# Dumbbell Skull Crusher: how to do it

- Main muscles: triceps
- Equipment: dumbbell, bench
- Level: intermediate
- 3D demo (side view): https://media.trainaq.com/exercises/dumbbell_skull_crusher/3daef2ad56/side-m-720.mp4

## Steps

1. Lie on a flat bench, feet flat, dumbbells straight up over your shoulders.
2. Turn your palms to face each other, elbows pointing to your knees.
3. Bend your elbows to lower the dumbbells beside your head.
4. Straighten your arms to return, keeping your upper arms still.

## Cues

- Upper arms stay vertical
- Elbows in, pointing forward
- Slow down, smooth up

## Common mistakes

- Elbows flaring out; keep them shoulder-width and pointing to your knees.
- Moving the upper arms; only bend and straighten the elbows.
- Lowering too fast; control the dumbbells beside your head.

## Starting position

Lying on the back on a flat bench (pad top about 45 cm high). Head, upper back and hips on the pad; feet flat on the floor about hip-width, knees about 90° ("five-point contact"). Natural low-back curve, no big arch; shoulder blades set down. A dumbbell in each hand, closed neutral grip (palms facing each other), thumbs round the handles, wrists straight.

## The movement

Only the elbows move. The dumbbells travel in an arc round the elbows, down and towards the head, past the sides of the forehead, and back up the same arc. The upper arms stay vertical and still; the shoulders do not move. Torso, hips and feet stay still on the bench.

## End position

(turnaround point): elbows bent so the dumbbells sit beside the head, at about temple to ear level, just clear of it. Upper arms still vertical, or tipped back towards the head by no more than 10–15°. Elbows still shoulder-width apart.

## Tempo

Lower 2 s, pause 0.3 s, extend 1.2 s, hold 0.3 s.

## Form in numbers

| Measure | Target | Good range | Sources |
| --- | --- | --- | --- |
| Bench | flat | pad top 40–50 cm |  |
| Upper arm angle (from vertical) | 0° | 0–15° tipped towards the head |  |
| Elbow at top | 175° | 170–180° (no snap) |  |
| Dumbbell at bottom | beside temple/ear | forehead to ear level, 2–5 cm clear of the head |  |
| Elbow spacing | shoulder width | 0.9–1.1× shoulder width |  |
| Wrist extension | 0° | 0–10° |  |

## Sources

1. [[ExRx.net: Dumbbell Lying Triceps Extension (Internet Archive copy)](](https://web.archive.org/web/2023/https://exrx.net/WeightExercises/Triceps/DBLyingTriExt)
2. [[ACE: Lying Barbell Triceps Extensions](](https://www.acefitness.org/resources/everyone/exercise-library/36/lying-barbell-triceps-extensions/)
3. [[Achievable: CSCS exercise technique list, part 5 (third-party paraphrase of NSCA technique, lying triceps extension)](](https://app.achievable.me/study/cscs/learn/exercise-technique-for-free-weight-and-machine-training-exercise-list-part-5)

Source: https://trainaq.com/exercises/dumbbell-skull-crusher