Is Muscle Protein Synthesis the Same as Growth?

Understanding the Role of MPS

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Muscle protein synthesis (MPS) is often mentioned in articles or discussions surrounding muscle growth. It has become a popular term among athletes, bodybuilders, and fitness enthusiasts. Supplement and protein powder manufacturers will market an increase in MPS using their products. We may even consider MPS and muscle growth as the same thing, and this is where a bit of confusion exists. We understand MPS has something to do with muscle growth but not quite clear what it really means.

It’s important to understand the role of muscle protein synthesis (MPS) to maximize muscle growth.

What Is Muscle Protein Synthesis (MPS)?

Muscle protein synthesis (MPS) occurs as a response to resistance exercise or nutrition intake. During intense workouts, our muscle tissue breaks down stimulating amino acids through muscle protein synthesis to repair the damage. When we eat protein sources, amino acids from these foods are shuttled to our muscle tissue replacing any muscle protein losses occurring in a fasted state or as a result of oxidative stress. Overall, the primary function of muscle protein synthesis is to help repair and build new muscle tissue.

Muscle protein synthesis (MPS) can also be described as a biological process that occurs in our muscle tissue and other parts of the body. According to research, it’s the driving force responsible for how our body responds and adapts to intense exercise.

MPS is also variable depending on the type of exercise performed and nutrition consumed, specifically protein.

How Does It Affect Muscle Growth?

Learning how to effectively stimulate muscle protein synthesis (MPS) through resistance training and adequate protein intake will help promote lean mass gains, improve muscle recovery, and energy.

This will be a different process for each individual based on physical activity imposed, genetic makeup, and food intake. Maintaining protein balance also plays an important part in MPS for muscle growth.

According to research, the two primary variables determining protein balance in our muscles include physical activity and nutrient availability. This understanding allows us to apply the best exercise and feeding methods to maintain and build lean mass.

The Importance of Protein Balance

Protein balance is maintained through a dynamic process of muscle protein breakdown and muscle protein synthesis (MPS). The best scenario is when a positive protein balance is sustained. This means MPS activity is greater than muscle protein breakdown, allowing for muscle growth to occur. Contrarily, a negative protein balance can lead to deterioration of muscle tissue.

Research indicates our body is in a constant state of muscle protein breakdown and synthesis. Muscle protein balance is usually kept in check because of these continual processes. When our body is in protein balance, no muscle growth or wasting is occurring and considered a healthy state of homeostasis. This is typical of most active individuals exercising regularly and eating right.

Active adults and athletes performing intense exercise programs can be at greater risk of creating a negative protein balance. In order to keep muscle protein on the positive side, proper training and protein intake are shown to be essential. Manipulating muscle protein synthesis through exercise and diet will help promote muscle growth, improve athletic performance, and enhance muscle recovery.

How Exercise Regulates MPS

According to research, muscle protein synthesis (MPS) is stimulated by resistance exercise or training. The amount of MPS response in muscle tissue appears to be dependent upon both workload and intensity.

Studies indicate resistance training below 40 percent of one rep maximum doesn’t really activate an MPS response. However, when exercise intensity was greater than 60 percent of one rep maximum, MPS measured a two- to threefold increase from the baseline value. These findings indicate heavy training loads provide greater stimulation of MPS.

Does this mean low-intensity exercise isn’t beneficial for muscle growth? Not exactly, and depending on workload can actually be just as effective.

Low-intensity exercise can stimulate muscle protein synthesis (MPS) according to research. Studies show exercise intensities of 30 percent of one rep maximum completed to muscle failure stimulated the same amount of MPS as heavy resistance training. Performing low-load exercise to failure is said to stimulate muscle protein synthesis and an alternate approach to muscle growth without heavy weightlifting.

Other research indicates muscle protein synthesis (MPS) response and rate differ per person. Evidently, MPS increases are short-lived and peak during resistance training compared to an untrained state. This would indicate a smaller MPS response during heavy workloads. It’s suggested increased MPS amounts and duration after resistance training is regulated by an individual's training status. This means some may experience more MPS response and others may be diminished. Studies are ongoing for more conclusive information.

According to research published in Physiological Reports, a combination of resistance training (RT) plus protein intake results in greater stimulation of muscle protein synthesis (MPS). This means physical training is great for muscle growth, but adding amino acids through protein feeding works even better. So, what is the best way to regulate MPS through nutrition?

