Why is My Non-Dominant Pec Bigger? (Here’s 6 Reasons Why)

You might have never thought you’d ask this, “Why is my non-dominant pec larger?”

However, it appears the struggle is real.

There are various online forums and Q&A sites inundated with this very question.

At first, it seems just plain weird.

I mean, if one of your pecs is going to be bigger you’d expect to be on your stronger side, right?

But, the way you’re training can actually have the opposite effect.

Allow me to explain why.

Why is My Non-Dominant Pec Bigger?

As strange as it seems, there are various reasons why your non dominant pec is bigger. Firstly, you may be putting in more effort with your weaker side, whether this is pressing a barbell or dumbbell harder, or squeezing the bar tighter. This will usually mean that you are contracting your non-dominant side harder, which may lead to a greater size increase. Furthermore, as you’re putting more effort into ensuring your weaker side can “keep up” you may be adhering to stricter form on that side, e.g. fully retracting the shoulder blades.

1. You’re “Pressing” Harder With Your Non-Dominant Side

Firstly, I should say that “bigger” doesn’t always equate to “stronger”.

So, if you’re finding that your non-dominant pec is larger, but yet weaker, this is perfectly feasible.

One reason that you may notice this difference in size is because you’re working your weaker side harder.

By this I mean that you are aware that there is a strength difference, so you tend to focus on using your weaker side more forcibly.

Let’s take the barbell bench press as an example.

You typically find that as you lower the barbell you can feel it more on your non-dominant side.

The same can be said when you press the barbell back up.

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Suddenly, all your efforts are concentrated on your weaker side.

In effect, you are using the mind-muscle connection on your weaker side, while your stronger side is left to its own devices.

Basically, your stronger side doesn’t need your focus or attention, as it is more than capable of dealing with the weight.

2. You’re Squeezing Harder With Your Non-Dominant Hand

Staying with the example of the bench press for a moment, it’s also likely that you’re squeezing harder on the bar with your non-dominant hand.

This once more is down to you trying to exert more effort on your “weaker” side.

Basically, you’re worried about your weaker side letting you down.

So, there is a tendency to squeeze the bar tighter in order to ensure that your non-dominant side is playing its part.

This will immediately contract the pec on that side harder.

In effect, that side on your body, from your hand, to your arm, to your shoulder, and to your pec is going through an isometric contraction.

And you are holding this contraction throughout your entire set.

When you repeat this process over-and-over again on a regular basis it will have an impact on muscle growth.

Hence, your non-dominant pec ends up bigger.

3. Are You Adhering to Strict Form (Even With Dumbbells)?

I have alluded to this already, as in your concentration is almost solely focused on your weaker side.

However, when it comes to training chest, I often see the setup seems to differ on each side.

One of the main things that you should be doing prior to bench pressing is retracting your shoulder blades.

This helps to activate the antagonistic muscles, the lats, and will ensure that your bench doesn’t become solely a front delt exercise.

However, I have noticed trainees who seem to execute scapular retraction perfectly on one side and not the other.

Not only will this impact on the exercise, potential muscle and strength gains, but it could also be a catalyst for injury.

The exact same can be said when using dumbbells.

You’ll often hear people say that if you want to even out muscle imbalances then you focus more on dumbbell training.

Now, while this may be true to some extent, you can still commit form errors with one arm and not the other.

In the case of dumbbells, you could even be lowering one side further, and therefore using more effort to press the dumbbell back up again.

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You could even say the same for an exercise like cable flyes.

So, ensure that you maintain strict form on both sides at all times.

The Official Bench Press Checklist (Avoid Mistakes)

4. Are You Fairly New to Training?

So far I’ve covered the basics on why a size imbalance may occur.

However, having one side bigger than the other happens quite often if you’re fairly new to training.

Basically, in your everyday life you will typically use your stronger side to do most things.

Whether this is pushing a door open, lifting something up off the floor, and even lifting yourself out of bed.

In effect, your more dominant side is already being stimulated on a regular basis.

So, when you first start training you may notice that your weaker side seems to come on in leaps and bounds, whereas your stronger side can lag behind.

This is also why most gym newcomers see some amazing gains in their first few months, and then things seem to slow down after this.

I’m willing to bet that most people who are new to the gym make a beeline for the bench press area straight away.

It’s just the done thing, we all want to test our strength by benching.

So, your non-dominant pec is literally being exercised for the first time ever, and will therefore make faster gains.

I wouldn’t overly worry about this, as with time things will even out.

5. No-One is 100% Symmetrical

I think it’s important to say that no-one is 100% symmetrical.

This is even true of professional bodybuilders whose main aim is to produce perfect symmetry of the muscles.

Even the great Arnold Schwarzenegger had one bicep slightly bigger than the other.

So, it’s perfectly normal not to be completely even.

As I’ve already mentioned, you may generally be working harder on your non-dominant side.

You must also remember that outside of the gym you tend to favor one side more than the other in just about everything you do.

Therefore, you can put all your time and effort into trying to achieve that perfectly symmetrical look, but you’re likely to be the only one who’s ever achieved it.

6. Are You Overthinking This?

This leads on nicely from what I’ve just said.

No-one is as big a critic of our own body as ourselves.

Plus, no-one studies our body in as much detail as we do.

So, you could be agonising over a slight imperfection that is hardly noticeable to anyone else.

You should also remember that we never look at our own chest from the front with our own eyes.

You will always be evaluating yourself through a mirror.

So, you have to take into consideration whether you’re standing completely straight, whether it’s a trick of the light, and also that this is simply a reflection.

Plus, the more you stare at your pecs, the worse it becomes.

My advice is not to overthink this.

In fact, you’re probably making it worse than it actually is.

Additionally, you are likely noticing it more because your overall chest isn’t as well-developed as you hope.

You can check out the video below from Scott Herman where he discusses both a small and uneven chest.

Scott also includes a workout to help you fix this problem.

“My Chest is Small & Uneven” – This is Why (Workout Included)

Final Thoughts

I hope you have a better idea of why your non-dominant pec is bigger.

This usually occurs because you end up putting in more effort with your “weaker side”

Whether this is pressing harder, squeezing harder, or adhering to better form with your non-dominant side.

You may also notice a certain unevenness if you’re new to training, as your weaker side is reacting better to the stimulation.

Finally, it’s important to remember that we all tend to have slight inconsistencies with our body, so there’s no reason to overthink this.

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