Have you ever heard of a cooler-sounding exercise than the notorious skull crusher? Of course not, because nothing can beat feeling like a warrior and bragging about skull-crushing twice a week. And while the name might sound a little scary, the effects of performing this exercise are pretty wonderful.
Skull crushers are a triceps extension exercise that will help you develop these muscles like never before. Yet many guys either skip them because of elbow pain or do them so badly that they never see their impressive mass-building potential.
As with anything else, your gains will depend on the way you perform it. In this article, you’ll learn how to do skull crushers with proper form, 5 variations that hit your triceps from different angles, the most common mistakes, and the best skull crusher alternatives if the classic version bothers your elbows.
What Are Skull Crushers (Lying Triceps Extensions)?
Skull crushers are a single-joint (isolation) exercise for your triceps. You lie on your back, most often on a bench, holding a weight above you with straight arms, then bend only at your elbows to lower the weight toward your forehead – hence the name – and extend your arms back up.
You’ll also hear them called lying triceps extensions or French presses. It’s the same exercise, so if you see any of these names in a workout program, now you know what to do.
What Muscles Do Skull Crushers Work?
Your triceps brachii is the big muscle on the back of your upper arm, between your elbow and your shoulder – and it makes up about two thirds of your upper arm size. If you want bigger arms, you need to train your triceps, not just your biceps.
It has three heads – a lateral, a medial and a long head. The lateral head is on the outer side of the upper arm, and the medial head lies deeper, closer to the elbow. The long head runs down the back of your arm, and it’s the biggest one too. It’s also the only head that crosses your shoulder joint, which is why the position of your arms changes how hard it works.
Skull crushers hit all three heads, and because your arms are angled slightly back over your head, they put a good stretch on the long head. Your forearms, shoulders and chest work a little to stabilize the weight, but your triceps do almost all of the work.
How to Do Skull Crushers
Here’s how to do the classic skull crusher, or lying triceps extension, with an EZ curl bar:
- Lie on your back on a flat bench with your feet flat on the floor. Your head should be near the end of the bench, but supported.
- Grab the EZ bar with an overhand grip, hands about shoulder-width apart. Press it up so your arms are straight above your chest.
- Let your arms drift back slightly, so they point a little behind vertical, toward your head. This keeps tension on your triceps at the top instead of letting the weight rest on your locked joints.
- Keeping your upper arms still, bend your elbows and slowly lower the bar toward your forehead, or just behind your head.
- Stop when your forearms are just past parallel to the floor, or the bar is an inch or two from your head.
- Squeeze your triceps and extend your elbows to bring the bar back up. Repeat.
The key is to keep your upper arms as still as possible and point your elbows forward, not out to the sides. It might be tempting to bring your shoulders into the lift, but then you’ll be getting a shoulder and chest workout instead of one for your triceps. If you can’t keep your upper arms still, the weight is too heavy.
5 Skull Crusher Variations
Although the classic skull crusher can undoubtedly produce significant results, there are other ways to do it that add variety to your workout and boost your gains even further. Changing the equipment and the angle of the bench changes how your triceps are loaded.
#1. Barbell or EZ-Bar Skull Crusher
This is the classic version described above, and it lets you use the most weight because the load is spread across both arms. If you have access to an EZ bar, use that – the angled grip is much easier on your wrists and elbows than a straight bar.
No bench? You can do skull crushers lying on the floor too. The floor stops your arms at the bottom, which shortens the range of motion a little, but it’s a good option at home and many people find it easier on the shoulders.
Be careful with heavy weights though – with a bar over your face, a failed rep could literally crush your skull. Choose a weight you can control, and don’t train to failure without a spotter.
#2. Dumbbell Skull Crusher (Lying Dumbbell Triceps Extension)
People are divided on the subject of dumbbell skull crushers. On one side, they won’t let you lift as much as with a barbell. But they have a positive side too: they make each of your arms work individually, without the support of the other arm, so your stronger arm can’t take over the lift. That makes them great for fixing strength imbalances.
Dumbbells also let you change your grip. A neutral (hammer) grip, with your palms facing each other, is easier on the elbows and wrists for many people. Lower the dumbbells beside your head rather than toward your forehead.
