Why Do Some People Naturally Build More Muscle?

You've likely heard that everyone has a different body. Some people are built with smaller shapes, while others may have tall or curvy shapes. But how does this impact muscle building? If you've ever wondered why some people naturally build more muscle than others, you've got lots of company.

Research has shown that genetics have a big impact on how well we build muscle, points out Shape. Some people are primed to have that defined look because they're born with short tendons and long muscles, explains former exercise science director at Quincy College Wayne Westcott (per Shape). These long muscles provide a better baseline for toning, sculpting, and strengthening the muscle.

Genetics also influences the muscle fibers found in our bodies, shares CNET. Muscle fibers are made up of fast twitch and slow twitch fibers, and each of these contribute to athletic performance in their respective way. Healthline explains that fast twitch muscles help with strength training and powerlifting, whereas short twitch muscles support endurance.

Similar to tendons, some people have more of one type of muscle fiber. This is influenced by the ACTN3 gene and ACE gene, shares MedlinePlus. More specifically, when someone carries a certain variant in the ACTN3 gene, they tend to have larger amounts of fast twitch muscle fibers, which means more strength-building capacities.

However, genetics and muscle fibers aren't the end-all, be-all of building muscle as they're only part of the equation.

Hormones also play a major role in why some people naturally build more muscle. In particular, testosterone which is a major sex hormone, has a part in increasing muscle size and mass (per Healthline).

While testosterone is often associated with men, women have testosterone too. When it comes to muscle growth, its job is to communicate with the neuromuscular system and trigger protein synthesis, shares Cedric Bryant, the chief science officer for the American Council On Exercise (per Self).

While genetics affect these hormone levels, Bryant points out that training programs can affect the endocrine system so that more testosterone (and muscle-building power) is being produced (via Self). In other words, your strength training routine matters.

Heavy weights build muscle strength more efficiently and they help grow your muscles, explains Byrdie. They are generally used during power training and strength training. On the other hand, lighter weights build lean muscle, strength, and endurance.

In addition, one 2022 study reports that increasing protein levels may help enhance body composition. The researchers note that body composition may improve from a variety of diets such as a low-fat diet, keto diet, low carbohydrate diet, and more.

So, if you're wanting to build muscle mass, take heart as there are some factors that may be within your control.