How to Do It
- Lie on a flat bench holding a barbell, EZ-bar, or dumbbells with arms extended straight above your shoulders.
- Keep your upper arms fixed and vertical, only bending at the elbows for the entire movement.
- Lower the weight by bending your elbows until it reaches just above or behind your forehead.
- Keep your elbows pointed at the ceiling throughout the descent rather than letting them flare outward.
- Extend your elbows to press the weight back to the starting position, stopping just short of a hard lockout to keep tension on the triceps.
Common Mistakes
- Letting the elbows drift forward or backward instead of staying fixed in one vertical position throughout the set.
- Lowering the weight too far past the head, which puts unnecessary strain on the elbow joint.
- Using shoulder movement to help lower and raise the weight instead of isolating the motion at the elbow.
- Using a load that makes the elbows flare or the shoulders swing instead of keeping a repeatable path.
The skull crusher, more formally a lying triceps extension, trains the triceps with the upper arm positioned above the torso. Because the long head crosses the shoulder, changing upper-arm position changes its working length.
An EZ bar offers an angled shared grip, while dumbbells let each wrist find its own path. Choose the implement you can lower, extend, and return to the supports without wrist or elbow discomfort.
Combine it with tricep pushdowns in a superset on arm day to train the long head and lateral/medial heads in the same session.
Muscles Worked by the Skull Crusher
The skull crusher predominantly loads the triceps during elbow extension. The shoulder stabilisers and forearms also contribute, and the exact distribution among the triceps heads cannot be inferred from sensation alone.
- Primary: triceps brachii, particularly the long head
- Secondary: forearm flexors, which stabilize the grip on the bar or dumbbells
- Stabilizers: anterior deltoids and shoulder stabilizers, which keep the upper arm fixed and vertical instead of drifting
Because the upper arm stays overhead throughout, the long head of the triceps stretches under load in a way that pushdowns, which keep the arm at your side, do not replicate.[1][2]
Skull Crusher vs Tricep Extension
Both emphasise elbow extension with the upper arm elevated, but body position, resistance, and equipment set them apart.
The skull crusher, done lying on a bench, bends only at the elbow with the upper arm fixed vertically, letting you use a straight bar, EZ-bar, or dumbbells. The seated or standing overhead tricep extension moves through a similar elbow path but from a vertical torso position, usually with a single dumbbell or cable, and tends to allow a slightly greater stretch at the bottom.
| Skull Crusher | Overhead Tricep Extension | |
|---|---|---|
| Body position | Lying on a bench | Seated or standing |
| Equipment | Barbell, EZ-bar, dumbbells | Dumbbell or cable, usually single |
| Stretch at bottom | Moderate | Slightly greater |
| Joint comfort | Depends on grip, range, and load | Depends on grip, range, and torso control |
Rotate between the two if one starts to irritate your elbows, since the joint stress profile differs slightly even though the target muscle is the same.
Skull Crusher Alternatives
- Tricep pushdown: trades the overhead stretch for constant cable tension, easier on the elbows for lifters who find skull crushers uncomfortable.
- Overhead tricep extension: a seated or standing variation with a similar stretch, using a single dumbbell or cable instead of a bar.
- Close-grip bench press: shifts from isolation to a compound press, adding triceps volume alongside chest and shoulder work.
- Dumbbell shoulder press: not a direct substitute, but a useful compound pairing on the same push day for total triceps volume.
If elbow discomfort persists after reducing load and range, stop the exercise and seek qualified assessment rather than continuing to test painful variations.
Elbow Calibration and Progression Log
Set the bench so your head, upper back, and pelvis are supported, and use a spotter for a heavy barbell setup. Start with an EZ bar or dumbbells if a straight bar makes the wrists uncomfortable. Test the first repetition with the weight over the shoulders, then lower toward the forehead or slightly behind it while keeping the upper arms mostly fixed. Film from the side: the elbow should flex and extend without the shoulders swinging the load. If the elbows flare or the bar path changes, reduce the load before adding repetitions.
Regress to a cable extension, a lighter dumbbell, or a shorter comfortable range if the elbow is the limiting joint. Progress by keeping the same path, adding a pause near the controlled stretch, then adding repetitions, and only then increasing load. Log implement, grip, range, tempo, repetitions, and elbow comfort after each set. Leave one to three clean reps in reserve. Stop for sharp pain, swelling, locking, numbness, or weakness and seek qualified assessment for persistent symptoms. The tricep pushdown is a useful non-overhead comparison, while the arm day workout covers placement. General progressive-training guidance comes from the ACSM position stand, not a universal requirement to train this exercise to failure.
For the pure-extension option when a JM press’s pressing component is not the actual priority, see JM press alternatives, which compares this exercise with a close-grip bench press and an overhead tricep extension.
References
- Anaerobic and Muscle Endurance Development: Lifting Guidelines. National Strength and Conditioning Association (2017)Back to claim
- American College of Sports Medicine Position Stand. Resistance Training Prescription for Muscle Function, Hypertrophy, and Physical Performance in Healthy Adults: An Overview of Reviews. Medicine & Science in Sports & Exercise (2026)Back to claim
- Updating ACSM's Recommendations for Exercise Preparticipation Health Screening. Medicine & Science in Sports & Exercise (2015)Back to claim
See our exercise methodology for how this evidence is applied and its limits.
Frequently Asked Questions
- Should a skull crusher go behind the head?
- No, a skull crusher should lower the weight toward or just behind your forehead, not all the way behind your head. Keep your upper arms fixed and vertical throughout, bending only at the elbows, and stop the descent once the weight reaches just above or slightly behind your forehead to avoid unnecessary strain on the elbow joint.
- How do you know if you're doing skull crushers correctly?
- You are doing skull crushers correctly if your upper arms stay fixed and vertical throughout the set, your elbows point at the ceiling instead of flaring outward, and the weight lowers to just above your forehead before pressing back up. If your shoulders move to help lift the weight, the load is too heavy for strict form.
- What are skull crushers good for?
- Skull crushers train elbow extension and can add direct triceps work after pressing. The long head crosses the shoulder, so upper-arm position changes its length; keep the load and range comfortable rather than assuming one bar path targets it exclusively.
- Are skull crushers actually effective?
- They can be effective when you progressively load a controlled elbow-extension path. An EZ bar or dumbbells may feel more comfortable because they allow different wrist positions, but no implement guarantees less strain or the same result for every lifter.
- How to correctly do skull crushers?
- To do skull crushers correctly, lie on a flat bench with your arms extended straight above your shoulders, then bend only at the elbows to lower the weight toward your forehead while keeping your upper arms fixed and vertical. Press back up without letting your elbows flare outward, and stop just short of a hard lockout to keep tension on the triceps.
- How to EZ bar skullcrusher?
- To do an EZ-bar skull crusher, grip the angled bends of the bar with a shoulder-width, semi-supinated grip, which is easier on the wrists than a straight bar. Follow the same form as the standard version: upper arms fixed and vertical, elbows lowering the bar toward your forehead, then pressing back to a near-lockout.