Lying Dumbbell Extension
The dumbbell skullcrusher is a lying triceps extension: on a flat bench, you bend at the elbows to bring two dumbbells down beside your head, then straighten your arms to press them back up. It works all three heads of the triceps, and its palms-in grip and independent arms make it a common alternative to the barbell skullcrusher.
Also called: DB Lying Tricep Extension, Lying DB Tricep Extension, Dumbbell Lying Triceps Extension, Neutral-Grip Skullcrusher · Equipment: dumbbell · Pattern: isolation
Step by step
- Sit on the end of a flat bench with a dumbbell in each hand resting on your thighs, then lie back and press the dumbbells up over your chest. Plant your feet flat on the floor.
- Turn your palms to face each other and hold the dumbbells above your shoulders with your arms straight.
- Let your upper arms angle back slightly towards your head, with your elbows pointing up and about shoulder-width apart.
- Bend only at the elbows to bring the dumbbells down beside your head, taking about two seconds, until you feel a deep stretch in the backs of your arms.
- Keep your upper arms still, then straighten your elbows to press the dumbbells back to the start.
- Finish with your arms straight, without letting your upper arms swing forward.
- After the last rep, bring the dumbbells to your chest and sit up with them resting on your thighs.
- Upper arms still, bend only at the elbows
- Dumbbells come down beside your head
- Elbows point up, not out
- Palms facing each other
- Two seconds into the stretch
- Straighten fully at the top
In VALDA, these cues are one tap away on the exercise while you train.
What it trains
| Muscle | Role | Evidence |
|---|---|---|
| Triceps brachii: long head | Prime mover | C |
| Triceps brachii: lateral head | Prime mover | C |
| Triceps brachii: medial head | Secondary | C |
| Anconeus | Secondary | D |
| Forearm flexors | Stabiliser | D |
Evidence grades: A = strong research base · B = good · C = limited · D = coaching consensus.
What goes wrong, and the fix
Elbows flaring out
Fix: Keep your elbows pointing up, about shoulder-width apart.
Upper arms swinging
Fix: Hold your upper arms at a slight backward angle and bend only at the elbows.
Cutting the stretch short
Fix: Bring the dumbbells down until you feel a deep stretch behind your arms.
Dropping into the bottom
Fix: Take about two seconds to bring the dumbbells down beside your head.
One arm leading the other
Fix: Move both dumbbells together and match your reps to the weaker arm.
Dumbbells too heavy to control
Fix: Choose dumbbells you can hold steady at the bottom of every rep.
What the research says
Muscle growth · first choiceGeneral fitness · first choiceStrengthRehab & prehabEndurance
- Arm position — In a 12-week study, triceps extensions with the arm overhead grew the triceps about 20%, against about 14% with the arm at the side, mainly through the long head. The skullcrusher's arm angle sits between the two, and no study has tested it directly.
- Load by goal — Research comparing loads finds maximal strength favours heavier loads, while muscle growth is similar across a wide range of loads when sets are taken close to failure.
- Effort — Studies show sets that finish a few reps short of failure capture most of the growth benefit, and true failure adds only a small extra return.
- Volume and frequency — Research links more weekly sets for a muscle to more growth, with diminishing returns. Around 10 or more hard sets a week has been associated with more growth than fewer than 5, counting pressing work that also trains the triceps, and training a muscle about twice a week is a common way to spread that volume.
Swap it mid-workout
- Dumbbell Skullcrusher
- Dumbbell French Press
- Dumbbell Tricep Extension
- Skull Crushers
- Cable Overhead Tricep Extension
- Overhead Barbell Extension
With VALDA Pro, FLEX offers alternatives like these when you swap an exercise mid-workout.
Log the lying dumbbell extension in VALDA, with these cues one tap away while you train and your history for it in one place.
General information about exercise technique, not medical advice. If you have an injury or a health condition, your healthcare provider is the right person to ask.