Protein & Muscle Protein Synthesis Explained

Protein & Muscle Protein Synthesis Explained

You need dietary protein to build muscle.


Protein is one of the three macronutrients (fat & carbohydrates) needed for optimal health and physical performance. 

Proteins are compounds composed of one or more long chains of amino acids. Think of these individual amino acids as the building blocks of a protein. Amino acids, individually, do not have to be digested, they go immediately into the bloodstream. This is where intra-workout nutrition, BCAA/EAA, comes into play. 

Upon digestion, protein is ultimately broken down into amino acids. There are 20 amino acids in total, and 9 of these are considered ‘essential’ meaning the body cannot make them. They must be consumed through one’s diet: Leucine, Histidine, Tryptophan, Glycine, Valine, Threonine, Lysine, Methionine, & Threonine.

Proteins perform hundreds of different roles within the body, mainly relating to repairing and building body tissue.

Muscle Protein Synthesis

Muscle protein synthesis (MPS) is the process the body undergoes to repair and increase the size of muscle. This is rooted in the biological laws of adaption. The tissue will, in theory, grow stronger/bigger (pending the stimulus from training) to overcome future physical stressors. The body is using the amino acids as fuel to grow and repair the damaged tissues.

During training, you are literally breaking down your muscle tissues (catabolic). Through proper nutrition, you enter into a relatively constant positive state of MPS (anabolic). Post training, you always want to be in positive MPS.

It’s important to note the distinction between ‘Hypertrophy’ (Increasing the existing tissue size at the cell level) and ‘Hyperplasia’ (increasing the amount of tissue).

Hypertrophy is what occurs following resistance training, not hyperplasia. You’re repairing and building upon what you already have, rather than causing cells to ‘proliferate’ and increase in number.

Hyperplasia on the other hand is determined by our hormones, such as thickening of the endometrium during menstruation, or breast enlargement during pregnancy.

Hitting the weights causes damage to our muscle tissue and needs to be repaired. The substrate used for this repair are the dietary amino acids we consume through food.

When you eat a protein-dense food, the digestive process breaks the long chains of amino acids into individual ones. These can then be re-synthesised into a new protein chain, which serve as the foundation to repair the damaged muscle tissue. 

MPS is a complex process and there’s still a lot we don’t know. What we do know is that a molecule known as ‘mTOR’ triggers the process when enough amino acids are present, and along with the help from the hormones Testosterone, growth hormone and IGF-1; protein synthesis has everything it needs to begin.

*It must be noted, their is academic debate on whether hyperplasia can occur because of weight training. However, the mechanism to which it occurs is fact.

Hyperplasia, the actual creation of the new proteins, comes in two parts and happens within the muscle cell. The first is the process of ‘Transcription’, wherein a molecule known as Messenger Ribonucleic acid (RNA) replicates the DNA information within the muscle cell nucleus. 

The second part is called ‘Translation’, and it’s here that the mRNA takes the above information to a part of the cell called the ribosome. Along with the help of ‘Transfer nucleic acid (tRNA) which corresponds to coding delivered by mRNA, individual amino acids are strung together to make a full protein chain. 

Finally, ‘satellite cells’ (a type of stem cell that sits on the muscle surface) are thought to donate their nucleus to the newly synthesized protein to create a new cell. The subsequent repair results in a bigger muscle. 

Below is a simplified diagram of the process.

Understanding how protein functions and what it’s made of is important, but equally important is understanding how much & the quality you need and the differences between types.


Stimulating MPS has a limit, you can only stimulate it so far at once, the law of diminishing returns. Meaning, one cannot consume 500g of protein and expect increased muscle mass. This limit is known as maximization, and the closer you get to MPS maximization, the stronger the effect and the more muscle you’re able to build. Go excessively over will cause GI distress and protein to be absorb as fat.

The scientific consensus in regard to maximizing MPS in one day has been determined as 0.8g per pound of bodyweight.

To find out what this means relative to your own body, simply times your body weight in pounds by 0.8. For example, a 160lbs male would consume a protein intake of 128g per day.


In the case of protein intake, both quantity and quality matter. But what denotes a protein’s quality?

Protein quality is determined by the amount, ratio and balance of the essential amino acids profile. The more essential amino acids are contained in a serving of the food or meal you’re eating the better, and you also want these amino acids to be balanced and in equal amounts if possible (as to ensure you are not lacking any).

It should be noted, this is strictly in reference to the amino acid profile of the protein. Obviously, a ribeye steak from organic, free-range cows is a better quality meat than turkey from the local deli. 

However, while yes you can get 20g of protein from rice (which is a lot of rice), it will be lacking the amino acid profile found in a standard protein shake that also contains 20g. 

The most important amino acid (although all are important), is ‘Leucine’. 

It’s responsible for triggering mTor, which as we learned earlier, is responsible for kickstarting MPS. 

Research has determined that 3-4g of Leucine is required to maximally stimulate MPS, so try to get at least 3g per serving. Leucine can be found in any complete protein so no need to ravage through nutrition labels to find it.


Protein timing has most commonly been associated with you needing to guzzle down your protein shake post-workout. While protein after a workout is certainly beneficial, academia reveals there is no difference between doing the above or eating several hours later. The real debate is concerning carb consumption at intervals pre, intra & post-workout. However, that topic is for another day. 

MPS is primed for maximal stimulation for around 24 hours following training, so as long as you consume a protein-laden meal relatively soon after, you’ll be fine. 

Having said this, contemporary research concludes it is best to consume at least four, small, protein dense meals per day, which will stimulate MPS as much as possible within 24 hours. Spread your meals out as evenly as you can, and your body will figure out the rest.

MPS is stimulated multiple times per day, rising rapidly after the consumption of a protein dense meal (providing an adequate resistance training protocol is in place) and gradually returning to baseline afterward. Once at baseline, it can then be stimulated again.

Practical recommendations

Consume ENOUGH Protein, Not Excess 

0.8g of protein per pound of body weight, per day, is more than enough to maximize MPS as far as the scientific literature is concerned. It helps to use a fitness tracking app to total all your meals and daily protein intake, but you can of course log in a journal if you wish. Again, eating excessive protein can cause digestion stress and lead to excess calories, which would be stored as fat. 

Eat Evenly 

Splitting your daily protein intake into 3 or 4 meals a day ensures you are stimulating MPS as much as you can during the day. You are also increasing the bioavailability of the nutrients you consume so your body can use the food towards energy production, tissue repair, glycogen storage, etc.... Meal prepping helps here, and means you can distribute portion sizes easily.

Eat Quality Protein

Take note of the quality of meat you consume. Low-grade lunch meat or options from some fast food restaurants will have high protein content but they could come at a caloric cost. Typically, these options are paired with other physique killing ingredients such as refined carbohydrates or hydrogenated fats. 

If you follow a plant based diet, the culinary realm has made great strides in improving protein options. Tofu flavor has progressed immensely and beans, nuts, lentils and even pastas can be combined together to make a meal with a premier amino acid profile.

The supplement industry’s greatest advancement might be the vegan protein flavoring. Plant-based protein powders will have a grittier taste compared to the frothiness of whey. However, plant options have been shown to be just as anabolic.

Whatever your diet preference or lifestyle, stick to these simple rules, and you’ll provide your body with the building blocks it needs to build a show stopping physique. Just make sure you’re hitting the iron hard, too!

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Linden Garcia Pepworth is a Sports Nutritionist (BSc Sports Nutrition) and YMCA Accredited Instructor. He is currently working on a review comparing the anabolic differences between plant and animal proteins.

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