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Built By Science: Arms

Killer arms make a good physique great. Look under the hood of your biceps and triceps and learn the best exercises for maximum muscle growth.

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Chances are, the very first time you stepped in a gym, you went straight through an arms workout. Guys and girls alike want a killer set of arms because they're one of the most impressive and visible muscle groups on your body. There's a reason you can't walk into a gym without seeing at least one person doing biceps curls.

You might want great arms, but you might not be getting the most from your arms training. It's time to train your biceps and triceps harder and smarter. I'm going to teach you how little things like muscular attachment points, different grips, and specific positions can make a profound difference on your results.

Built By Science Arms
Watch the video: 17:57

Muscular Anatomy

To train your arms effectively and efficiently, you need to understand how they're put together. Here's what you need to know about the muscles in your arms.

Anterior Arms

To train the front of your arms and build a set of baseball biceps, you need to focus on three specific muscles: the biceps brachii, the brachialis, and the brachioradialis. The differences in these muscles are important to note.

Biceps Brachii

Biceps means "two heads." You have two heads to your biceps muscles: the short head, which originates at the front of your scapula and inserts at top of the radius (the forearm bone that ends near your thumb) and the long head, which also originates at the scapula but takes a longer route to insert on your radius.


The brachialis runs from the midpoint of your humerus, your upper-arm bone, to your ulna (the forearm bone that ends near your pinky finger). Because the brachialis does not insert on the radius, it does not help pronate or supinate your arm. The main role of the brachialis is to help flex the elbow joint.


Your brachioradialis is a long forearm muscle. It originates on the humerus and attaches at the end of the radial bone.

baseball biceps
Build your set of baseball biceps, by focusing on three specific muscles: the biceps brachii, the brachialis, and the brachioradialis.

Posterior Arms

Most people are focused on their biceps because they pop in the mirror, but your triceps brachii are arguably up to 75 percent of your upper arm, so it's important to give them just as much attention. Triceps means "three heads." To get that horseshoe shape, you need to hammer each head of your triceps.

Lateral Head

The lateral head of your triceps originates on the upper humerus and attaches at your elbow, or what's known as the olecranon process.

Medial Head

The medial head starts on the back side of the humerus and attaches to your elbow.

Long Head

The long head is a little different from the other triceps heads. The long head runs from your scapula and attaches at your elbow. Because it attaches on the scapula, you can move the arm and shoulder to isolate it, which I'll discuss in more detail below.

Skeletal Anatomy

Bones and joints play a critical role in how your arms are able to move. Understanding how your bones and joints work will help you tweak exercises and target specific muscles.

Anterior Arms

Two key joints influence your biceps training. The position of these joints can alter which muscles are being trained.

Shoulder Joint

The shoulder joint, also called the glenohumeral joint, is important to training your arms because the long head of your biceps brachii crosses it.

Elbow Joint

The elbow joint, or what's called your radialulnar joint, is important because the rotation of your arm impacts which muscle you target. Moreover, to train your biceps, you must flex your elbow joint.

Posterior Arms

The same joints and bones are important to your triceps training, but for different reasons.

Shoulder Joint

The shoulder joint is important in training your triceps because of your triceps long head. To isolate the long head, you have to elevate your arm overhead.

Elbow Joint

Elbow extension, or the straightening of the elbow joint, is relevant to almost every single triceps move. Push-downs, kick-backs, and compound exercises like the close-grip bench press all require elbow extension.

Muscle Function

Up to this point, we've covered muscles, bones, and joints involved in arm training. Let's take it a step further and look at how all of those aspects work together to move your body. As you begin to understand different shoulder and elbow positions, you'll learn how to maximize your arm growth and you'll get more out of your arms training.

Anterior Arms

Supinated Grip

The biceps brachii are important because they help create flexion and supination. To hit your biceps most effectively, use a supinated grip.

Neutral Grip

As soon as you go into a neutral grip, like a hammer curl, you have a direct line of pull and will maximize development of brachialis.

