During exercise, the body releases the hormone cortisol to provide glucose for the body. Cortisol derives glucose by breaking down protein found in muscles. This results in muscle loss, since the body is using muscle protein instead of carbohydrates for fuel. Regulating cortisol levels helps decrease muscle loss while increasing the body's ability to build muscle.
Function
The body releases the hormone cortisol in response to daily stressors or apparent threats. It's part of the body's "fight or flight" reaction to stress. As MayoClinic.com explains, cortisol increases the mobilization of glucose into the bloodstream and boosts the brain's ability to use glucose. In addition, it downgrades activity in the immune, reproductive and digestive systems. Cortisol levels are amplified during and after exercise because of the stress that training places on the body.
Exercise Variables and Cortisol
Research shows that intensity and duration are two exercise variables that affect the amount of cortisol released. In a study published in the "Journal of Strength and Conditioning Research," subjects performed low-, moderate-, or high-intensity exercise for an hour. Scientists found that subjects performing high-intensity exercise for a long duration increased their cortisol levels much more than did the other groups. They concluded that exercising at a low or moderate intensity level for a short or moderate duration can keep cortisol levels in check.
Cortisol and Time
In a study published in the "Journal of Clinical Endocrinology and Metabolism," researchers had subjects exercise at 7 a.m., 7 p.m. and midnight. They recorded cortisol levels one hour before exercise and five hours afterward. The researchers found that cortisol levels were significantly higher before and after exercise with subjects who exercised at 7 a.m. compared with those who did so at 7 p.m. or at midnight. They concluded that exercising in the morning can increase cortisol levels.
Side Effects
When the body is overwhelmed with stress for too long, it releases a substantial amount of cortisol to combat the stress. Overexposure to cortisol can increase the risk of depression, obesity, digestive problems and heart disease. For that reason, it's important to find ways to reduce stress.
Recommendation
After training, the body is in a catabolic, or muscle-wasting, state due to the rise of cortisol. At this time, the body is using protein from muscles for fuel instead of fat or carbohydrates. This results in muscle loss until the body switches back to an anabolic, or muscle-building, state. One way to shift the body from catabolism to anabolism post-exercise is by taking branched-chain amino acid supplements. According to the "Journal of Strength and Conditioning Research," subjects ingesting branched-chain amino acids for three weeks while performing high-intensity exercise decreased their levels of cortisol, a catabolic hormone, and increased their levels of testosterone, an anabolic hormone.
References
- Mayo Clinic: Stress Management
- Molecular and Cellular Endocrinology: The Effect of Cortisone on Protein Breakdown
- Journal of Strength and Conditioning Research: Effect of Exercise on Salivary Cortisol
- Journal of Clinical Endocrinology and Metabolism: Cortisol and Growth
- Journal of Strength and Conditioning Research: Amino Acid Supplements
