Concurrent Training