Pronated Grip

If you go into a fully pronated grip, you lose the mechanical advantage of your biceps. That's important because, in this position, you have a direct line of pull to your brachioradialis. So when you're doing a reverse curl, you're really going to isolate the brachioradialis.

Pronated Grip
Supinated,Neutral, and pronated Grip

Posterior Arms

Elbow Extension

When you go from a flexed to an extended elbow position, you're working all three heads of the triceps equally.

Overhead Elbow Extension

As soon as you move the weight over your head, you start to preferentially recruit the long head of your triceps.

Key Exercises

This is where the rubber hits the road. These are the key exercises you'll need to carve a solid set of arms. The video might make look these exercises look easy, but it's important to note that the intensity of your training matters. You have to crank it up if you want to maximize your arm development.

Anterior Arms

Add these biceps-enhancing movements to your training arsenal.

EXERCISE 1 EZ-Bar Biceps Curl

I like using the EZ-bar better than a barbell because it's slightly more forgiving. Many people aren't quite symmetrical between their elbows and between their shoulders. A barbell tethers your shoulders together and can give those people issues. EZ-bars are easier to use and more shoulder and elbow friendly.

ez-bar curl

To get the most out of your EZ-bar curl, keep your abs and glutes tight. Those contracted muscles will help you move more weight and will protect your lower back. Fully extend at the bottom of the movement and squeeze at the top. Use a supinated grip to work those biceps hard.

EXERCISE 2 Reverse-Grip EZ-bar Preacher Curl

For this movement, we'll use a pronated grip so the biceps are inefficient and we work the brachioradialis. Keep your elbows pinned to the pad and a neutral alignment in your wrist. Contract at the peak of the movement and be sure to get a full extension. We're looking for a full range of motion.

This exercise offers more isolation than a barbell curl, so you won't be able to lift as much weight as you would doing a regular EZ-bar curl. Put this movement at the end of your workout—it's icing on your training cake.

This move is great for forearm development. Rather than using grip-specialization exercises, this exercise works your upper and lower arms in one movement.

EXERCISE 3 Seated Hammer Curl

seated hammer curl

This movement will help you hit the brachialis. Keep your hands in a neutral grip, with your palms facing each other. If you want to tweak this lift, add a little supinated twist at the top to recruit your biceps brachii. Keep your abs tight to protect your back and prevent yourself from cheating.

Posterior Arms

Don't leave your triceps hanging! Add these movements to hit all three heads of your triceps with intensity and efficiency.

EXERCISE 1 Close-Grip Bench Press

In my opinion, there's no better movement for triceps training than the close-grip bench press. Some of you might think that, because we're dealing with a bench press, this is a chest exercise. That's true, but you're still getting a ton of elbow extension, which is going to help build big triceps.

Take a shoulder-width grip on the bar. If you get too narrow, you'll put too much strain and torque on your wrist at the bottom. Turn your knuckles up for neutral wrist alignment. Pull the bar down to your chest while keeping your elbows close and tight to your body. Finish with your knuckles up.

A lot of people think that doing arm exercises means isolated, single-joint movements. But this big, compound movement allows you to overload your muscles. You'll get help from your chest, and those big joints help you push serious weight to develop larger and stronger muscles.

EXERCISE 2 Dumbbell Overhead Triceps Extension

Putting your arms over your head isolates the long head of the triceps. This is a simple movement but remember to keep the abs tight and concentrate on stretching into a full range of motion. Your elbows should stay up.

Dumbbell Overhead Triceps Extension
Dumbbell Overhead Triceps Extension

Better Arms, Built By Science

Building great arms is more than just a combination of isolation exercises at the end of a workout. If you want good arms, push yourself when you hit your compound movements.

Don't forget, you build your arms virtually all day. Your biceps and triceps are used on movements like the pull-up and the bench press. Those back, chest, and shoulder days will indirectly help develop your arms.

The addition of an arms-isolation day that includes the above exercises will help supercharge your arms development.

Follow the Built By Science Program

Look for the exercises and techniques discussed above in the weekly arms 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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