Is Muscle Protein Synthesis the Same as Growth?

Man training with weights

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Manufacturers of sports supplements and protein powders often claim that their products can increase muscle protein synthesis (MPS). While this suggests that sports supplements somehow facilitate changes in muscle mass, the process is actually more complicated than that.

Muscle growth is ultimately achieved with the combination of resistance training and protein intake. What MPS provides us is the means to gauge how effectively those interventions work. MPS is ultimately a physiological process by which increases are linked to improved muscle growth, although the actual gains can vary from one person to the next.

How Muscle Protein Synthesis Works

Protein is the building block of muscles. Muscle protein synthesis is a naturally occurring process in which protein is produced to repair muscle damage caused by intense exercise. It is an opposing force to muscle protein breakdown (MPB) in which protein is lost as a result of exercise.

The ratio of MPS to MPB determines whether muscle tissues are built or lost. If MPS outpaces MPB, muscle growth is achieved. If MPB outpaces MPS, the opposite occurs.

MPS can be enhanced by increasing your protein intake immediately following exercise. The amino acids derived from protein will then be shuttled to your muscles, replacing any lost to exercise.

Learning how to stimulate MPS through exercise and diet can help accelerate muscle growth, improve recovery and athletic performance, and increase overall endurance.

Effects of Exercise

Protein balance is used to describe the relationship between muscle protein breakdown and muscle protein synthesis. When your body is in protein balance, no muscle growth or wasting is occurring, and you're considered to be in a healthy state of biological equilibrium (homeostasis).

To stimulate muscle growth, you essentially need to unsettle the protein balance. While it may seem counterintuitive, exercise can break down muscle protein but rarely in excess of protein synthesis. In fact, the greater the intensity of a workout, the greater the MPS.

Scientists measure intensity by something called the one-repetition maximum (1-RM), meaning the maximum weight you can lift for one repetition.

According to research from the University of Nottingham, workout intensities of under 40 percent of the 1-RM will not affect MPS, whereas intensities greater than 60 percent will double or triple the MPS.

Even if exercising to failure, low-intensity exercise will do little to increase MPS and, as such, will not increase muscle mass.

Effects of Diet

The relationship between diet and protein balance is less straightforward. Even with increased protein intake, MPS is triggered for only a finite period of time. This is because the body can only utilize so much of the essential amino acids (EAAs) it receives; anything more will be broken down and excreted by the liver.

To stimulate MPS, it is important to consume the appropriate amount of protein following exercise. Eating too much will not improve muscle growth but may increase the accumulation of potentially harmful byproducts such as urea.

A study from the University of Birmingham looked into MPS response rates in men prescribed 10, 20, or 40 grams of whey protein immediately following resistance training. According to the researchers:

  • A 10-gram dose of whey protein had no effect on MPS.
  • A 20-gram dose increased the MPS by 49 percent.
  • A 40-gram dose increased the MPS by 56 percent but also caused the excessive accumulation of urea.

Consuming 20 grams to 40 grams of whey protein after resistance training also increased concentrations of phenylalanine, leucine, and threonine, EAAs associated with lean muscle growth.

A Word From Verywell

Muscle protein synthesis is not something achieved by taking a sports supplement. It is a biological process that can vary by the individual's fitness status. As such, it is not something you can readily measure or manipulate.

With that being said, there are strategies you can use to promote MPS. Start by increasing the intensity of your workout, pushing weights that require significant force but not enough to undermine proper form or personal safety. Follow up by feeding your muscles with protein. A 20-gram dose of a digestible protein drink is likely a good place to start.

If you are considering consuming protein beyond the recommended dietary intake, speak with your doctor or a registered sports nutritionist to understand the potential benefits and risks.

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