Skull crushers are a triceps isolation exercise: with your elbows fixed and pointing up, you flex and extend only the forearm, lowering a barbell or dumbbells toward your forehead. The defining feature is that the shoulders stay still, so the movement is pure elbow extension, which loads the long head of the triceps heavily. It is one of the most effective exercises for adding arm size, and also one of the most misunderstood technically.
Muscles worked
The triceps brachii has three heads: long, lateral and medial. All three extend the elbow, but the long head also crosses the shoulder joint, so how much it works depends on arm position. When skull crushers are performed with the arms angled slightly back (toward or behind the head), the long head is placed on stretch and does a lot of work, which is exactly why lifters value this movement for complete triceps development.
- Prime mover: triceps brachii (long-head emphasis with arms angled back).
- Synergists / stabilizers: anconeus, forearm muscles, front delt working isometrically.
Unlike presses (bench, dips) that share the load with chest and shoulders, here the triceps is isolated with no other large muscle helping out. To train the whole arm, pair skull crushers with bicep curl variations as antagonists.
Step-by-step technique
- Set-up: lie on a flat bench, feet planted, hips and back supported. Grab an EZ bar with a grip slightly narrower than shoulder width.
- Starting position: press the bar up, but instead of holding your arms perfectly vertical, angle them slightly back toward your head to keep constant tension on the triceps even at the top.
- Fixed elbows: this is the make-or-break detail. Your elbows must stay tucked and in the same position for the whole set. They should not flare out to the sides or drift forward and backward.
- Lowering: flex only the forearm, bringing the bar toward your forehead or just behind your head. Control it for 2-3 seconds and feel the triceps stretch.
- Pressing back: extend the elbow and return to the start by driving with the triceps, no jerking. Stop just short of full lockout so you keep tension off the joint.
- Breathing: inhale on the way down, exhale on the way up.
The ideal bar path is not perfectly vertical: taking the load toward your forehead or behind your head (rather than to your chest) keeps the elbows at the right angle and maximizes the long-head stretch.
Main variations
Each variation changes the resistance curve and the stress on the joint. Choose based on elbow comfort, equipment and goal.
| Variation | Equipment | Emphasis / elbow load | When to use it |
|---|---|---|---|
| EZ-bar skull crusher | EZ bar | Solid load, wrist-friendly grip | Default for most athletes |
| Dumbbell skull crusher | 2 dumbbells | Unilateral, more joint freedom | If the bar bothers your elbows |
| Standing / overhead extension | Barbell or dumbbell | Maximum long-head stretch | Long-head growth, comfort in stretch |
| Cable skull crusher | High or low cable | Constant tension, joint-friendly | Deload, sore elbows, pump work |
| Lying barbell skull crusher | Straight/EZ bar | Highest horizontal load | Triceps strength, advanced lifters |
The cable version is worth a note: by keeping continuous tension and reducing load spikes at the harshest joint angles, it is often the most tolerable for sensitive elbows. The standing overhead dumbbell version is the best pick for emphasizing the long head under maximal stretch.
Common mistakes
- Elbow pain: the most frequent complaint. It comes from loads that are too heavy, explosive full lockout, or a rigid bar path. Drop the weight, slow the eccentric, switch to the EZ bar or cable and never snap the elbow straight.
- Flaring elbows: if the elbows drift outward, you turn the move into a press and lose the isolation. Keep them tucked and parallel for the whole set.
- Elbows drifting back and forth: if the shoulder contributes, you are no longer isolating the triceps. Picture your elbows nailed in place in space.
- Partial range: stopping halfway down removes the very stretch that makes the exercise work. Lower under control until you feel the tension.
- Ego loading: skull crushers reward technique, not maximal weight. A load you can control for 10-15 clean reps beats one that breaks your bar path.
Programming
Skull crushers are an accessory, not a main lift, so they belong after heavy presses (bench, dips, overhead) in the session. As an isolation move they respond well to moderate-to-high volume and moderate reps.
- Frequency: 1-2 times per week, inside push or arm days.
- Volume: 3-4 sets, often combined with other triceps work (pushdowns, dips).
- Reps: 8-15 per set. Triceps tolerate higher reps well.
- Intensity: stop 1-3 reps shy of failure (RIR 1-3). You do not need to grind to failure every set.
- Progression: apply progressive overload by adding reps before load, to protect the elbows.
