Protein Synthesis and Muscular Growth by 3J


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Understanding Protein Synthesis and Muscle Growth
By: 3J Ologys Head Sports Nutritionist
3J's Nutrition | Diet and fitness consulting to get you to the next level.

Protein synthesis is the foundation in which bodybuilding was built upon. It is the reason why we are able to grow our muscles through weight training and nutrition. The principle of weight training can be reduced to a simple sentence, lifting weights plus rest with improvement over time. But there are a number of variables that always make that principle much more complex than it seems, like nutrition. Protein synthesis is the utilization of amino acids to create proteins in the body for consumption. Alarmingly, many who participate in body building are clueless as to how muscular growth actually occurs. Lets go ahead and cover that.

Understanding Muscle Damage and Muscular Hypertrophy

Lets try to put this in the most simple terms as possible. The growth of muscle comes from muscular cell damage and the enlarging of the muscle fibers via repair. The reason we go to the gym and lift weights is because we are trying to put enough strain on our muscle fibers so that they are damaged. The damaging of muscle fibers induces the process of protein synthesis. Muscular growth is caused by hypertrophy, or the enlargement of muscle fibers. A breach in plasma member of the muscle fiber cell allows the passage of calcium from the blood causing an imbalance of calcium in the muscle vs the bloodstream. Increased calcium levels activate enzymes called calpains which remove the damaged pieces of the muscle (easily releasable myofilaments). Furthermore, ubiquitin (a protein that is present in all muscle cells) binds to the removed filaments causing neutrophils (white blood cells) to attack and destroy the filaments. As this process occurs, monocytes enter the damaged muscle and from macrophages which further handle the destruction of damaged tissue (1). Ironically, macrophanges also active satellite cells for muscular repair. We will come back to satellite cells in a moment.

So, we have covered how the body gets rid of the damaged tissue. Lets talk about how muscles grow. There are many nuclei in muscle cells. Each nuclei can only handle so much protein at a time and the number of nuclei in a muscle is directly correlated in how much growth can occur. Lets go back to those satellite cells. Satellite cells are stem cells that attach to muscle, donating their nuclei to the muscle through the process of proliferation (the increase of satellite cells) and differentiation (becoming more like muscle cells) (2). When the wall of muscle cells are damaged, growth factors are released to allow the process of proliferation and differentiation. Remember that hypertrophy means the growth of the fiber and should not be confused with hyperplasia, or the increase in the number of fibers in the muscle (3).

The main two major growth factor released are FGG (fibroblast growth factor) and IGF-1 (insulin-like growth factor 1). FGF is released from the cell and causes proliferation of satellite cells (4) while IGF-1 causes satellite cells to differentiate, causing them to fuse with muscle cells and allow for growth (hypertrophy). Protein synthesis occurs because mRNA (a genetically coded substance) is sent out from the nuclei to ribosomes which then being the building of protein from amino acids (5).

Prostaglandins and Satellite Cells

Prostagladins are a group of lipid compounds that have hormone like effects. For the purposes of this article we shall only focus on PGE2 and PGF2-alpha(a)since they are most significant to growth. During contraction and stretching of muscle fibers a number of prostaglandins are released including PGE2 and PGF2-a. PGF2-a increases protein synthesis while PGE2 increases protein degradation. Ironically, PGE2 is also a major player in inducing satellite cell proliferation and infusion. The more satellite cells available for activation, the greater the potential for growth (8).

Protein Synthesis

Lets go back to the phase of muscular repair where the mRNA (messenger RNA, a coded substance) is released by the cell to begin the process of protein synthesis. The mRNA has the correct instructions to activate ribosomes and instructs ribosomes to begin translation (the assembly of amino acids). tRNA (transfer RNA) then takes over, arranging amino acids in a linear fashion to create the protein given in the initial instructions by mRNA. This is the process in which we actually gain hypertrophy of the muscle fiber (6).

Testosterone and Protein Synthesis

Nothing is more naturally anabolic than testosterone, it directly causes protein synthesis. Testosterone binds to the androgen receptor in cells which causes activation of protein synthesis in the nuclei. Testosterone also increases the sensitivity of IGF-1 and FGF to satellite cells. The act of resistance training has been shown to increase the receptive capability of testosterone and other important hypertrophy factors like GH and IGF-1. Protein synthesis is said to last anywhere from 36 to 48 hours after strenuous exercise (7).


