The single dumbbell skull crusher is atricepsisolation exercise performed lying on a flat bench with one dumbbell held in both hands and lowered toward the forehead by bending the elbows. Cupping one bell puts the hands close together in a neutral grip, so the elbows stay tucked and the load sits at a single point between the hands. With the upper arms tilted slightly back past vertical, the long head gets a stretch a cable pressdown never reaches, though less than an incline French press. Lifters use it as a second triceps movement on arm or push day.
What Muscles Does the Single Dumbbell Skull Crusher Work?
- Primary: Triceps brachii (long and lateral heads)
- Secondary: Triceps brachii (medial head), anconeus
- Tertiary: Posterior deltoid, latissimus dorsi, forearm flexors (grip)
How Do You Set Up for the Single Dumbbell Skull Crusher?
Sit on a flat bench with one dumbbell standing on your thigh. Cup the underside of the top plate with both palms, thumbs around the handle, and lie back with your feet flat and your head fully on the bench. Press the dumbbell up over your chest, then tilt the upper arms back until they point slightly behind vertical, elbows shoulder width apart and pointing at the ceiling.
How Do You Perform the Single Dumbbell Skull Crusher?
- Fix the upper arms slightly past vertical with the elbows shoulder width apart and the dumbbell over your face.
- Bend the elbows to lower the dumbbell toward the top of your forehead, keeping the upper arms still.
- Reach the bottom when the forearms pass horizontal and the bell hovers just above the hairline.
- Pause for a beat with the triceps fully stretched and the elbows still pointing up.
- Extend the elbows to drive the dumbbell back up, stopping just short of a locked arm.
- Reset the upper-arm angle, then lower into the next rep without letting the elbows drift wide.
What Are the Key Form Cues?
- Elbows point at the ceiling: hold them shoulder width and still so the forearm does all the moving and the shoulder none of it.
- Upper arms lean back a touch: a few degrees past vertical keeps the long head under tension at the top instead of stacking the bell over the elbow.
- Pull the bell toward the hairline, not the nose, so the elbow bends deep.
- Squeeze the bell between your palms so it cannot tip toward one hand.
- Slow the last third of the descent, where the stretch peaks.
What Are the Most Common Mistakes?
- Picking a dumbbell heavier than the bottom position can hold: the elbows flare, the shoulders roll and the bell drops toward the face; choose a weight you can lower under control to the hairline.
- Letting the elbows drift wide: the load moves to the shoulders and the bell path shortens; keep them shoulder width and pointing up.
- Turning the rep into a pullover: the upper arms swing toward the head and the lats lift the bell; keep the upper arm angle fixed.
- Locking the elbows hard at the top: the joint takes the load and the triceps rest; stop a few degrees short of straight.
- Lowering the bell to the nose or chin: the range shortens and the elbow stacks under the bell; aim for the top of the forehead.
What Are the Best Single Dumbbell Skull Crusher Variations?
- Two-dumbbell skull crusher: a bell in each hand lets the wrists set their own angle and each arm work alone.
- Incline single dumbbell skull crusher: a 30-degree incline puts the upper arms further behind the head for a longer long head stretch.
- Single arm dumbbell French press: one bell overhead, standing, with the trunk resisting a side lean.
- Floor skull crusher: the floor stops the elbows from drifting and limits the bottom range for beginners.
- EZ bar skull crusher: wider hands and an angled grip for heavier loading.
How Do You Progress the Single Dumbbell Skull Crusher?
- Move up 5 pounds once every set reaches the top of the rep range with the elbows still pointing up.
- Build from 10 reps a set to 15 before each weight jump.
- Add a fourth set when three no longer leave the triceps fatigued.
- Lower on a three-count, or pause for two seconds at the hairline.
How Should You Program the Single Dumbbell Skull Crusher?
Place the single dumbbell skull crusher after a press or a dip in an arm or push session, once or twice a week. Work 3 to 4 sets of 10 to 15 reps with 60 to 90 seconds of rest. It pairs with a cable pressdown, which loads the triceps at a short length after the skull crusher has loaded the stretch. Stand the dumbbell on your thigh between sets.
