Wondering if “bad chest” genes are real?

The answer is yes, sort of. But it depends on what you consider bad genes. What one person considers bad another person might consider good.

Your genes are units of genetic information that you inherit from your parents. They determine all your inherited traits from your eye color to your bone structure. Environmental factors such as nutrition, exposure to chemicals, and exercise habits can change the way some genes are expressed.

You can build muscle by engaging in resistance training. But genetic factors can influence how easily you add mass. Likewise, genetics can influence how easily you build muscle in a particular area such as your chest.

Keep reading as we take a look at how genetics affect your ability to build muscle in your chest.

“Bad chest” genes are subjective. Many people use the term to refer to having difficulty building muscle in their chest or difficulty building muscle with the aesthetics they want.

The bulk of your chest is made up of the bellies of your pectoralis major muscles, commonly referred to as your “pecs.” These muscles originate from your sternum and collar bone and insert into your upper arm.

Some people consider “bad chest” genes as having a large gap between their pectoralis major muscles or having an asymmetry between each side of their chest.

Do some people have better chest genetics than others? It depends on what your goals are and what you consider “bad” genetics.

Some people can build more muscle or build muscle at a faster rate in their chests than others. Genes play a role in the following factors:

  • Total number of muscle fibers: One group of researchers, who labeled people as either men or women, found that the number of muscle fibers in the quadriceps of nine men from ages 15 to 22 years old varied from 393,000 to 903,000. Large variations would also be expected in other muscles such as the pectoralis major.
  • Muscle fiber types: Your muscles are made up of thinner slow-twitch fibers and thicker fast-twitch fibers. The ratio of these fibers varies drastically between people, and it’s not clear how much you can shift your ratio through training.
  • Tendon insertion: Your tendons are the pieces of connective tissue that connect muscle to bone. Having longer tendons where your pectoralis major muscles attach to your sternum may make it more difficult to fill in the center of your chest with muscle.
  • Size of muscle belly: Likewise, having a larger pectoralis major muscle body may make it easier to fill out your chest.
  • Bone structure: The shape of your rib cage plays a role in determining how thick your chest appears. Some birth abnormalities such as pectus excavatum can cause your sternum to grow inward and give your chest a sunken appearance.

Researchers are continuing to examine genes that play a role in building muscle mass. In one rodent study, researchers identified 47 genes linked to muscle growth.

Twin studies suggest that more than 50% of muscle fiber composition is estimated to be inherited from your parents.

Body dysmorphia is a mental health condition characterized by preoccupation with your body’s flaws. Muscle dysmorphia is a specific type of body dysmorphia characterized by a persistent worry that you’re not muscular or lean.

Becoming preoccupied with the size of your chest could be a symptom of muscle dysmorphia. The Muscle Dysmorphic Disorder Inventory is often used as a testing tool with 13 questions that are scored from “never” to “always.” Some of the statements on this inventory include:

  • I hate my body.
  • I find my chest to be too small.
  • I wish my arms were stronger.
  • I am embarrassed to let people see me without a shirt.
  • I miss opportunities to meet new people because of my workout schedule.

In a 2018 study, researchers compared rates of muscular dysmorphia between bodybuilders, strength athletes, and people engaged in general fitness. They found that bodybuilders reported more beliefs about being smaller and weaker than the other groups.

Learn more about how muscle dysmorphia is diagnosed and treated.

A chest gap is the separation of your pectoralis major muscles. It’s normal to have a chest gap since there’s no muscle body over your sternum. Some people have wider gaps than others as part of their natural anatomy, which is largely predetermined by genetics.

It’s important to remember that the idea of “bad genetics” is subjective. If your goal is to build as much muscle as possible, you might consider bad genetics as having more trouble building muscle than other people around you.

But for some people, not adding muscle mass with training might be considered good genetics. For example, athletes in weight-class sports such as boxing or relative strength sports such as long jump need to build a large amount of strength without adding much extra weight.

You can’t change your genetics, but you can change the way your genes are expressed by changing your training program. Consistently training your chest muscles can help you maximize your muscle size and strength. Some people find it helpful to work with a personal trainer who can build them a custom program to help them achieve their goals.

Some men opt to get pectoral implants, but these are primarily meant for people with birth deformities, such as pectus excavatum. People with muscle or body dysmorphia are not candidates for pectoral implants.

The best way to grow your chest is by training your chest muscle regularly. Many different exercises can target your chest. Here are some ideas:

Your genetics influence your ability to build muscle. The idea of “bad genetics” is subjective. If your goal is to build muscle, your genes might make it easier or harder than most other people to build muscle in general or specifically in your chest.

The best way to maximize your chest growth is to train your chest regularly. You may find it helpful to work with a personal trainer who can build you a custom program.