How is Muscle Built?

A foray into the world of building muscle

Everyone wants to get healthy and put on muscle. It makes you look good, and it’s key to a healthy life. But what actually is a muscle, and how does it grow?

Many different muscle fibers make up a single muscle. Each fiber is a single cell, containing thousands of sarcomeres. The impulse to contract the muscle starts here. Each sarcomere contains actin and myosin, called contractile fibers (1). When your brain sends a signal to your muscles to move, the fibers contract, which causes the actual movement. Growing the size of your muscles, also known as muscle hypertrophy, is the process of creating new contractile fibers in each muscle fiber. This process also has the effect of increasing the strength of the muscle (1).

Cross-section of a muscle fiber. https://medium.com/@avatarnutrition/the-science-behind-muscle-growth-a1b5e9cba225

The building of muscle is regulated by both the mammalian target of rapamycin (mTOR) mechanic and the amount of available protein in the body. When muscles are used, they sustain damage—for example, your muscles become sore after a workout or hard run (1, 3). During the recovery, the mTOR protein is activated, causing muscle protein synthesis (MPS). Your body is in an anabolic state when building new muscle (1). However, muscle building requires an excess of protein in the body. If there is not sufficient protein, the body breaks the muscle down to retrieve the stored proteins, also known as being in a catabolic state (1).

Because proteins cannot be synthesized by the human body, they must come from an individual’s diet. High-protein foods such as meats and dairy are key for improving muscle growth (2). Muscle growth is also aided by hormones, such as testosterone, human growth hormones, and insulin. These hormones work by inhibiting the breakdown of muscles, and increasing both the synthesization of protein and creation of new tissues (2, 3).

Because of the many factors involved in muscle growth, different people will have different rates of hypertrophy. Since men have a much higher testosterone level than women, they will grow muscle more rapidly and lose muscle slower (2, 3). Scientists also have different classifications of body types based on how easy it is for the person to gain muscle mass. Mesomorphs are typically muscular, have a lower body fat, and easily build muscle. Ectomorphs are typically skinny, and have a hard time building muscle. Endomorphs usually have a higher body fat, but easily build muscle (2). But despite the different rates at which people may put on muscle, anyone can build muscle if they put their mind to it.

Different body types for both men and women. https://www.precisionnutrition.com/all-about-body-type-eating

But why is having muscle important? Increasing your lean body mass (LBM) can have drastically positive effects on your health (1). The body stores excess protein in muscles; so, if your body needs extra protein to heal or recover, it can use the protein stored in your muscles. Since muscles also consume calories, a higher LBM can also increase your metabolic rate (1). Finally, a higher LBM is correlated with a lower chance of contracting age-related diseases, such as osteoporosis and osteoarthritis (2).

Muscle building is a complex process. It requires many different mechanisms in your body and proper exercise and diet. But, although many people want to gain muscle for superficial reasons, it can also have amazing health benefits.

Sources:

  1. Avatar Nutrition. (2018, February 19). The Science Behind Muscle Growth – Avatar Nutrition – Medium. Medium. https://medium.com/@avatarnutrition/the-science-behind-muscle-growth-a1b5e9cba225
  2. Leonard, J. (2020, January 8). How to build muscle with exercise. Medicalnewstoday.com; Medical News Today. https://www.medicalnewstoday.com/articles/319151
  3. How Do Muscles Grow? (2024). Unm.edu. https://www.unm.edu/~lkravitz/Article%20folder/musclesgrowLK.html