For some lifters, building an impressive chest is simply a matter of dialed-in training, nutrition, and recovery.

Others have additional challenges to overcome. Namely, genetics. 

Genes play a big role in the look (and strength) of the chest muscles. This can be a problem for those without the blessing of Arnold-level chest genetics.

Have you put in the same effort as others around you, but aren’t seeing the results you want? This article is specifically for you.

First, we’ll give you answers. We’re going to do a deep dive into the many ways genetics can affect your chest muscles.

However, we won’t leave you hanging there. We also cover the best exercises and tips to work with – and perhaps overcome – the chest genetics you’ve been dealt.

What are bad chest genetics?

bad chest genetics

Bad chest genetics are one or more factors that make it difficult or impossible for some individuals to get an idealized, aesthetic chest.

These traits include things like body type, muscle fiber type distribution, hormone levels, and even age and gender.

More specifically, bad chest muscle genetics affects muscle attachment sites and the level of separation between the heads of the muscle.

It also affects the fusion of the pectoralis major with the front part of the deltoid and the crossing of the muscle fibers at the sternum.

In short, Mother Nature has a big say in your potential for the look and performance of your chest muscles.

The following sections will dive further into these genetic factors before telling you how to work with what you’ve got.

Different Types of Muscle Fibers in Your Chest

One genetic factor that can influence the look of your chest is the proportion of fast or slow-twitch muscle fibers you have.

Our muscle tissue has different types of fibers, called type I, type IIA, and type IIB. 

Type I, or slow-twitch muscle fibers, are used in more endurance-based, aerobic activities.

Type II fibers are used for shorter durations but are thicker in diameter.

The proportions of these fiber types vary from muscle to muscle and person to person.

This means that someone with a genetically higher proportion of type II fibers in the pectoral muscles will have an easier time growing a bigger chest.

Reasons You Have a Gap Between Your Chest Muscles


As mentioned, genetics plays a big role in how your chest muscles look.

In terms of having ‘bad’ inner chest genetics, the origin of the pectoralis major muscles can attach to the sternum further apart from each other, leaving a gap.

Many other variations of chest genetics exist, from attachment of the muscle to different ribs to the existence of entirely new pec muscles in between the pec major and minor.

For example, if you look at a photo of Terry Crews, you can see he has a wider gap in the upper chest area.

Popular fitness influencer and bodybuilder Tristan Lee has somewhat bad muscle genetics in the lower chest, with a wider gap between attachment sites.


While bad chest muscle genetics are certainly a factor for some people, others may simply lack the muscle mass for a good-looking chest.

The most prominent cases of bad chest genetics are when the individual is either very muscular, very lean, or both.

For everyone else, you may simply need to keep training to build the chest up.

If you’re a beginner, chances are genetics isn’t the primary factor in your underdeveloped chest muscles.

And remember – you can’t change genetics. Work with what you have and keep a consistent training regime to see longer-term chest gains.


As mentioned above, a gap between the chest muscles becomes more apparent the leaner you are.

For those who aren’t necessarily looking to compete at super-low levels of body fat, adding some weight can help create a fuller-looking chest.

Since the gap is created by shorter muscle attachment sites, a little extra body fat can actually create a less harsh appearance to the middle chest.

Examples of how this can work can be seen in many progress videos of skinny teens who train and bulk for several years.

They often start with next to no muscle, and the chest can look as though they have bad chest genetics, with visible ribs or prominence in the breastplate.

After a few years of consistent training and good nutrition, however, the chest gaps – along with everything else – fill out and the appearance improves markedly.

Chest Genetics Types

Related: Why Are My Arms So Skinny?

There are obviously many factors that go into having good vs. bad chest genetics.

This section will briefly cover what it means to have “good” chest genetics (in terms of aesthetics and strength).

We’ll also cover what typical “bad” muscle genetics can look like.

For those who are disappointed with a slight chest gap, it’s also important to include some information about the real worst chest genetics conditions.

Good Chest Genetics

A lot of people would agree that one of the best examples of good chest genetics is Arnold Schwarzenegger.

You can see in the footage above the combination of perfect muscle insertions along the entire origin of the muscle, along with huge mass and definition.

The result is a barrel-like chest. There’s great separation between the lower and upper heads and aesthetic blending into the deltoid muscles.

Of course, Arnold had help from performance-enhancing substances. But genetics (and a lot of insanely hard work) played a big role in Arnold having arguably the best chest of all time.

Bad Chest Genetics

When it comes to the general fitness community, “bad” chest genetics are seen as non-optimal tendon insertions on the sternum and ribs, creating gaps in the muscle area. 

Even genetic traits such as nipple size, shape, and location can change the aesthetics of the chest.

Another condition in this area that can affect the look of the chest is gynaecomastia, which involves excessive breast tissue growth in males.

But there are more severe genetic traits that can have consequences beyond looking good on stage or in the mirror.

These traits can result in deformities of the thoracic wall and can require surgical intervention to remedy.

