Dumbbell skull crusher
Why it's worth doing
The skull crusher gives the triceps something most compound pushing exercises don't: a deep stretch under load, with the arm overhead instead of pinned to your side. That position stretches the long head of the triceps, the only one of the three that crosses the shoulder joint, far more than a bench press or a cable pushdown ever will, and that stretch under tension is one of the stimuli that contributes most to muscle growth, based on what recent strength training research shows.
Unlike a compound lift, where the triceps only works as a secondary mover and never reaches its own limit because some other muscle group fatigues first, here the triceps is the only thing driving the movement from start to finish. That makes it an efficient way to pile up the direct volume that a bench press or overhead press day leaves unfinished.
The dumbbell version, specifically, solves a problem a straight bar or an EZ bar doesn't: each arm can rotate to whatever elbow and wrist angle feels most comfortable, instead of being forced into the same fixed position as the other hand. That makes it a more accessible option for anyone dealing with elbow or wrist discomfort on the barbell variations.
It's also a simple lift to progress: adding a couple pounds per dumbbell every so often is enough, with no new technique to learn and no dependence on a specific gym machine.
How to do it
- Lie flat on a bench with a dumbbell in each hand, arms extended over your shoulders, palms facing each other.
- Point your elbows at the ceiling, close together, and don't let them flare out to the sides.
- Bend only at the elbow and lower the dumbbells back, behind your head, not toward your forehead.
- Lower until you feel a good stretch in your triceps, without losing tension or banging the weights on the bench.
- Pause briefly at the bottom instead of bouncing the dumbbells to help you back up.
- Extend your elbow back along the same path, without snapping it straight at the top.
- Repeat, keeping your elbow pinned in the same spot for the whole set, on both arms.
Watch the video
Muscles worked
The prime mover is the triceps brachii, and here the long head, the one that crosses the shoulder as well as the elbow, takes on a role it doesn't get in exercises where the arm stays at your side, like cable pushdowns. With the arm overhead, the long head is stretched at the shoulder and the elbow at the same time, putting it under more tension at the bottom of the range than in almost any other triceps variation.
The lateral and medial heads work through the whole range too, mostly near full extension, but what sets this exercise apart from other triceps work is exactly that extra emphasis on the long head.
The main stabilizer is the front delt, which holds the arm vertical over the shoulder for the whole set; if the arm starts drifting forward or back, the shoulder steps in to compensate and the elbow's path loses precision. The wrist flexors and extensors lock the dumbbell in your hand at an angle that shifts slightly with every rep, and the core works isometrically to keep your lower back from lifting off the bench as the weight reaches the bottom of the range.
One practical detail: since this is an exercise where the elbow works with the arm overhead, a person's arm length changes how much weight they can handle with good technique quite a bit more than it does in an exercise where the arm stays at their side.
Common mistakes
- Lowering the dumbbells toward your forehead instead of behind your head: it takes the elbow into its most flexed angle exactly where it's worst to load it, and it's what wears the joint down over time.
- Letting your elbows flare out to the sides: it turns the skull crusher into a lying dumbbell chest press, taking the work off the triceps.
- Bouncing the weight at the bottom to help yourself back up: it replaces, with momentum, exactly the part of the range where the triceps should be producing the force.
- Picking a weight that doesn't let you control the stretch at the bottom: elbow pain in this exercise usually shows up from too much load first, not from bad base technique.
Dumbbells or an EZ bar
Dumbbells or an EZ bar for the skull crusher: total weight moved isn't the only thing that changes here.
The EZ bar locks both hands into the same grip angle, slightly angled to ease the wrist a bit compared to a straight bar. That lets you load more total weight with the same technique, since both hands rise and fall as one unit, with neither side needing to stabilize on its own. The tradeoff is that the angle is the same for everyone, regardless of arm length or shoulder width; for plenty of people, that fixed angle ends up forcing the wrist or elbow, especially over long sets.
Dumbbells, the version on this page, let each arm rotate independently to whatever wrist angle feels most comfortable, and that angle can shift slightly through the range. That makes them the more comfortable option for the wrist and elbow compared to the EZ bar, and they also fix arm-to-arm imbalances a bar can hide. The tradeoff is that you'll typically move somewhat less total weight, since each dumbbell demands its own stability.
The practical call: if your elbow or wrist bothers you with the bar, or there's a strength imbalance between arms, dumbbells are the safer choice. If the goal is moving the most total weight possible and your joints tolerate it without discomfort, the EZ bar usually pays off more for the same effort.
Frequently asked questions
Why lower behind your head instead of toward your forehead?
Because lowering toward your forehead takes the elbow into its most flexed position with the weight farthest from the shoulder, which is exactly the spot that stresses the joint most on every rep. Lowering further back, toward the top and behind your head, keeps the tension on the triceps without demanding that extreme angle from the elbow.
Dumbbells or an EZ bar for this exercise?
With dumbbells, each arm rotates freely to whatever wrist angle feels comfortable, while an EZ bar locks both hands into the same angle regardless of your arm length or shoulder width, which ends up forcing the wrist for plenty of people. That's why the dumbbell version is usually easier on the wrists than the EZ bar, even though the bar lets you move somewhat more total weight.
Is it normal to feel this in my elbow?
A deep stretch feeling in the triceps is expected. A sharp, localized pain in the joint itself is not, and it's usually a sign of lowering too far toward the forehead, letting the elbows flare, or using more weight than the elbow can handle in that position.
How much weight should I start with?
Less than instinct tells you to. Since the elbow works at a heavily flexed angle with the weight far from the body, torque on the joint climbs fast with every pound you add, much faster than in an exercise where the weight stays close to the body through the whole range.
Similar exercises
The skull crusher pairs well with the rest of a week's triceps work, covering an angle other exercises don't. Cable pushdowns train the same muscle with the arm at your side instead of overhead, with constant cable tension from start to finish; rotating between the two across weeks covers the whole muscle from two different positions.
After a vertical pushing session built around the overhead press, where the triceps already worked as a secondary mover without reaching its own limit, adding a skull crusher fills in the direct volume the press alone doesn't give.
If the goal is a compound bodyweight movement, dips train the triceps and chest at the same time, with the advantage of progressing by adding weight instead of stacking more on the dumbbell.