There are two types of IGF-1. Autocrine IGF-1 is made locally in cells while paracrine IGF-1 is made in the liver. Autocrine IGF-1 only affects the tissues in the area in which it is released while paracrine IGF-1 can travel through the bloodstream into different tissues of the body, connecting to receptors on the surface of cells that specifically need its presence to trigger an anabolic effect. Autocrine IGF-1 is what does the business for bodybuilding. Recall that damage to the muscle causes calcium to leak into the cells. Its this same calcium that releases autocrine IGF-1 locally and sets off the process that is protein synthesis. A mixture of IGF-1, calcium, and enzymes all allow the protein synthesis but also depend on calcium to make the process begin (5).

The IGF-1/HGH Connection

The main contributing anabolic factor of human growth hormone is that it causes the cells in the liver and muscle fiber to release IGF-1. It triggers paracrine IGF-1 to be released from the live and autocrine IGF-1 from muscle cells. One can now understand why the combining of HGH and testosterone causes a much more efficient anabolic response. GH releases IGF while testosterone binds to the androgen receptor and increases the receptive capability of IGF and FGF to satellite cells. Satellite cells give their nuclei to muscle fiber and allow for an increased capacity for protein synthesis causing the end goal of every bodybuilder, muscular hypertrophy!

1. Pedersen, B. K. Exercise Immunology. New York: Chapman and Hall; Austin: R. G. Landes, 1997.

2. Hawke, T.J., and D. J. Garry. Myogenic satellite cells: physiology to molecular biology. Journal of Applied Physiology. 91: 534-551, 2001 satellite cells

3. Russell, B., D. Motlagh,, and W. W. Ashley. Form follows functions: how muscle shape is regulated by work. Journal of Applied Physiology 88: 1127-1132, 2000. Hypertrophy

4. Adams, G.R., and F. Haddad. The relationships among IGF-1, DNA content, and protein accumulation during skeletal muscle hypertrophy. Journal of Applied Physiology 81(6): 2509-2516, 1996. FGF

5. Fiatarone Singh, M. A., W. Ding, T. J. Manfredi, et al. Insulin-like growth factor I in skeletal muscle after weight-lifting exercise in frail elders. American Journal of Physiology 277 (Endocrinology Metabolism 40): E135-E143, 1999. IGF

6. Alberts, Bruce (2002). Molecular biology of the cell. New York: Garland Science.

7. Vermeulen, A., S. Goemaere, and J. M. Kaufman. Testosterone, body composition and aging. Journal of Endocrinology Investigation 22: 110-116, 1999 test
8. Appl Physiol Nutr Metab. 2006 Dec;31(6):782-90.
Satellite cell proliferation and skeletal muscle hypertrophy.
Adams GR1.

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3J, Ologys Head Sports Nutritionist


New member
Great right up. A lot of guys get the roids part, but don't understand how important nutrition is. If you don't understand both, don't bother.


New member
This also illustrates just how important it is that we train hard enough to CAUSE DAMAGE. When we workout half assed and barely do damage its literally a waste of time.


Super Moderator
This also illustrates just how important it is that we train hard enough to CAUSE DAMAGE. When we workout half assed and barely do damage its literally a waste of time.

Yup.. it also supports more full body workouts for beginners who want to build a foundation but thats a whole other article in itself! lol

this isn't the final draft though.. i will be going deeper into each sub catagory


avi changes as i do
Nice article 3J! What about cortisol & it's affect on muscular hypertrophy. Any way to avoid high cortisol or it negative effect on muscle gain/size?? I'll shut up & listen, thanks


avi changes as i do
Cool. I'm not sure but I feel like that stuff is what has kept me from better size gains in the past. Can't wait to read on...


Super Moderator
Cool. I'm not sure but I feel like that stuff is what has kept me from better size gains in the past. Can't wait to read on...

we know cortisol pretty much eats up muscle fiber through glycogenasis... the actual process itself is lofty to explain.. itll be a good addition

but the short answer is, rest and a relatively stress free life is beneficial to the body builder lol