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Dumbbell Single-Arm Skull Crusher

Intermediate

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A unilateral dumbbell isolation exercise targeting the triceps brachii to build arm strength and hypertrophy; performed lying on a bench to focus on one arm at a time and correct imbalances.

About Exercise

Equipment

Dumbbells, Flat Bench

Difficulty

2/5 • Intermediate

Primary Muscle Groups

Triceps

Secondary Muscles

Shoulders, Forearms

Accessory Muscles

Abs

Popularity Score

Goals

Strength

Hypertrophy

Training Style

Bodybuilding

Setup Requirements

Requires Rack

Requires Bench

Yes

Requires Spotter

Space Needed

Small

Noise Level

Low

Muscle Breakdown

View Muscle Map

Triceps

10/10

Long Head, Lateral Head, Medial Head

Shoulders

4/10

Anterior Delts

Forearms

3/10

Abs

2/10

Programming

Typical Rep Range

8-15 reps

Rest Between Sets

60-90 seconds

How to Perform

Lie supine on a flat bench with feet flat on the floor for stability. Hold a dumbbell in one hand with a neutral grip, extending your arm straight up above your shoulder.

Brace your core and keep your upper arm perpendicular to the floor.
Bend only at the elbow to lower the dumbbell in an arc toward your head.
Lower until your forearm is nearly parallel to the floor.
Pause briefly to feel the stretch in your triceps.
Contract your triceps to extend your elbow and press the dumbbell back up.
Squeeze your triceps at the top without locking your elbow.
Switch arms and repeat for equal reps.

Coaching Tips

Form Cues

Fix upper arm in place
Elbow points to ceiling
Squeeze triceps hard
Control the arc path

Breathing

Inhale as you lower the dumbbell, exhale as you press it back up while bracing your core.

Tempo

3-1-1

Range of Motion

Lower the dumbbell until your forearm is parallel to the floor or you feel a stretch in the triceps; extend to a soft elbow position without hyperextending.

Safety

Safety Notes

Avoid lowering directly onto your face
Use lighter weight if form breaks
Stop if sharp elbow or shoulder pain occurs
Keep back pressed into bench to avoid arching

Spotting

For heavier weights, have a spotter ready to assist by supporting your elbow or taking the dumbbell; otherwise, use safeties like pins if on a machine alternative.