Examples include conditions like pectus excavatum, with a pronounced ‘caving in’ of the chest wall.

This can be associated with breathing difficulties, pain, and even the risk of cardiovascular problems.

Another condition you may come across is pectus carinatum, known as “keel chest” or “pigeon breast.” This involves abnormalities in the chest cartilage, causing a protrusion from the sternum.

Rare genetic mutations can result in other chest wall problems, such as split sternums or shortened ribs.

While genetics can be a problem for sure, try to keep it in perspective in cases where it’s only an aesthetic issue.

How to Know if You Have Bad Chest Genetics

Bad chest genetics can present in different ways, depending on the individual. 

First, examine your general body type. Record features such as limb lengths, muscle characteristics, and fat tissue around the chest area.

Flex your chest in a mirror. Can you see the origin points along the centerline? Are there disparities in muscle mass between the lower and upper chest?

Another way chest genetics can impair your results is in your training.

Having a relatively flat chest wall can make certain pressing exercises less mechanically advantageous. This means that other muscles like the deltoids do the bulk of the work.

You’ll have to experiment with the exercises and tips below to see which exercises give you the best results for your build.

How to Fix Bad Chest Genetics

Related: Top 10 Exercises & A Full Dumbbell Chest Workout Without Bench

Once you’ve assessed your chest muscle genetics, it’s time to do two things.

First, list the things you can change. Then, list the things you can’t.

For example, the shape of your ribcage or the attachment points of your pecs can’t be changed without surgical intervention.

While this is an option for some people, it obviously comes with many inherent risks. Weigh the options carefully before going down this route.

On the other hand, there are many things you can do to build an impressive chest, even with “bad” chest genetics.

In fact, 99% of people reading this can probably do a lot of things to improve chest mass and definition.

The Best Chest Exercises to Fix Bad Chest Genetics

Related: Chest And Shoulder Workout

Best exercises to fix bad muscle genetics

The following exercise categories are the fundamentals of chest training. They cover all of the movement patterns necessary for creating an impressive chest.

While they may seem familiar at first, the focus of this article is how to tweak these movements for your chest.

There may be a tweak in equipment or technique here that can change an exercise from being ineffective to a total game-changer.

There are three foundational movement patterns here, but the variations possible means there are dozens of exercises available for you to work with.

1. Bench Press

While seen by many as the number one strength builder for the chest, the bench press has its critics compared to other chest exercises.

One of the issues with bench press for those with bad chest genetics is that the shoulders and triceps can take over the brunt of the work, underutilizing the pecs.

But this can be fixed with things like hand placement, elbow position, shoulder blade posture, or by using dumbbells or machine variations.

You can also play with the level of incline, for those who need to focus on their bad upper chest genetics.

At the end of the day, a bench pressing movement – tailored to the individual – is going to be key for building a solid foundation of strength for the chest.

Equipment requirements: Bench, barbell, plates, rack, dumbbells, machine

How to perform the bench press: 

  • Lie on the bench with the bar over eye level
  • Grab the bar at the optimal width for your limb length
  • Squeeze the shoulder blades together and arch the back slightly
  • Unrack the bar and hold the arms locked out over the nipple line
  • Keep the elbows slightly below shoulder level as you control the bar to the chest
  • Pause briefly before pushing the bar to the starting position

Benefits: Foundational chest strength builder, allows muscle growth by intensity, functional

Pro tips: Focus on the chest muscle action of bringing the elbows toward each other in the center to get the most pec activation.

2. Chest Fly

Next, we need to isolate the pec muscles from the delts and tris with chest fly movement.

Try this with a butterfly machine, cable setup, or dumbbells on a bench to see what gives you the best chest connection.

The fly has the advantage over the bench of allowing a greater total range of motion for the pec major. This gives a greater stretch at the bottom, as well as more adduction at the top.

Again, for those with bad upper chest genetics, an incline bench or low cable setup can be used to emphasize the clavicular head of the pec muscle.

Equipment requirements: Butterfly machine, pec dec, cable machine, or bench and dumbbells

How to perform a chest fly: 

  • Sit or stand holding the handles or weights out to either side of the chest
  • Pull the shoulders back and down, and brace the core
  • Squeeze the chest to pull the hands toward each other in the center
  • Contract the pecs harder to push the elbows toward each other
  • Slowly control the handles back until a good stretch is felt in the chest

Benefits: Chest isolation movement, good range of motion, solid pec contraction

Pro tips: Use advanced training techniques like partial reps or slow negatives to further fatigue the chest muscles.

3. Single-Arm Cable Crossover

Finally, we have a single-arm chest exercise which adds a couple of final pieces to the puzzle.

Single-arm crossover variations are great for correcting imbalances, which can be common for those with bad chest genetics.

They also allow you to horizontally adduct the shoulder past the midline of the chest. This creates a massive stimulus for the muscle.

