Tyler Robbins Fitness

B.Sc. Biochemistry, Certified Strength and Conditioning Specialist (CSCS), Certified CrossFit Trainer (CCFT/CF-L3), USA Weightlifting Level 1


Cortisol is one of the most misunderstood hormones in the human body. Hopefully this blog will be able to help educate my readers so that they understand this very busy hormone more thoroughly.

What is Cortisol?
Cortisol is a stress-related hormone also known as a glucocorticoid, which is released by the adrenal gland in the human body. Its primary functions include: increasing blood sugar concentrations through the process of gluconeogenesis, aid in fat, protein, and carbohydrate metabolism, as well as suppress immune system function.

Role of Cortisol

Cortisol exerts catabolic effects on the body by increasing the levels of proteolytic enzymes. These proteolytic enzymes break down proteins within the body to convert them to carbohydrates while also inhibiting protein synthesis. Research has suggested that cortisol has a greater catabolic effect on Type II muscle fibers simply because they contain more protein than Type I fibers. An immense increase in blood cortisol levels can result in a net loss of contractile protein. This results in muscle atrophy which can reduce the size and strength capacity of the muscles.

Factors that Reverse the Effects of Cortisol

To create an anabolic effect within the muscle, cortisol must either be blocked or counteracted. It turns out, testosterone and insulin can counter cortisol's effects. If more insulin is bound to a cell's receptors, or if testosterone blocks the required genetic element within the cell's DNA for cortisol, protein synthesis can be conserved or enhanced. If, however, a greater number of receptors are bound to cortisol, protein can be degraded or lost.

Studies have shown a number of other factors that can reverse the effects of cortisol such as magnesium supplementation, omega-3 fatty acids, massage, laughter, etc. Through supplementation, a reduced-stress lifestyle, and regular exercise have been shown to reduce chronic levels of cortisol and make levels more manageable.

Factors That May Increase Levels of Cortisol
Research has shown that a number of factors can contribute to higher levels of cortisol. Dietary factors such as caffeine or anorexia can cause chronic increases, but other lifestyle factors such as traumatic events, a stressful commute to and from work, stressful job, lifestyle, etc. can also play a role in chronically high levels of cortisol.

Resistance Exercise Response of Cortisol

Similar to growth hormone, levels of cortisol increase as a result of resistance training. The largest increase is seen when resistance training rest periods are short and total volume is high. This may be surprising to some, but let us not forget that cortisol is released during times of stress, and resistance training places great stress on the body. Another factor to point out, is that once an individual (mostly males) have begun to 'adapt' to their training program, the testosterone produced counteracts the cortisol levels to a degree.

Interestingly enough, cortisol levels seem to spike as a result of the same factors that spike levels of growth hormone. It can then be suggested that although chronic increases in cortisol production, caused by factors such as chronic stress, etc. can have a catabolic effect on the body, shorter, acute increases brought on by resistance training must play a larger role in tissue remodeling.


Most people need to understand that since cortisol is produced by the adrenal gland, that same gland that is involved in many of the "fight or flight" processes in the body, it is no wonder that higher levels are to be expected following resistance training. One of the main roles is to be a primary signal hormone for carbohydrate metabolism which is not at all surprising either. If the body is entering a stressful situation, you essentially want to have the brain and muscles alert for 'action' so they would require higher than usual levels of carbohydrates (the body's jetfuel) for increased performance.

Unfortunately, the stresses that most people face on a day to day basis are not actually life-threatening and therefore do not actually require this type of metabolic response. Negative long-term health problems are therefore linked to stressful lives as the body stays 'alert' for far too long.

The role of cortisol from resistance exercise is still vastly unknown, although what is known is the fact that cortisol plays a much larger role in the tissue remodeling process within the body as it is released after periods of resistive exercise that places great anaerobic stress on the body. The goal of any individual however would be to lead as stress-free lifestyle as possible and allow their cortisol production be used solely for tissue growth, repair, and remodeling.