Virtually everything you do in life triggers a hormonal response in the body. Hormonal levels control our body's actions. It is very important to understand the key role hormones play in inducing muscular growth as well as muscular breakdown.
Hormones are chemical messengers that are secreted by the endocrine system. Once they are in the blood they travel to specific receptor sites on cells. Tissue adaptions are partly dependent on hormonal levels. It is important that the athlete has a basic understanding of these powerful messengers. Manipulating these hormones to your advantage ensures successful adaption, training, health and performance.
Muscle Fiber Changes
The most important adaption that takes place in muscle tissue is the increase in contractile proteins, actin and myosin. Other changes occur such as the synthesis of non-contractile proteins (satellite cells), which can become part of the contractile element of muscle tissue. Stimulation of these mechanisms occurs with resistance training. Decreasing protein breakdown and increasing protein synthesis are the first steps in hypertrophy.
The anabolic hormones insulin, insulin like growth factor, testosterone and growth hormone are all contributing factors to this process. Decreasing the catabolic hormones such as cortisol is also important in this process. The more muscle fibers stimulated with a particular exercise, the greater the adaptive response. Hormones have a great effect on the capabilities and structure of muscle fibers.
The lock-and-key theory states that a specific hormone interacts with a specific receptor site. The hormone acts like a key while the receptor site is like a lock. Once the key opens the lock, a message is sent to the cell to perform a specific action. The genetic material in the nucleus of the cell either translates the message to mean protein synthesis or protein breakdown. Once an adaption ceiling is reached, the cell becomes down regulated (non-responsive) to the hormone. Down regulation of the receptor inhibits alteration in cell metabolism.
Two Main Hormones
There are two main categories of hormones: steroid and polypeptide hormones. These hormones affect muscle cells in different ways.
The gonads and the adrenal cortex secrete steroid hormones. The hormone diffuses across the sarcolemma and binds with its receptor, thus activating it. When the hormone reaches the cell nucleus it opens up units that are coded for protein synthesis. The hormone receptor-complex recognizes certain regulatory mechanisms of genes. The end result is that messenger RNA is processed and shuttled to the sarcoplasm where it becomes protein.
Polypeptide hormones are made of amino acids. Growth hormone and insulin are example of this classification. These hormones are not fat-soluble therefore they cannot penetrate the sarcolemma. They rely on secondary messengers to get their message to the cell nucleus. The change in the receptor as a result of the interaction with the hormone triggers the secondary messenger. A chain of intracellular events lead to the physiological response contributed to the hormone.
Heavy Resistance Exercise
Heavy resistance exercise stimulates significant adaptions in trained muscles such as increased strength, size and power. Resistance training causes endocrine glands to secrete hormones. These hormones provide an excess of information to the body. These hormones elicit different responses. The pattern and duration of exercise greatly influence the type of hormone secreted.
This in return greatly effects the tissue adaptions that occur. Hormonal increases that take place due to resistance training are different than responses activated by endurance exercise. Motor units are utilized with resistance training that are not with other types of exercise. These high threshold motor units are only activated when great amounts of force are needed, such as with heavy resistance training. The muscle fibers within these motor units are activated and a great amount of stress is placed upon the sarcolemmas of the muscle fibers. The stress elicits changes in sarcolemma permeability to nutrients and synthesis and sensitivity of receptors are affected. Finally, it is the force produced in the activated fibers that lead to the anabolic response in the muscle cells.
During and following exercise, numerous hormonal secretions take place. The desired outcome is synthesis of actin and myosin and inhibition of protein breakdown. If the stress is to great or long in duration, catabolic forces such as cortisol take over the muscle. The hormonal responses depend on tissues stimulated, duration of exercise and needed amount of repair.
Once a muscle has reached a high level of development, protein synthesis is no longer the key mechanism for growth. Thus decreasing protein breakdown is the number one contributor to muscular growth. Keep in mind that only the muscle fibers stimulated are subject to affect. This is why it is important to vary exercises. Only the fibers stimulated receive hormonal benefits. If you use the same exercise for biceps every time you train, you will not maximize growth because the same fibers are stimulated continuously. Angles and loading parameters control the extent of hormonal interaction within muscles.
The response of muscles to hormones is dependent on a few factors. If there are great amounts of the hormone in the blood, the chances of affecting the receptors are greater. If the cell is close to its genetic ceiling, the receptor becomes less responsive to the hormone. With heavy resistance training the recovery ability correlates with muscle fiber size. Incorrect training protocols can result in the downside of hormones, catabolism. Interactions between hormones and muscles can negatively influence cellular structure or have a positive effect on growth.
There is an array of factors that contribute to hypertrophy. However, increased force production cannot be contributed to hypertrophy alone. Neural factors play a great role in maximum force production. Each individual varies in forms of neurological efficiency just as they do with hormonal levels.
Hormones In Blood
Blood levels are sometimes used to test for the secretion of hormones. This can be a complex task because the hormonal levels are ever changing in the bloodstream. It should be noted that just because a hormone is present in the bloodstream does not mean that it will successfully reach the receptor site. Although, the higher concentrations of the hormones in the blood the greater possibility for the hormone to bind to the receptor.
The ideal situation for anabolism is to have a higher number of anabolic hormones in the blood than catabolic hormones. This usually leads to positive cellular adaptions.
This concludes Part One of the two part series on manipulating your hormones. In part two, we will explore the specific actions of the primary anabolic and catabolic hormones.
Note: This is part one, click here for part two!