Is Muscle Protein Synthesis the Same as Growth?

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When trying to optimize muscle growth, protein intake is essential. But you are limited by how much protein you can synthesize to repair and grow your muscles. This brings into question the importance of protein timing and amounts and how to best stimulate muscles to grow.

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 more complicated than that.

Muscle growth is ultimately achieved with the combination of resistance training and protein intake. MPS provides us 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.

Keep reading to learn more about how muscle protein synthesis works, and what you can do to boost your ability to grow muscle.

How Muscle Protein Synthesis Works

Protein is the building block of muscles while muscle protein synthesis is a naturally occurring metabolic process in which protein is produced to repair muscle damage caused by intense exercise. This occurs from amino acids binding to skeletal muscle proteins and can lead to increased muscle size. It counteracts muscle protein breakdown (MPB) due to protein loss that happens during exercise.

The breakdown of muscles sounds negative, but it is a necessary part of building muscle. When muscles are damaged, they will build back larger, so long as you consume enough calories and protein to repair and grow the muscle tissue.

The ratio of MPS to MPB determines whether muscle tissues are built or lost. If MPS outpaces MPB, muscle growth is achieved. If breakdown outpaces synthesis, then the result can be muscle loss.

MPS can be enhanced by increasing your protein intake immediately following exercise. The amino acids 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.

The Effects of Exercise

Protein balance describes the relationship between muscle protein breakdown and muscle protein synthesis. When your body is in protein balance, no muscle growth or wasting occurs, and you're considered in a healthy state of biological equilibrium (homeostasis), otherwise known as maintenance.

To stimulate muscle growth, you essentially need to unsettle the protein balance. While it may seem counter-intuitive, exercise can break down muscle protein but rarely more than the amount of protein you can synthesize. In fact, the greater the intensity of a workout, the greater the MPS. Remember that this muscle breakdown stimulates the repair and growth of muscle tissue.

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% of the 1-RM will not affect MPS, whereas intensities greater than 60% 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.

The Impact of Food

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.

Sports nutritionists recommend about 1.4 to 2.0 grams of protein per kilogram of body weight per day for those trying to build muscle and strength.You can obtain enough protein through your diet by focusing on dairy, eggs, lean meats, nuts, and legumes.

It is also wise to consume plenty of whole grains, healthy fats, fruits, and vegetables to help your body perform and repair properly. For instance, carbohydrates are necessary for muscle building since they stimulate insulin release—a hormone that aids muscle cells in absorbing protein.

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. Researchers noticed the following results:

  • 10-gram dose of whey protein: No effect on MPS
  • 20-gram dose: Increased the MPS by 49%
  • 40-gram dose: Increased the MPS by 56% but also caused the excessive accumulation of urea

Consuming 20 grams to 40 grams of whey protein after resistance training also increased phenylalanine, leucine, and threonine concentrations, EAAs associated with lean muscle growth. Note that whey protein is a fast-digesting protein. Further results can likely be obtained by consuming slower digesting protein throughout the day.

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, you can use strategies 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 consider consuming protein beyond the recommended dietary intake, speak with your doctor or a registered sports nutritionist to understand the potential benefits and risks.

8 Sources
Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Darla Leal
Darla Leal is a Master Fitness Trainer, freelance writer, and the creator of Stay Healthy Fitness, where she embraces a "fit-over-55" lifestyle.