Want Bigger Arms? Start Doing Dumbbell Skull Crushers

When you think of big arms, you picture peaked biceps—but your triceps make up two-thirds of your upper arm size and are key players in compound pushing exercises. But you can’t only rely on shoulder presses and push-ups to grow and strengthen your tris. To build them up, you need to isolate them, and few moves do it better than the dumbbell skull crusher.

I interviewed Adam Salvatore, a CSCS and TPI Level 1 trainer who works with golf athletes at Rotational Power Strength golf gym, to go over common mistakes, programming tips, and variations of the dumbbell skull crusher. 

What is a Dumbbell Skull Crusher?

The dumbbell skull crusher is an isolation exercise, meaning it targets one muscle. In this case, it targets your triceps, the muscle located on the back of your arm that extends your arm at the elbow joint. It’s easy to do, too. Just lie face-up on a weight bench, hold two dumbbells straight over your chest, and lower them behind your head. 

This exercise is brutally effective for two reasons: First, it loads the muscle in a stretched position, which recent research shows may be more effective for eliciting muscle growth. Second, the triceps play a key role in the top portion of most pressing exercises; stronger triceps will directly impact those exercises, too. 

How to Do Dumbbell Skull Crushers

1. Grab a dumbbell in each hand, and lie back onto a weight bench, like you’re doing a dumbbell bench press. Plant your feet firmly on the floor, slightly arch your lower back, and extend both dumbbells directly over your chest, palms facing each other. 

2. Bend your elbows to lower the dumbbells toward your shoulders, keeping your elbows tucked in and pointing straight ahead.

3. When you finish lowering, extend your elbows to lift the dumbbells back up. Make sure the weights stay directly overhead and are not leaning forward or back behind your shoulders.

4. Repeat for desired number of reps.

Programming Tips: How to Add Skull Crushers to Your Routine

Here are some suggestions on incorporating the dumbbell skull crusher into your skull crushers workout:

Do Them Later in Your Workout

Your triceps are key players in other compound exercises, like the bench press and dumbbell shoulder press. Fatigued chest muscles won’t interfere with your skull crushers, but tired triceps will make it harder to bench. Generally, you should do big, multi-joint lifts earlier in your workout and save the single-joint exercise for the end.

Stick With Higher Reps

Lifting dumbbells does not feel as stable as lifting a barbell, so don’t try to push heavy weights for low reps. Exercise scientists have found that you can build muscle with a wide rep range of six to 20+ reps. There’s no need to risk your joints with this movement. Go lighter and push your sets. 

“Part of a well-designed training program will include periods of higher volume and reps where the lifter will attempt to put on muscle mass, and more muscle support stronger lifts,” says Salvatore. But remember that what ultimately matters is your time in the game—consistency will get you both big and strong.”

Go to Failure

Pushing to failure ensures you’ve eeked out every ounce of muscle-building potential from your muscles. But be tactical about when and with which exercises you push yourself. You can take the dumbbell skull crusher to failure as long as you do it later in your workout (so as not to impact your other lifts). It’s relatively safe, too. If you feel like you can’t do another rep, slowly lower the dumbbells next to your ears and then drop them on the floor. 

Dumbbell Skull Crusher—Muscles Worked

Primary Muscle

• Triceps brachii

Secondary Muscles

• Anterior deltoid 

• Forearm muscles

The dumbbell skull crusher is an isolation exercise that targets one muscle with a single joint movement. In this case, that’s your triceps, which consists of three heads: the long, medial head, and lateral heads. Dig deep on any bodybuilding forum; you’ll read gym bro theories on how to target one head over another. Technically, it’s possible, but rest assured that skull crushers will develop the entire triceps.

The tris play a minor role in extending your shoulders behind your torso, so your front deltoids will get minor activation, specifically when the dumbbells pass your forehead and your elbows travel backward. The skull crusher doesn’t build as much grip strength as exercises like the dumbbell row, but squeezing the dumbbells hard during each rep will help you develop a stronger grip.

Avoid These Skull Crusher Mistakes

The dumbbell skull crusher has a fairly flat learning curve. Still, there are a few suggestions that’ll ensure you’re adhering to proper skull crusher form:

• Don’t Lift Too Heavy: Dumbbells are less stable than a barbell (or anything you lift with both hands simultaneously), so you should be mindful of how much weight you lift. Go too heavy and your form will be out of whack, decreasing your triceps engagement and increasing your injury risk. 

• Don’t Let Your Shoulders Move: The correct technique is to have only your elbow joint move during each rep to keep tension on the triceps. The one exception is rolling your upper arms back a couple of inches to increase the stretch on the muscle. If you do this, set them back into place before extending your elbow joint.

• Don’t Let Your Elbows Flare: Your wrists, elbows, and shoulders should form a straight line, and the dumbbells should land right next to your ears at the bottom of the rep. As your triceps fatigue, your form will start to break down, and that’s usually when your elbows begin to flare out. Actively fight to keep your elbows tucked in. Flaring them out disengages your triceps and puts undue strain on your shoulder joint. 

Skull Crusher Variations and Modifications

Close-Grip Bench Press

Why: “You can load this movement heavier than any other triceps exercise,” says Salvatore. “The close-grip bench press is a great way to train your triceps in a way that carries over to strength-focused movements.” 

• Lie back on a bench, feet planted on the ground, a slight arch in your lower back.

• Grip the barbell narrower than your standard bench press grip, with your wrists stacked directly over your shoulders. 

• With your shoulder blades squeezed together, lift the barbell out of the rack until it's directly over your chest.

