Welcome to the third and last part of the complex series of articles on the science behind muscle growth. In case you missed the previous articles, here they are: Part 1 and Part 2.
Today we will discuss about the main substances that can influence the muscle building process, and these are:
IGF-1 – This comes in 2 types: paracrine IFG-1 which is primarily created in the liver and autocrine IGF-1 which is produced locally within other cells. The first one functions by travelling through the body via the bloodstream to the many tissues scattered around the body.
Autocrine IGF-1 works in a different way. It tends to stay in the local area and it only affects the tissues within that area when it is released. The receptors located on the surface of the cells are vital for Paracrine IGF-1 to enter them and for the anabolic effects to take place. But Autocrine IGF-1 works differently because it is manufactured and excreted in response to high-tension contractions and operates independently from the receptors on the surface as it is already on the inside. Once it makes its way inside the cell, the IGF-1 has interaction with enzymes that are activated by calcium, and triggers a process that results in protein synthesis.
A major contributory factor to increasing the protein synthesis is the IGF-1/calcium/enzyme complexes which help the process at the ribosomes more efficient. Furthermore, insulin works at the ribosome in an almost identical manner hence where the name ‘Insulin-Like Growth Factor-1’ comes from. Therefore I recommend taking quick digesting carbs immediately after your workout to raise the insulin levels.
GH – is believed to work by causing the liver and muscle cells to release IGF-1. An effective training session causes GH levels to rise in the bloodstream, and this in turn triggers the liver to release paracrine IGF-1 a few hours later. This also triggers the muscle cells to release autocrine IGF-1 which leads to the induction of effective muscle growth.
Prostaglandins – these are released during the contraction and stretch phase of exercise. The most important ones related to muscle growth are the PGE2 and PGF2-alpha. PGE2 increases protein degradation whereas PGF2-alpha increases protein synthesis.
PGE2 is also powerful in terms of inducing satellite cell proliferation and infusion. Despite numerous long studies into the mechanism behind PGF2-alpha it is not very clear what it does, but it is suspected to assist in increasing protein synthesis efficiency at the ribosomes.
Testosterone - ‘Free’ testosterone in particular travels freely throughout the muscle cells’ membranes and once it reaches inside, it activates what is known as the ‘androgen receptor’. On the other hand, ‘Bound’ testosterone must activate the receptors on the cell surface before it is enabled to enter. As soon as the androgen receptor is activated by testosterone it travels all the way to the nucleus and immediately triggers the protein synthesis process.
Testosterone directly induces the protein synthesis and is known to be the most powerful anabolic agent found inside the human body. It also helps to increase the satellite cells’ sensitivity levels to IGF-1 and FGF, thus promoting the proliferation and differentiation of satellite cells.
Testosterone also increases the body’s systematic output of GH and IGF-1 and a weight training session will cause a spike in T-levels. Muscle cells are more receptive to Testosterone, systemic IGF-1 and GH immediately after a workout.
And finally, the whole process of cellular damage and any subsequent overcompensation (the cells grow back slightly bigger than before) can typically take from several hours all the way up to several days, depending on how severely you trained. Studies have revealed that experienced individuals have shown to complete the protein synthesis process cycle within a 36 – 48 hour timeframe after an intense bodybuilding workout. This suggests that muscles should be trained every 48 hours.
To conclude, it is clear that increasing the volume of muscular contractile elements is key to increasing muscle size and strength. Type II fibers area have the greatest potential for muscle growth and strength because they contain the most actin/myosin filaments and generate the highest tensions.
So you must ensure that you lift heavy enough weights to recruit the type II fibers, but also make sure that you subject them to that tension for long enough in order for significant damage to occur to muscle fibers.
About The Author: James McDuffy works for "The Muscle Growth Expert". You can visit his website for more info on different aspects of bodybuilding and the science behind muscle growth.
Published by Craig Wilson