Regulating MPS Using Nutrition

Research indicates nutrient availability plays a primary role in stimulating muscle protein synthesis (MPS) for muscle protein balance and growth. Dietary protein sources supply essential amino acids (EAAs) essential for these processes. When our muscle cells are depleted of amino acids through periods of not eating or oxidative stress, consuming foods high in protein helps keep our body in balance.

Studies show a ‘fasted-loss/fed-gain’ cycle is a dynamic muscle protein balance process helping us maintain our lean mass gains. What appears to provide the greatest benefit is consuming essential amino acids (EAAs) throughout the day, but especially post workout. In addition to when we eat it, the type of protein and amount are indicated to greatly influence the response of MPS following exercise. Of these factors, the amount of protein consumed after physical training is shown to stimulate maximal MPS during muscle recovery.

A research trial was conducted to examine how consuming 20g or 40g of whey protein influenced muscle protein synthesis (MPS) on resistance trained men post workout. The men were grouped according to lean body mass percentage and participated in two trials, consuming 20g of whey protein after whole-body resistance training and repeated after a week break using 40g whey protein. Lab tests were administered including muscle biopsies, DEXA scans, and blood workup. Some of the results of the study indicated the following:

  • Plasma leucine concentration was greater with 40g whey protein dose for both groups compared to 20g. Leucine is an essential amino acid (EAA) and branch-chained amino acid (BCAA) primarily responsible for muscle growth and development.
  • Plasma phenylalanine concentrations were higher, consuming 40g compared to 20g whey protein. Phenylalanine is an amino acid and precursor for tyrosine, one of the 20 amino acids used by the body to make protein.
  • Plasma threonine concentrations were higher with 40g consumed whey protein compared to 20g. Threonine is an essential amino acid (EAA) obtained from dietary protein sources and helps with muscle growth.
  • Muscle protein synthesis (MPS) rate showed an overall increase of 20 percent consuming 40g compared to 20g whey protein following whole-body resistance training in young men.
  • Muscle protein synthesis (MPS) was stimulated at the same rate with 40g whey protein for young men with lower and higher lean body mass following whole-body resistance exercise.

It appears 40g of whey protein ingested after resistance training could be an optimal dose to maximize muscle protein synthesis (MPS). However, other research indicates 20g of protein is sufficient to effectively stimulate MPS for muscle growth. It’s also indicated consuming 20g of protein during each meal and spaced throughout the day is the most beneficial approach to increased MPS and lean mass gains.

Another study was conducted where 48 healthy resistance trained men consumed 0, 10, 20, or 40g of whey protein isolate immediately after exercise. Muscle protein synthesis (MPS) response rates were measured over a 4-hour period. The following results indicated:

  • Muscle protein synthesis (MPS) was stimulated at a 50 percent greater rate with 20g whey protein compared to ingesting nothing.
  • MPS increased by 20 percent with 20g whey protein compared to consuming 10g.
  • There was no difference in MPS stimulation when 20g or 40g of whey protein was consumed.
  • MPS stimulation appears to be sufficient at 20g of whey protein ingested after resistance training.

A Word From Verywell

Manipulating muscle protein synthesis (MPS) for enhanced muscle development continues to be a challenge. At the very least we have discovered ingesting between 20g to 40g protein post-workout stimulates muscle protein synthesis (MPS). We have also learned how exercise, especially resistance training, plays an important role in stimulating MPS for muscle growth. Each population, older active adults, for example, will have differing MPS responses to both exercise and protein intake.

Because of these variables, future studies are recommended to narrow the scope of how exercise and nutrition influence MPS specific to differing exercise modalities, body types, and genders. If you’re considering additional protein intake beyond recommended dietary requirements for muscle growth, a discussion with your physician or registered sports nutrition expert would be a great idea.

Sources:

Atherton PJ, et al., Muscle protein synthesis in response to nutrition and exerciseJournal of Physiology, 2012

Damas F et al., A review of resistance training-induced changes in skeletal muscle protein synthesis and their contribution to hypertrophy, Journal of Sports Medicine, 2015

Macnaughton LS, et al., The response of muscle protein synthesis following whole‐body resistance exercise is greater following 40 g than 20 g of ingested whey protein, Physiological Reports, 2016

Mitchell CJ, et al., Acute Post-Exercise Myofibrillar Protein Synthesis Is Not Correlated with Resistance Training-Induced Muscle Hypertrophy in Young MenPLoSOne, 2014

Witard OC, et al., Myofibrillar muscle protein synthesis rates subsequent to a meal in response to increasing doses of whey protein at rest and after resistance exercise, American Journal of Clinical Nutrition, 2014

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