Cortisol

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.

Summary

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.

Anabolic Hormones Part 2: Growth Hormone

Last week we discussed the anabolic hormone testosterone. This week, part 2 of 3, will focus on growth hormone.

What is Growth Hormone?

Also known as "somatotropin", growth hormone comes from the pituitary gland. It has many different uses and anabolic effects within the human body which can have direct effects or mediated through the production of insulin-like growth factor-1 (IGF-1) by the liver and fat cells.

What Does It Do?

Growth hormone is present and very important in the growth and development of children, but has also been seen as a result of resistance training. The tissues that growth hormone interact with include bones, immune cells, skeletal muscles, fat cells, and liver tissues. The main physiological roles are:

-Decreases glucose utilization
-Decreases glycogen synthesis
-Increases amino acid transport across cell membranes
-Increases protein synthesis
-Increases utilization of fatty acids
-Increases fat breakdown
-Increases availability of glucose and amino acids
-Enhances immune cell function

How Does it Work?

As one of the most potent anabolic hormones, growth hormone may me mediated by secondary hormones, but for the most part, it acts directly on target tissues. It interacts with tissues and stimulates the release of IGFs which greatly increase the conditions that promote tissue repair.

Growth hormone is released from hepatic (liver) cells as well as non-hepatic cells (fat, white blood cells, muscle, etc.) and enters peripheral circulation. It is transported in this way so that it can attach to specific binding proteins on cells.

Pharmacological Growth Hormone

Due to the varied uses of growth hormone in the human body, it is still unclear as to why pharmacological growth hormone acts differently than exercised-induced growth hormone. One thing that has been researched and documented however is that injecting growth hormone into an individual may increase muscle hypertrophy (size) but this may compromise the quality of muscle being built. For still-unknown reasons, exercised-induced hypertrophy is a much more favorable technique for gaining mass while also maintaining muscle quality and strength.

Program Design

If an individual is training for hypertrophy purposes, their program design is very important in order to reach their goals. Studies have shown that increased blood lactate concentrations increase the level of growth hormone. One thing to note however, is that when individuals were studied using very light weights and exercising in a much higher repetition range, serum levels of growth hormone did not change. There appears to be an intensity limit for individuals to reach in order to stimulate growth hormone production.

On the other hand, individuals who were training with heavy resistance (10 rep maximum) with short rest periods between sets (1 minute) saw greater growth hormone concentration increases when compared to individuals training in the 5 rep maximum range with longer rest periods. This has been studied and documented before and should be of no surprise as strength or power training (very high reps, 5 or fewer reps) works very well to increase and individual's overall strength, but a 6-12 rep range is ideal for muscular growth.

Growth Hormone in Women

Studies have shown that women have higher blood levels of growth hormone throughout their menstrual cycle compared to men. This not only proves that growth hormone plays many different physiological roles within the human body, but also that it is not the single limiting-factor when it comes to muscular growth. This may be due to the fact that women generally have lower levels of testosterone, but other factors must also be at play when determining what causes muscular hypertrophy.

Summary

Although there have been many studies done on the effects of both exercised-induced, as well as pharmacological growth hormone, there are still many variants and observations that need to be done. It is understood that there are multiple interactions that growth hormone plays a role in that determines muscular growth and strength as it has been shown that simply increasing concentrations does not necessarily increase muscle size/strength. Also, understanding how growth hormone concentrations change throughout not only an individual's day to day life, but also over long periods of resistance training can help us further understand the full role this anabolic hormone plays in our bodies.

-Tyler Robbins
B.Sc. CSCS

Sources:
Baechle, Thomas R. and Earle, Roger W. Essentials of Strength Training and Conditioning Third Edition