How to do the Single Arm Dumbbell Skull Crusher
- Lie on a bench, feet flat, one dumbbell above your shoulder.
- Hold the working upper arm with your free hand, elbow pointing up.
- Bend your elbow to lower the dumbbell beside your head.
- Straighten your arm back up, then switch arms after all reps.
Full technique — 7 steps
- Lie on a flat bench with feet planted and one dumbbell held above your shoulder.
- Use a neutral grip and set your upper arm nearly vertical with the elbow pointing upward.
- Hold the working upper arm near the elbow with your free hand.
- Bend your elbow to lower the dumbbell beside your head.
- Stop when your elbow is fully bent and your upper arm has stayed in place.
- Extend your elbow to drive the dumbbell back up until your arm is straight over your shoulder.
- Finish all reps on one side, then switch arms and repeat.
Common mistakes
- Upper arm drifting backward
- Turning it into a press
- Cutting the bottom range short
- Stopping short of full extension
- Pushing the arm with the free hand
Form cues
- Lower beside the head
- Use a neutral grip
- Keep upper arm vertical
- Hold arm with free hand
- Straighten arm completely
Substitutes by equipment
Same muscles, same movement — pick the version you have the gear for.
Resistance bands
- Resistance Band Floor Skull Crusher Same level
- Single Arm Overhead Resistance Band Triceps Extension Same level
Cable machine
- Triceps Pushdown (Reverse Grip) Same level
- Cable Overhead Triceps Extension (EZ Bar) Harder
Kettlebell
Barbell
- Barbell Skull Crusher Harder
Where to start and where to go next
Same muscles, same movement. Too hard for now — step down; once it gets easy — step up.
- This exercise Single Arm Dumbbell Skull Crusher
- Harder Dumbbell Overhead Triceps Extension
- Harder Dumbbell Skull Crusher
Quick answers
What muscles does the Single Arm Dumbbell Skull Crusher work?
Primary: Triceps 10/10. Also works: Forearms 3/10, Rotator Cuff 3/10.
When should I do the Single Arm Dumbbell Skull Crusher in a workout?
Finisher. Goes last, once the heavy work is done. ≈ 8 min with rest.
How many sets and reps of the Single Arm Dumbbell Skull Crusher?
Strength: 3–4 sets of 6–8 reps, rest 1 min 30 s, 2–3 reps in reserve. Muscle growth: 3–4 sets of 8–12 reps, rest 1 min, 2–3 reps in reserve. Endurance: 2–3 sets of 15–20 reps, rest 45 s, 3–4 reps in reserve.
What can I do instead of the Single Arm Dumbbell Skull Crusher?
Resistance bands: Resistance Band Floor Skull Crusher, Single Arm Overhead Resistance Band Triceps Extension. Cable machine: Triceps Pushdown (Reverse Grip), Cable Overhead Triceps Extension (EZ Bar). Kettlebell: Kettlebell Overhead Triceps Extension, Kettlebell Skull Crusher. Barbell: Barbell Skull Crusher.
What is a harder version of the Single Arm Dumbbell Skull Crusher?
Dumbbell Overhead Triceps Extension (Beginner), Dumbbell Skull Crusher (Intermediate).
