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What is the role of protein synthesis in muscle growth?

What is the role of protein synthesis in muscle growth?

If you are interested in building muscle, you may have heard of the term protein synthesis. But what does it mean and how does it affect your muscle growth? In this blog post, we will explain what protein synthesis is, how it is stimulated by exercise and nutrition, and how you can optimize it to achieve your muscle goals.

What is protein synthesis?

Protein synthesis is the metabolic process that describes the incorporation of amino acids into bound skeletal muscle proteins. Muscle proteins can be crudely classified into the contractile myofibrillar proteins (i.e., myosin, actin, tropomyosin, troponin) and the energy producing mitochondrial proteins. The synthesis of myofibrillar proteins is primarily responsible for changes in skeletal muscle mass following resistance training, whereas mitochondrial proteins are primarily synthesized in response to endurance type training .

The measurement of protein synthesis is most commonly expressed as a rate of amino acid incorporation into bound muscle protein over a given time period, typically a single hour or a single day. Conversely, the metabolic process of muscle protein breakdown describes the degradation of bound muscle proteins into their amino acid precursors that occurs continuously and concurrently with protein synthesis. As such, the aggregate difference in rates of protein synthesis and muscle protein breakdown determines whether muscle protein is gained (protein synthesis exceeds muscle protein breakdown) or muscle protein is lost (muscle protein breakdown exceeds protein synthesis) .

How is protein synthesis stimulated by exercise?

Exercise can stimulate both protein synthesis and protein breakdown, depending on the type, intensity, duration, and frequency of the exercise. Resistance exercise, such as lifting weights, causes mechanical stress and microdamage to the muscle fibers, which triggers a cascade of molecular signals that activate protein synthesis. Resistance exercise also increases blood flow and amino acid delivery to the muscles, which further enhances protein synthesis .

The magnitude and duration of the protein synthesis response to resistance exercise depends on several factors, such as the volume and intensity of the exercise, the muscle groups involved, the training status of the individual, and the recovery period between bouts. Generally speaking, a single bout of resistance exercise can increase protein synthesis by 50–100% for up to 24–48 hours after exercise . However, this response can vary widely among individuals and may decline with repeated bouts of exercise due to adaptations in the muscle .

How is protein synthesis affected by nutrition?

Nutrition plays a crucial role in modulating protein synthesis and muscle growth. Protein intake is essential for providing the amino acids that are needed to build new muscle proteins. Protein intake also stimulates an anabolic hormone called insulin, which further enhances protein synthesis and inhibits protein breakdown .

The amount, type, timing, and distribution of protein intake can influence the protein synthesis response to resistance exercise. The optimal amount of protein intake for maximizing protein synthesis after resistance exercise has been estimated to be around 0.25–0.4 grams per kilogram of body weight per meal, or about 20–40 grams for most people . However, this amount may vary depending on individual factors such as age, sex, body composition, training status, and dietary preferences.

The type of protein also matters for stimulating protein synthesis. Protein sources that contain all nine essential amino acids (EAAs), especially leucine, are more effective than those that lack some EAAs or have low leucine content. Animal-based proteins, such as whey, casein, egg, meat, fish, and dairy products, are generally high in EAAs and leucine and have been shown to elicit greater protein synthesis responses than plant-based proteins, such as soy, pea, rice, and hemp . However, plant-based proteins can still support muscle growth if they are consumed in sufficient amounts and combined with other complementary sources to provide adequate EAAs and leucine.

The timing of protein intake relative to resistance exercise can also affect protein synthesis. Consuming protein before or after resistance exercise can increase protein synthesis by providing amino acids to the muscles during or after exercise . However, there is no clear evidence that one timing strategy is superior to another for enhancing muscle growth over time . The most important factor is to consume enough total daily protein to meet your needs and distribute it evenly throughout the day.

How can you optimize protein synthesis for muscle growth?

To summarize, here are some practical tips to optimize protein synthesis for muscle growth:

Engage in regular resistance exercise that challenges your muscles with sufficient volume and intensity.

Consume enough total daily protein to meet your needs based on your body weight, activity level, and goals.

Choose high-quality protein sources that contain all nine essential amino acids and leucine.

Consume protein before or after resistance exercise to stimulate protein synthesis and support muscle recovery.

Distribute your protein intake evenly throughout the day, aiming for about 0.25–0.4 grams per kilogram of body weight per meal.

By following these tips, you can maximize your protein synthesis and muscle growth potential and achieve your fitness goals.

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: Witard OC et al (2014) Myofibrillar muscle protein synthesis rates subsequent to a meal in response to increasing doses of whey protein at rest and after resistance exercise Am J Clin Nutr 99:86–95

: Gorissen SHM et al (2018) Protein content and amino acid composition of commercially available plant-based protein isolates Amino Acids 50:1685–1695

: Schoenfeld BJ et al (2017) Pre-versus post-exercise protein intake has similar effects on muscular adaptations PeerJ 5:e2825

: Schoenfeld BJ et al (2013) The effect of protein timing on muscle strength and hypertrophy: a meta-analysis J Int Soc Sports Nutr 10:53

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