If you've been in the iron game for more than a day, you know it takes more than curls to build big arms. Believe it or not, the triceps make up the majority of your arm mass above the elbow, so if you want bigger arms, it's triceps—not biceps—that need to be the priority.
There are three heads to the triceps—hence the "tri" in the name. The long head of the triceps is the one you see when you flex the back of your arm. The lateral head is the one directly behind it that helps complete the horseshoe shape. Then there's the medial head, which is the most difficult one to see because it sits underneath the other two.
All three heads must be trained to develop size and strength in the upper arm. While it's basically impossible to work one head without the other two helping out, you can make sure one head does the majority of the work using exercises that specifically target each head. This workout aims to do just that.
Each of the three exercises in this workout places emphasis on a different head of the triceps, allowing you to properly train and build up your upper arm the way you've always wanted.
Reverse-grip single-arm push-down
A reverse-grip exercise allows you to focus on the medial head of the triceps. You want to make sure to maintain as much tension as possible so this head does more work. For constant tension, cable movements work best, and starting with a single-arm movement helps you focus on each arm individually. This exercise also helps warm up your elbows for the rest of the workout.
If you are new to reverse grip extensions, or it's been awhile, go light with the weight until you're confident with your form. Even if you are comfortable with this exercise, there's no need to go super heavy—choose a weight that challenges you at about 12 reps. Keep your rest periods short. After all, one arm is already resting while the other is working.
Neutral-grip lying triceps extension
Using a neutral grip places more emphasis on the lateral head of the triceps. Doing these extensions lying down helps you isolate the muscle more than if you were standing, which is always better for targeting specific areas of the muscle. You can do this with dumbbells or a triceps bar with vertical handles. If your gym has a triceps bar, I'd give that the nod over dumbbells.
To execute the movement correctly, lower the weight behind your head so you can maximize the stretch at the bottom of the movement. When you press the weight up, lift it away at an angle like you want to touch the top of the wall behind you. This will keep pressure off the shoulders and more where you want it—on the triceps. Add weight with each set and rest 45 seconds in between.
Kneeling rope cable press-down
Now that you've targeted the other two heads of the triceps, shift your focus to the long head, the most visible part of the triceps. To maximize the contraction of this muscle, you'll need to be able to flex your wrists and separate your arms. This is why the rope attachment is really the only choice for this exercise. Use the longest rope attachment you can find so you can extend your range of motion.
Doing cable press-downs while kneeling minimizes momentum, keeping the work in the triceps. Because of this, your form and control will have to be tighter than if you were standing. At the bottom of the movement, separate the rope as you extend through the elbows and squeeze your triceps as hard as you can.
Let the rope back up slowly before starting the next rep. You might be tempted to cheat by speeding up the reps, but don't. Extra time under tension is crucial to building mass, and slow and controlled reps will help you more in the long run.