The Science of Muscle Building

The Science of Muscle Building: What actually happens at a cellular level in the muscle growth process?
         The Physiology of Muscle Building

    There are two stereotypical reasons why people use a gym – to lose weight or build muscle. Despite muscle building (hypertrophy) being one of the fundamental reasons many people actually train, very few people (most personal trainers included) really know about and understand the physiological chain of events that occur after an intense resistance training session.
    Hypertrophy is a complex process involving many factors ranging from sufficient resistance exercise to hormonal response. This article will break the process down into a much simpler version, allowing you to understand a principle forming the bedrock of many trainees motivation to train.

The Hypertrophy Chain of Events

    The process starts with what is known as the ‘stimulus’ – this is the training itself. We stimulate the muscles, which causes ‘trauma’. This is the term for muscle damage – it is the breakdown of the skeletal muscle tissue. This breakdown forces the muscle to restructure and grow, returning bigger and stronger under the correct nutritional and recovery conditions.
    The trauma activates ‘satellite cells’. These cells rush to the areas in the muscle that are damaged by the training, setting in motion the chain of events that start the repair and growth of the tissues.
    Once the satellite cells are in place, they fuse together and bind to muscle fibres. This initially increases the cross sectional area of the muscle (hypertrophy). The satellite cells fuse with the muscle tissues forming new muscle protein strands called myofibrils.
    The extra nuclei (cell ‘brains’) from satellite cells allow muscle to synthesise more proteins and to create more contractile myofilaments, known as Actin and Myosin (these are the elements of the muscle cells that allow them to contract). The more contractile myofilaments we have, the stronger we are. It is for this reason that bigger muscles are usually stronger than smaller muscles, as they contain more contractile myofilaments.
    The whole process will only be successful if the body is well nourished, providing the nutrients required for muscle growth, and well rested, which provides an opportunity for the body to ensure the physiological changes and adaption can be performed and completed fully. If the body is not nourished, the new proteins and new contractile myofilaments will not be formed, leading to little or no progress in terms of muscle development for the trainee.
    The list above outlines the basic physiological steps to muscle growth. There are other factors that play a significant role in the process.

The Role of Hormones in Muscle Growth

    Hormones or hormone-like compounds in the body play a direct role in the muscle building process. We will refer to these as ‘growth factors’. The hormones stimulate satellite cells to produce gains in muscle fibre size. Clearly there is a correlation between the amount of growth factors and the ability to generate muscle tissue. It is for this reason many athletes use anabolic steroids, which are either natural or man-made hormones that artificially aid muscle building. The non-medicinal use of growth factors is dangerous and in sporting events provides an unfair advantage to athletes over those not using such substances. As a result these aids are banned by almost every sporting governing body on the planet.
    Growth factors work regulating satellite cells- the more satellite cells present, the more prolific the processes outlined above can be, and (to a point) the more muscle tissue the body can generate.
    One particular growth factor that is known to play an important role in the hypertrophy process is Hepatocyte Growth factor (HGF). Research carried out by Charge and Rudnicki (2004) suggested that it is the active factor in damaged muscle and may also be responsible for causing satellite cells to migrate to the damaged muscle area. This process aids the regeneration of muscle tissue, leading to increased gains in muscle tissue.
    Fibroblast Growth factor (FBF) is an important growth factor post-exercise. A significant body of research has concluded that FGF is responsible for the revascularisation (building new blood vessels) of the tissues during muscle regeneration. This is particularly important, as the tissue needs an adequate blood supply in order to be well nourished and to allow for the removal of waste products. The hormones and other growth factors are transported through the blood, further highlighting the necessary importance of a good blood flow to the tissues.
    Insulin-like Growth factors I and II (IGF’s) are another well-researched area of the whole process. The IGF’s play a major role in the regulation of muscle mass growth. They are responsible for promoting protein synthesis and muscle cell repair. The protein synthesis manufactures more contractile elements in the muscles, making the muscle stronger. As the strength develops, the muscle is capable of lifting more weight meaning the strength and muscle size increase process can continue until a natural plateau is reached.
    Growth Hormone (GH) is one of the key hormones in the whole process of bodybuilding. The level of GH released into the blood stream during and post exercise is largely dependent on the intensity of the exercise being performed. The hormone triggers fat metabolism for energy use in the muscle growth process, which is an obvious advantage to anyone looking to lose excess body fat. Finally, Growth Hormone stimulates the uptake and incorporation of amino acids into proteins, which are used and generated in the construction of skeletal muscle.
    Perhaps the most well known hormone of all is Testosterone. The role of testosterone in the hypertrophy process is vitally important- it stimulates Growth Hormone response to exercise, enhances cellular Amino Acid uptake and the protein synthesis in skeletal muscle. Some evidence suggests that testosterone may even regulate satellite cells. In theory, the more testosterone a person has, the higher their muscle-building capability!
    Given the obvious importance of hormones in the process, it is easy to see why competitive athletes often use performance –enhancing drugs. I feel I have spouted enough science for now, so let me tell you this…
    If you want to inject dodgy chemicals into your arse or are happy to take pills that have more than likely been manufactured in some dirty, non-professional lab, go right ahead. If, like me, you value your health and vitality, please avoid them. You don’t really want messed up hormones, corroding organs, bitch-tits, brittle bones, acne, anger management issues, testicle shrinkage, hyperhydrosis, renal failure, liver failure, enlarged heart…(I could go on) do you?

One Response

  1. How long does hypertrophy chain of events actually take. i.e. from stimulus/trauma to muscle recovery and growth?

    I recall reading somewhere that the whole process takes several days. But as you say in your HIT article, HIT advocates 2-3 fullbody routines per week, so the recovery/growth period must be quite short otherwise you’d be causing more trauma to muscles that are not yet recovered.

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