Single-arm crossovers can be done from a range of angles. This allows you to focus on the lower, mid, or upper sections of the pecs.

This exercise is also where you can work on building a better connection with the pec major, which we’ll discuss in more detail shortly.

Equipment requirements: Cable machine, handle

How to perform the cable crossover: 

  • Stand side-on to the cable machine, holding the handle at the desired height
  • Keeping the midsection tight, scoop the handle across the midline of the body
  • Contract the pecs hard and hold the end position briefly
  • Slowly fight the handle back to the starting position

Benefits: Corrects any imbalances between pec muscles, allows greater ROM at end range

Pro tips: Experiment with slight torso rotations and adjustments on hand position to see what gives you the best chest contraction.

Pro Tips to Fix Bad Chest Genetics Faster

Tips for getting good chest genetics

With the exercise catalog covered, it’s time to go over the essential tips you’ll need to sculpt an impressive chest.

Each of these tips in isolation can help improve your chest growth. In combination, they can be a powerful force against even the worst chest genetics.

More Mobility Work

If you think you have bad chest genetics, what you do before and after your workout becomes even more important.

Flattened chest wall shape or shortened muscle lengths mean that you’ll have to focus even more on creating as much flexibility and movement in the chest as possible.

Make sure you dedicate time to stretching, soft tissue work, and posture correction drills. This will ensure your chest has the maximal chance to move under load.

Connect With Your Pecs

Mind-muscle connection is critical for those fighting genetics, as this can help counteract biomechanical disadvantages.

Use the exercises above like the fly and crossover to ensure you feel your pecs contracting in the right way throughout the movement.

You can also gauge from post-workout soreness which muscles are taking the bulk of the work, and adjust accordingly.

Progress Training Parameters

Like with any training program, it helps to steadily progress in your training.

Whether it’s more volume, frequency, or intensity, find ways to slowly but surely increase the demand on your chest to grow bigger and stronger.

Your chest won’t grow simply because you want it to. You have to provide the mechanical and metabolic stimulus to force it to adapt.

Start Bulking

As mentioned, chest genetics are particularly visible on extremely lean individuals, whether they have large muscle mass or not.

To take the Terry Crews example from earlier. No one would complain about having that man’s physique.

However, for those who are bothered by the look of bad chest genetics, one solution is to bulk to a slightly higher body fat percentage.

While we’re not talking getting to overweight levels, having slightly more body fat will soften the look of the chest. This will fill it out for a rounder, smoother look.

Bulking this way will also help add more muscle mass and improve strength levels as you consume slightly higher calories and protein.

Identify Target Areas

Once you’ve built a solid foundation of muscle on the chest, you can further tweak the shape and definition of the muscle.

For instance, if you find that your upper chest is lacking, opt for more incline movements.

If you suffer from bad inner chest genetics, the fly and single-arm crossover variations above will be your best friend in building a bigger mid chest.

For more info, check out this article on building a massive inner chest.

Program these specific exercises into your chest workout to build a complete, full-looking chest.

Frequently asked questions

Related: Powerlifting Program

Can I fix bad chest genetics?

Genetics is definitely something that you can work around.

In extreme cases, surgical intervention may be required, although that’s dependent on consultation with a medical professional.

For cases of bad chest genetics just with muscle insertions around the sternum, just work on the exercises and tips above to build your chest as best you can.

How do I know if my chest genetics are bad?

The methods in this article can be used to assess your chest muscle genetics and see where your starting point is.

It’s important to note here that “bad” is mostly a relative term when talking about aesthetics.

Sure, genetic elements can play a role in competitive bodybuilding. But for the general fitness population, it’s not something to worry about.

Unless you’re an advanced lifter with significant muscle mass and shredded body fat levels, chances are, there’s a lot you can do to improve your chest.

How do you grow a chest with bad genetics?

Those with “bad” chest genetics grow their chest the same way as everyone else.

Focus on progressing your strength and size with the exercises listed above and tweak your program to work on specific target areas.

The right combination of training, nutrition, recovery, and consistency will result in improvements to your chest, regardless of small genetic variations.

Is a big chest genetic?

As with the example of Arnold split, genetics do play a role in your potential for muscle growth and aesthetics.

That being said, genetics alone will do next to nothing to give you a big chest.

If Arnold sat on the couch and ate junk, he wouldn’t have the god-like chest we still admire today.

Genetics simply gives you a platform to work from. Anyone who puts the work in can achieve impressive results from there.

Final Thoughts

What do you think of our tips for working around bad chest genetics?

From an aesthetic point of view, “bad” chest genetics aren’t as big of a problem as you might think. Plenty of pros have those traits and know how to work with, as well as around, them.

In many cases, you just need to make small adjustments to exercises you may already be doing. In others, you might simply want to bump up your body fat a little. 

Let us know if you struggle with chest genetics – and which tips you plan to try – in the comments.

If you have a friend or training buddy who is struggling to build an aesthetic chest, be sure to share these tips with them, too.