Increasing muscle volume is in the rise. More and more people are entering the gym and drinking protein shakes in order to have the physique they desire, a physique characterised by having big muscles.

But, how do we actually grow muscles? The answer is mTOR (Mammalian Target of Rapamycin), which the Fitness Genes DNA analysis is helping us to understand. Analysing the mTOR gene, they are able to identify the activity of the signalling pathway (as mTOR encodes the mTOR protein).

So, what is mTOR? It is a molecule that regulates protein synthesis, cell growing and ageing. When we do a bout of resistance exercise, the muscle fibres and cells send a signal to grow bigger muscle, which is regulated by mTOR. When people go to the gym and lift heavy weights in order to grow muscle, what they effectively do is activate the mTOR molecule. Digestion of the essential amino acid leucine also activates mTOR (hence the use of protein shakes).

Normal cells, hypertrophy is an increase in cell size, hyperplasia results from an increase in cell number. different. Vector diagram for educational, medical, biological and science use. Courtesy of

Growing muscle is called hypertrophy, which is an enlargement of the cross-sectional area of muscles fibres. This can be achieved by increasing the number and size of the myofibrils (the structures in the muscle that contract), increasing strength, or by increasing the volume of fluids and non-contractile proteins (sarcoplasmic hypertrophy), however this doesn’t lead to an increase in strength, it just increases the size.

A positive net muscle protein balance is needed to increase muscle mass. This means that there is more muscle protein synthesis (creation of proteins from amino acids) than muscle protein breakdown (breakdown of proteins into amino acids). Here mTOR is the master regulator. It stimulates muscle protein synthesis, and leads to an increase of muscle mass, if other factors (protein intake, energy balance, nutrient availability...) are correct.

But, the benefits from understanding mTOR are not limited to bodybuilders, endurance athletes (most of the people reading this) can benefit from it too. Our adaptation pathways (PGC-1αvia AMPK) inhibit the activation of mTOR. But, we need mTOR for two main reasons. First, for some athletes (time trialists, rouleurs...) gaining slow-twitch fiber muscle mass is desired, in order to gain absolute power for those terrains. Activating mTOR after a ride (either introducing strength training or consuming leucine/leucine-rich protein) and staying in a positive energy balance can achieve that increase in power. Second, repaired muscle replenishes glycogen faster than damaged muscle, so activating mTOR (via leucine ingestion) will repair that muscle faster, leading to faster recovery (faster glycogen replenishment). Ingesting leucine on top of high glycemic-index carbohydrates will lead to a faster replenishment of glycogen when needed.

Understanding mTOR, and knowing how to adjust training and lifestyle in order to maximize it, given  what our predisposition to mTOR activity is (via Fitness Genes test, for example), alongside working with professionals that understand the new science of epigenetics such as Spokes coaches, will lead to an optimization of your time to address your personal condition and ultimately achieve your goals. 

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