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Built By Science: Chest

Fill out your shirt with a bigger, stronger, more powerful chest. Here's how science can help you grow!

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A lot of guys go to the gym to build a big, thick chest. It's not uncommon to see a novice hit the gym and knock out 20, 30, or 40 sets of bench press in one workout. Doing that many sets of bench in one workout can spell bad news for your shoulders, but it also neglects the many other effective chest exercises available.

I'm going to teach you how to train your chest more effectively, how to target specific chest muscles, and how to get the most from your hard work in the gym. It's time to harness the power of science and apply it to your best body.

Built By Science Chest
Watch the video: 14:22

Muscular Anatomy

To better target and more effectively train your chest, it's important to understand how the muscles are put together. Here's what you need to know about the muscles in your chest.

Pectoralis Major

This is the one you're probably most interested in training. Your pec major, which is your biggest chest muscle, actually has three sub-heads: the clavicular head, the sternal head, and the abdominal head. These heads are important to know because they can be specifically trained through particular movements.

Clavicular head

The clavicular head is the upper part of your pectoralis major. It runs from your clavicle—your collarbone—down and across the top part of your chest. It attaches to your humerus, or upper arm. Most guys struggle to build the top portion of their chest, so we'll pay special attention to this area.

Sternal Head

The sternal head is quite a bit larger than the clavicular head. It runs from your sternum, comes across your chest, and inserts at your humerus.

Abdominal Head

The abdominal head runs from your rectus sheath, which is a big piece of connective tissue that surrounds your abdominal muscles, continues up and across the bottom portion of your chest, and attaches to your humerus.

Pectoralis Minor

Your pec minor lies beneath the pec major. It's a really small muscle group that you're probably not going to spend too much time trying to develop.

The pec minor runs from a little boney prominence at the top of your scapula (called the coracoid process) and attaches to ribs three, four, and five. I want you to know that it's there, but you don't need to worry about it too much. It's mostly there to help you breathe.

Serratus Anterior

The serratus anterior starts from the inside of your shoulder blade, wraps around your side, and attaches onto the front of your ribcage. Really lean bodybuilders have great looking serratus muscles.

Although it's another muscle you probably won't spend a lot of time developing, it's crucial for a balanced physique and healthy shoulders.

Dumbbell Pullover
Dumbbell Pullover

Skeletal Anatomy

Your bones and joints play a critical role in how your chest works and how you train it. You can't train your chest without also thinking about your shoulders, back, and elbows.


Your scapula is an important part of your pressing movements. When you set up on a bench press, you want to pin the shoulders down and back to create a stable base from which to press. It might be on the posterior side of your body, but your scapula is definitely going to come into play during chest training.

Shoulder Joint

The scapula and humerus come together to form the glenohumeral joint. This joint is essential to chest training. It's also the most prone to injury. If you don't set up well for your presses, you could do some serious damage to your shoulders.


A lot of people don't think about this, but every time you do a pressing exercise, you extend your elbow. Your elbows have to function smoothly and pain-free for your chest training to be at its best.

Muscular Function

Let's put all the pieces together and see how your muscles and bones work together in real-world, functional movements that you do every day.

Pectoralis Major

All three heads of your pec major work together to create internal rotation. If you put your arm out to the side and rotate it down and forward, you're rotating your arm internally. Your arm can't do that without the help of your pecs.

A lot of us aren't too worried about how functionally our chest can rotate our arm. Instead, we want to see striations and learn how to get big and lean. One of the best exercises to do this is the incline flye. This movement is called horizontal adduction—you pull across your body.

As you do the movement, those pec fibers elongate and then shorten and get tight. All the heads must work together to perform horizontal adduction.

Clavicular Head

Your clavicular head is responsible for shoulder flexion, or raising your arm over your head. Incline presses, when your arms go overhead, are going to hit that top portion of your chest.

Sternal and Abdominal Heads

To best hit the bottom portion of your chest, decline presses and dumbbell pull-overs are best. Your torso position and the position of your shoulders make a huge difference in which portion of your chest you train.

Serratus Anterior

Your serratus anterior is most noticeable when you do something which protracts your shoulder. When you reach forward like you're doing a row, you protract your shoulder. The top part of a push-up really works the serratus anterior. Push-ups may not make your chest massive, but they definitely train that serratus.

The serratus is also one of three muscles which allow your shoulder blade to rotate upward so you can put your arms over your head. Your serratus, lower traps, and upper traps work together to create upward rotation. Visible serratus muscles look cool, but their function is critically important to your shoulder health.

Key Exercises

These are the movements you'll see throughout Built by Science. They're some of the best options for developing a strong, powerful chest.

EXERCISE 1 Dumbbell Incline Bench

Dumbbell Incline Bench
Dumbbell Incline Bench

Keep your legs and abs tight for this exercise. As you move the dumbbells overhead, tuck your elbows down and in. Flared elbows put a lot of stress and torque on your shoulders.

Although you use all three heads of your pec major for this movement, putting your arms overhead will especially tax your clavicular head. If you're having trouble filling out the top part of your chest, make sure you add the incline bench or flye to your program.

If this movement bothers your shoulders, move to a neutral grip with your palms facing each other. Having your hands this way will give your shoulders a little more breathing room and should make you feel better.

EXERCISE 2 Dumbbell Flye

Dumbbell Flye
Dumbbell Flye

To hit the pecs and get that great horizontal adduction, dumbbell flyes are the way to go. Get a stable base: abs tight, back tight, and legs tight. Keep your elbows soft and stretch through your pecs.

As you bring your hands together, those fibers will pull together and shorten. This movement hits all three of your pec major heads evenly.

EXERCISE 3 Push-up


I know, you've probably been doing push-ups for years and haven't noticed how they've trained your chest. I want to give you a few subtle cues to and tricks to make your push-ups more effective.

This total-body lift connects your upper and lower body. Keep your abs tight, tuck your elbows on the way down and then, to hit the serratus, exaggerate trying to push your body as far away from the floor as possible. The upward squeeze will engage the serratus at the top of the push-up.

Better Chest, Built By Science

A good understanding of how the bones, joints, and muscles work together will help you build a program to develop unbelievable pecs. Mixing up your movements, adding incline and decline presses to your regular flat bench program, and swapping barbells for dumbbells influence how your muscles work. The better you understand this, the better your physique is going to look.

Follow the Built By Science Program

Look for the exercises and techniques discussed above in the weekly chest workouts of the six-week Built by Science program. Watch all the overview videos before attacking the gym. Remember, you need to combine mind and muscle to build your best possible body.

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