Understanding functional anatomy and the endocrine system is paramount to optimize exercise performance in a safe and effective manner. Some terms to be familiar with include:


1.       Endocrine glands, which are the body structures responsible for secretion, storing and releasing of hormones. 

2.       Hormones, which are essentially  the body’s’ messengers

3.       Neuroendocrinology which is the terminology which describes the relationship between chemical substances that have both neural and hormonal functions. 

4.       Target Tissues (peptide hormones): hormones in the blood that carry messages to hormone-specific receptors.  

5.       Steroid Hormones: hormones that directly affect the DNA in the nucleus (center) of the cell.

6.       Autocrine secretion of a hormone means the cell releases the hormone itself (automatic).  It may be stimulated to do so by an external stimulus (hormone). In response to exercise, insulin-like growth factor I (IGF-I) is released inside the muscle cell to cause the cell to produce more myofibrils.

7.        Paracrine secretion involves the release of a hormone to interact adjacent cells, without a need for circulation of the hormone in the bloodstream

Understanding functional anatomy and the endocrine system is paramount to optimize exercise performance in a safe and effective manner.

The role of hormone receptors in the body is extensive as they control several variables which are critical to muscle function, growth and recovery, including; how much blood-to-tissue shift occurs with exercise, the amount of cell synthesis and storage of hormones. They also control the transport of hormones via binding proteins, the time needed for hormones to clear through the liver and other tissues, how tightly the hormone binds to its receptors and how saturated the tissues are with these receptors. The magnitude of the signal sent to the cell via secondary messenger right down to the amount of protein that is produced and what rate of degradation there is within the muscles.

Exercise causes a shift of body fluids from the blood to the cells.  This shift in fluid results in an increased concentration of hormones in the blood, which can affect the receptor interactions. 

Resistance exercise training that uses high volume, large muscle groups and short rest periods result in increased serum cortisol amounts. Though chronic high levels of cortisol may have adverse catabolic effects, which break down muscles, acute (short term) increases may contribute to the modeling and creation of muscle tissue. For this reason, training styles must be varied to allow the adrenal gland to engage in recovery processes to take advantage of the initial benefits provided by cortisol but prevent the secondary responses of cortisol, which can negatively affect the immune system and protein composition. 

Growth hormone is primarily responsible for tissue regeneration and is produced by the anterior pituitary gland and is a “polypeptide” that consists of 191 amino acids. It stimulates the release of another hormone called “somatomedin” by the liver, thereby causing growth.  Excessive growth hormone production in children can lead to gigantism, and in adults, it can lead to acromegaly. Interestingly, the release of growth hormones often cycles around the circadian rhythm, with females producing more than males. The two biggest factors that affect the release of growth hormone are:


1.       Sleep

2.       Exercise


The type of exercise also impacts the amount of growth hormone released.

Resistance Training provides a very conducive environment for Exercise-Induced Growth Hormone Release (EIGR) with the major factors including load and frequency.  When lifting heavier loads at a greater frequency (with reduced recovery time) the body will produce more growth hormone.

Endurance Training, when performed at a frequency above the lactate level for 10mins, will produce a greater growth hormone release for up to 24 hours afterward. However, when endurance training lasts for longer periods of time it can actually have a negative impact reducing the amount of growth hormone produces and increasing the amount of cortisol in the body.

Insulin is a peptide hormone which is produced by beta cells in the pancreas and is considered an anabolic hormone, regulating carbohydrates, fats, and protein by promoting the absorption of glucose. Insulin circulated around the blood affects the synthesis of protein in the muscle tissues, conversely, low insulin level has a catabolic effect where muscle tissue breaks down due to the protein being converted into fat cells for more readily available energy sources.  

In order to adhere to best practice, it is important for health professionals to familiarize themselves with the endocrine system and advise their clients to train within the limits that their body is capable of. Establishing a balance where ultimately, growth hormone levels supersede cortisol levels is essential to maintain muscle mass long term. Excessive exercise shouldn’t contribute to anybody’s’ stress, especially with the associated increased cortisol levels and their catabolic effects. It is hard work to build muscle mass and it would be disheartening and frustrating for anyone to train to a point that they break down the muscle they have worked so hard to build. Ignorance is no longer an acceptable justification to hold back results. As a professional, it is your job to work with your clients to achieve their goals. Knowledge is power so read up and share the wealth generously with those willing to learn. Train smarter NOT harder.




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Taz Dunstan

Taz Dunstan is a loving mum of two, business owner of XL Personal Training, a fitness professional, sponsored athlete, health and wellness ambassador, author and presenter. With over 15 years of fitness industry experience she has a wealth of knowledge which she is passionate about sharing with the world.

Tazs' passion for health and fitness has seen her diversify her specialties from athletics and rowing to scuba diving, rock climbing, functional training and mountaineering. Despite several achievements, including summitting Mt Acongagua, in Argentina, in 2018, her greatest achievement is being a strong role model for her children and empowering people to empower themselves to establish sustainable lifestyle choices.

Above all Taz wants to impart a strong message that everyone should own their choices and have a cause greater than themselves.

"If you have the ability to help someone, do it!" Taz Dunstan.


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