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Friday, March 22, 2013


One of the subjects most talked about in the fitness and nutrition world today is stress, and what could be done to improve and minimize its levels. The problem is that due to the busy lifestyle, information received each minute of the daily life, and the obstacles that are encountered, the human brain is working overtime to process everything, which is causing stress levels to increase no matter how old you are. When talking about stress, everyone assumes cortisol levels as being high because reduced levels are part of the 70% (Ratios to Success) to get your desired results and might be the factor that is keeping you from them.

But is Cortisol really that bad for the body? What is the role of cortisol in the body? What is its effect with resistance training?

 As explained in “Where’s the beef? Meathead!” the endocrine system produces cortisol (glucocorticoid hormone) in a similar manner as the production of Amino Acids by the cortex of the adrenal glands (located above the kidneys). After the translation of the RNA messenger from the cholesterol molecule, the pre-hormone is transferred into the endoplasmatic reticulum (structure inside the cell that synthesizes proteins), where cortisol is produced by the Golgi apparatus. It is considered a steroidal hormone because its chemical structure is similar to that of cholesterol just like the sexual hormones. The release of cortisol is controlled by the brain (hypothalamus-pituitary) which triggers its secretion in response to stress providing energy to overcome metabolic disturbances of homeostasis (equilibrium of bodily functions). It is usually released as soon as it is produced and transported by the blood to control the metabolism of proteins, carbs and lipids (fats) to maintain homeostasis.

Under normal circumstances (non-stressed), cortisol secretion has its high and low peaks during the cycle of day and night (circadian rhythmicity), where its concentrations are at their highest in the mornings decreasing throughout the day into the night. They become elevated again a few hours after sleep. The purpose of natural cortisol release is to regulate energy and mobilize it to maintain homeostasis. It participates in the metabolism of carbs, by stimulating glucose formation (glycogen) increasing blood glucose levels; protein metabolism in the catabolic process of breakdown of muscle, skin and bone, releasing AA into the blood; and fat metabolism by stimulating lipolysis (fat breakdown) with the release of fatty acids and glycerol while preventing fat synthesis. It also has effect when injuries occur or when the immune system is being attacked. When the response of other adrenal hormones are not enough to stop the stress, cortisol is released so that it can use fuels, in form of carbohydrates, proteins and fats stored in the body to produce energy for recovery.

Cortisol is secreted due to psychological or physical stress or when our organism suffers a certain type of strain or pressure setting off the fight or flight physiological response. This stress response begins with the release of catecholamines (adrenaline/epinephrine), and if the stress continues then the brain activates the hypothalamus to activate the kidneys to release more cortisol into the blood stream to mobilize energy reserves. The release of extra cortisol produces immediate effects of increase in HR and Blood Pressure (BP), rapid breathing and intake of more oxygen, and the redistribution of white blood cell, reducing the immune system activity. The excess amount of cortisol stops the utilization of energy, and it increases fat stores and circulation of fat in the blood which could cause obesity and other disease related high body fat percentages.

With the modern lifestyle any factor could cause psychological stress when you find yourself in a new situation that is unpredictable and uncontrollable.  Studies confirmed without doubt that the levels of cortisol increase with aerobic and resistance training, because it is a stress on the body where adaptation is needed to return to homeostasis. This increase occurs at an intensity of 60% or higher, but there is no evidence of what the duration of an exercise session is to produce excess levels that would affect results negatively. What defines the levels of cortisol produced to be excessive causing the increase muscle breakdown (catabolism) and prevent muscle synthesis jeopardizing muscle mass increase and fat reduction would be the intensity of the training session. Cortisol affects Type II muscle fibers more than Type I in short rest period/high volume training sessions. After a training session, during early recovery, the amount of cortisol increases in attempt to maintain blood glucose levels which affects skeletal muscle and adipose tissue for the increase of AA and lipid mobilization. It also stimulates the liver for catabolism and transfer of glycogen into energy. Therefore the tools and methods used to minimize excess levels of cortisol for recovery (nutrition and rest) should be taken into consideration.

There have been studies showing that cortisol reduces testosterone levels during exercise, but this is because they present at similar levels and not because there is less testosterone, so cortisol isn’t always the taboo in preventing you from your results. It just might be your periodization, bad eating habits and lack of recovery methods.
Articles Consulted:
Cortisol and Growth Hormone Responses to Exercise at Different Times of Day. Kanaley et al. J. of Clinical Endocrinology and Metabolism. 2001.
Basic Endocrinology. Taylor & Francis. E-library. 2005
How to measure stress in humans.  Fernand-Seguin Research Center. 2007.
Relationship between circulating cortisol and testosterone influence of physical exercise. Brownlee, Moore and Hackney, Journal of Sports Science and Medicine. 2005.

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