A practical example: on a push day you might run flat bench, overhead press, then 3-4 sets of EZ-bar skull crushers for 10-12 reps, finishing with cable pushdowns. If you follow a push pull legs split, skull crushers fit naturally into the push day. Tracking sets, loads and RPE over time is the most reliable way to know if you are progressing: with Athleex you log every set and watch the load curve week after week.
Elbow health
The elbows are the most exposed joint in this exercise. A few good habits cut down on discomfort: warm the triceps up with a couple of light pushdown sets before loading; avoid explosive lockout at the top; vary the angle (cable, dumbbells) if one tool bothers you; and respect recovery days. Occasional load-related tightness is different from sharp, lasting pain: in the latter case, stop and consider seeing a healthcare professional. This article is informational and does not replace medical advice.
Fitting skull crushers into an arm routine
Skull crushers pay off most when they are part of a coherent plan, not an isolated exercise thrown in at random at the end of a session. To build complete triceps it helps to cover three angles of work: stretch, mid-range tension and peak contraction. Skull crushers cover the long-head stretch superbly; cable pushdowns hit the mid-range with constant tension; and a move like a rope pushdown with a final flare, or single-arm extensions, finishes the peak. By rotating these three stimuli across the week you cover the whole muscle without needing dozens of sets.
An example of a balanced arm block for an intermediate athlete, to slot into a push day or a dedicated arm day: EZ-bar skull crushers 3 sets of 10-12 as the main triceps exercise, then cable pushdowns 3 sets of 12-15, followed by barbell curls and hammer curls for the biceps. If you are short on time, pair skull crushers and curls in antagonist supersets: while one group works, the other recovers, and you halve the dead time without losing quality.
Progression on an accessory like this is slower and needs patience. Do not expect to add load every week the way you might on a bench press: on isolated triceps, weight jumps are small and infrequent. The best strategy is double progression, meaning you stay at the same load until you reach the top of the rep range on every set, and only then increase the weight and start again at the bottom of the range. Logging each set stops you fooling yourself from memory: many athletes believe they are progressing when they are only changing their execution. With an accurate log you see whether weekly volume and loads are actually climbing over time, which is the only honest way to know whether your triceps are growing.
One last tip concerns the specific warm-up. The triceps, and in particular the tendons that cross the elbow, respond well to a couple of ramp-up sets that ease you into your working load. Never start with your full weight on the first set: do one or two light sets of pushdowns or low-load skull crushers to bring blood and temperature to the joint. This simple habit reduces elbow discomfort and also improves the connection with the muscle, so your working sets produce more. If you train on a push day, the triceps will already be partly warmed by the heavy presses done earlier, which is another good reason to place skull crushers after bench and overhead work rather than at the start of the session.
FAQ
Do skull crushers hurt your elbows? They should not. Mild discomfort can appear with loads that are too heavy, explosive lockout, or a rigid bar path, but it is not inevitable. To reduce it: use an EZ bar or cables instead of a straight bar, control the eccentric, never snap the elbow straight, and warm the triceps up first. If you feel sharp, persistent joint pain, stop and consider a healthcare professional: overload-related tightness is different from pain that will not settle.
Skull crushers or cable pushdowns, which should I pick? They are not mutually exclusive, they complement each other. Skull crushers, with the arms angled back, put the long head of the triceps on stretch and drive a lot of growth. Cable pushdowns keep constant tension and are gentler on the elbows. The best approach for most athletes is to use both in the same session: skull crushers as the main triceps exercise and pushdowns as a higher-rep finisher.
Straight bar or EZ bar for skull crushers? For most people the EZ bar is preferable: the angled grips cut wrist and elbow stress while still allowing a solid load. The straight bar allows slightly heavier loads but is more demanding on the joints. Dumbbells give even more freedom and work one arm at a time, useful if you notice asymmetries. Try the options and pick whichever gives you a smooth, pain-free bar path.
How often can I train triceps with skull crushers? Once or twice a week is enough for most athletes, slotting them into push or arm days. Triceps recover fairly quickly, but they are already involved in every press (bench, overhead, dips), so there is no need to overdo direct volume. Roughly 6 to 12 total weekly sets for triceps, counting skull crushers and other exercises, is a sensible range to grow without overloading the elbows.
Should I do skull crushers before or after bench press? After. Bench press and other heavy presses are priority multi-joint lifts that need fresh triceps as synergists. If you do skull crushers first, you reach the bench with pre-fatigued triceps and your main-lift performance drops. Place triceps isolation at the end of the session, once the heavy work is done. The exception is intentional pre-exhaustion, an advanced technique to use judiciously.
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