#3. Incline Skull Crusher
Doing skull crushers on an incline bench moves your arms closer to an overhead position, which stretches the long head of your triceps even more. That’s a good thing: in a 2023 study, overhead triceps extensions built noticeably more triceps size – especially in the long head – than pushdowns, where the arms stay by your sides.
Set the bench to a low incline of about 15-30 degrees – if it’s too steep, a big part of the resistance comes off your triceps. Grab an EZ bar or dumbbells, extend your arms in line with your torso above your head, then slowly lower the weight in a semicircular motion behind your head. Squeeze your triceps and push the weight back up. Start off with a lighter weight and add more when your form is perfect.
#4. Decline Skull Crusher
Using a decline bench is a great alternative to the classic version. Because your arms end up closer to your sides, the decline version puts more of the work on the lateral and medial heads. Many people also feel that decline skull crushers are easier on their elbow joints, and you can usually handle a little more weight.
Once you position yourself on the bench, secure your legs and grab the bar with a close grip. Hold it straight above your chest, arms locked and elbows in. As you inhale, lower the bar by moving your forearms in a semicircular motion toward you until the bar lightly touches your forehead. As you exhale, squeeze your triceps and lift the bar back up.
#5. Triceps Extension Push-Up (Bodyweight Skull Crusher)
No weights? No problem. This bodyweight exercise works your triceps in the same way as a skull crusher, so it’s ideal when you train at home or equipment is unavailable.
Start in a forearm plank, with your elbows under your shoulders. Keeping your body in a straight line, push through your palms and straighten your arms until you’re in a push-up position. Then slowly lower yourself back onto your forearms. It’s harder than it looks – if you can’t do it on your toes, start on your knees.
Skull Crusher Alternatives
Skull crushers are a great exercise, but they aren’t for everyone. As with other single-joint exercises, the long lever can cause elbow pain, and that’s the main reason some people avoid them at all costs. If skull crushers bother your elbows, or you just want some variety, these are the best skull crusher alternatives:
- Overhead (vertical) triceps extension. The closest alternative – sitting or standing with a straight back, hold a dumbbell, EZ bar or cable over your head and lower it behind your head. It trains your triceps in a stretched, overhead position, just like an incline skull crusher. The cable version keeps constant tension on your triceps and is easy on the elbows for most people.
- Cable pushdowns. The most elbow-friendly triceps exercise, and great for high reps. They mostly hit the lateral and medial heads, so pair them with an overhead movement.
- Close-grip bench press. A compound exercise that lets you go heavy, using your chest and shoulders too. Keep your hands about shoulder-width apart – any closer just stresses your wrists.
- Triceps dips. One of the best bodyweight triceps builders. Keep your torso upright to keep the focus on your triceps.
- Diamond push-ups. A no-equipment alternative you can do anywhere.
Looking for more elbow-friendly options? Here are 3 joint-friendly moves for bigger triceps.
Common Skull Crusher Mistakes
- Flaring your elbows. If you find yourself constantly flaring your elbows out to the sides to finish the rep, the weight is too heavy. Reduce it and keep your elbows pointing forward.
- Moving your upper arms. If your upper arms swing back and forth, your shoulders and lats take over. Keep them still and let your elbows do the moving.
- Using momentum. Don’t raise your hips off the bench or bounce the weight up. It increases your risk of injury and makes the exercise less effective.
- Going too heavy. Skull crushers are not a max-strength exercise. Heavy, sloppy reps are the fastest way to sore elbows.
- Using a straight bar if your wrists hurt. Switch to an EZ bar or dumbbells – they put much less stress on your wrists.
- Doing them all year round. Even with good form, elbow pain can creep up if you do skull crushers often for months on end. Rotate them with the alternatives above every few weeks.
Sets and Reps
For best results, keep your reps in the moderate to high range: 3-4 sets of 8-15 reps, with a full range of motion on every rep. Do them after your heavy compound pressing exercises, like the bench press or close-grip bench press, once or twice a week. Here’s more on targeting the triceps long head for maximal growth.
Conclusion
Your biceps have the curls, and your triceps have the skull crushers. Do them with proper form – upper arms still, elbows in, controlled reps – and they’re one of the best exercises for bigger triceps and bigger arms. Play with the variations in equipment and bench angle to hit your triceps from different angles, and swap in an alternative whenever your elbows need a break. Start experimenting and watch your triceps grow!
You might like: The 4 Best Muscle-Building Triceps Exercises