• Lower the bar toward the bottom of your chest, keeping your elbows close to your sides. 

• Drive the bar up until your arms are locked out.

Dip

Why: “The dip is an actual test of your relative strength, and it can be done anywhere you have access to parallel bars or even study chairs,” says Salvatore. “Dip machines and band-assisted dips are great for beginners, and advanced lifters can add weight between their legs to make the move harder.”

• Position yourself on parallel bars and grip them firmly with arms fully extended, staying completely upright to emphasize triceps.

• Flex your elbows to lower your body until your arms are bent to 90 degrees, and then pause at the bottom of the rep. 

• Push through your palms to raise your body back up until your arms are extended. 

Overhead Triceps Extension

Why: “I am a fan of variation, especially when it comes to a joint as mobile as the shoulder,” says Salvatore. “There are certain benefits to bolstering the shoulder in various positions and planes of movement. The overhead triceps extension also puts the long head of the triceps on stretch and can elicit a great stimulus for growth.”

• Attach an EZ-bar or straight bar to a cable machine set so it's level with your upper back. Grab the bar, twist your body around so you’re facing away from the machine, and tuck your elbows next to your ears with your elbows pointing straight ahead. Lean forward slightly. 

• Keeping your elbows tucked in, extend your elbows to drive the bar straight overhead.

• Lower the weight slowly behind your head by bending only at the elbows, keeping your upper arms in place.

Bodyweight Skull Crusher

Why: “What I love about this variation is the convenience factor,” Salvatore says. You can do it on a weight bench, the side of your couch, or even an ottoman. It’s the perfect exercise for an at-home workout.” 

• Set a barbell on a rack or Smith machine so it's sitting roughly at waist level. 

• Grip the bar with your hands shoulder-width apart and walk your feet back until your body is in a slight pike position

• Start with arms fully extended and elbows locked, keeping your core and glutes tight. Bend your elbows and lower your forehead toward the bar, keeping your elbows tucked in and pointed forward.

• Pause briefly at the bottom when your head is close to the bar.

• Push back to the starting position by extending your elbows fully, keeping your hips pike upwards a bit. (Adjust bar height for difficulty: higher for easier, lower for more challenging.)

Benefits

The most significant benefit of the dumbbell skull crusher is that it isolates your triceps, letting you focus entirely on building strength and size. It’s the perfect accessory move to add to your triceps workout if your goal is bigger arms. Also, your triceps help you finish the top-half of your bench press, so stronger triceps equal stronger presses.

DB Skull Crusher vs. Barbell Skull Crusher

There’s more than one way to crush your skull (lucky you). You can lift dumbbells, kettlebells, a traditional barbell, or even a sandbag—all tools lead to triceps gains. But most people use either a set of dumbbells or a barbell. Both are widely available in just about any gym and allow you to lift the most weight with a solid range of motion. Here’s a quick breakdown of the barbell skull crusher versus the dumbbell skull crusher:

The biggest advantages dumbbells offer you over a barbell are a freer and longer range of motion. Barbells lock your hands in a palms-up position that puts a touch of torque on the elbow joint. Lifting dumbbells with neutral hands is often a more comfortable hand position for people with achy elbows. You can also better position the dumbbells behind your head to increase the stretch on your triceps. If muscle mass is your priority, go with the dumbbell skull crusher. 

With a barbell, you’re using two limbs to move one implement. Lifting a barbell is more stable, so you can lift much more weight than with dumbbells. If you can do skull crushers with a 100-pound barbell, you still may struggle to handle 50-pound dumbbells in each hand due to the instability. If you’re trying to strengthen your triceps, barbell skull crushers are a good choice.

Key Takeaways

• Dumbbell skull crushers are one of the most effective isolation exercises for building bigger, stronger triceps.

• This exercise primarily targets all three heads of the triceps, and also trains the shoulders and forearms to a lesser degree.

• Program skull crushers later in your workout, use 6-20 reps per set, and train close to failure.

• Proper form is key: avoid lifting too heavy, letting your elbows flare, or letting your shoulders move too far backward.

• Variations like close-grip bench presses, overhead triceps extensions, and bodyweight skull crushers add variety and target the muscle differently.

FAQs

Are dumbbell skull crushers good for beginners?

Yes. The mechanics of this exercise are fairly simple. It’s also safe. If you feel like you’re going to fail a rep, drop the dumbbells onto the floor from the bottom position. You don’t need a spotter to do this exercise. 

Can I do these without a bench?

It’s not ideal, but you can do the dumbbell skull crusher on the floor if you can’t get to a bench. You won’t have the clearance to drive your elbows back for a greater triceps stretch on the floor. Instead, lower the dumbbells down and in to touch the tops of your shoulders. 

How heavy should dumbbells be?

It depends on how many reps you’re doing; the fewer reps you perform, the heavier the dumbbells you can lift (and vice versa). A good rule of thumb is to leave two reps in the tank for each set. So, if you’re aiming for 10 reps, pick a weight where you can do at most 12 repetitions. 

What if I feel pain in my elbows?

Stop doing the exercise if you feel pain in your elbow joint. If you have a preexisting injury, always consult your doctor before performing a new routine that affects the area. 

Andrew Gutman is a NASM-CPT and health and fitness journalist with bylines in Men’s Health, Gear Patrol, Men’s Journal, and Insider Health. He’s the former Training Editor of Muscle & Fitness and FLEX, and the former Editor-in-Chief of BarBend.com. When he’s not writing, he’s lifting, rolling on the mats (he’s a BJJ purple belt), or reading to his son.

This article was reviewed by Ashley Boyer, ACE-CPT, for accuracy.