The Dumbbell Skull Crusher 101 | How to Build Bigger Triceps!

Dumbbell Skull Crushers

Dumbbell skull crushers, also known as the lying triceps extension, is an effective exercise for anyone attempting to build triceps strength and size. The tricep is one of the most important muscles involved in upper body conditioning.

If you want to improve your upper body strength, size, and aesthetics, dumbbell skull crushers are for you! 

Muscles Worked By Dumbbell Skull Crushers

Primary Muscle Groups:

Contrary to its name, a properly completed skull crusher will not, in fact, crush your skull. Thankfully, your triceps prevent that from happening. The triceps muscle is comprised of three “heads:” the long, medial, and lateral head.

While the lying triceps extension works all three heads of the muscle, it especially targets the long and lateral heads of the triceps.


Secondary Muscle Groups:

Although the dumbbell skull crusher is an isolation exercise for your triceps, several other muscle groups are secondarily worked. Your anterior and posterior deltoids in your shoulders contract to stabilize your arms.

The clavicular head of your pectoralis major, located in your upper chest, also receives tension and stabilizes your upper body during the lying triceps extension. Lastly, the latissimus dorsi, the largest muscle of your back, plays a role in stabilization as well. 

Dumbbell Skull Crusher Benefits

1. Stronger Triceps

The dumbbell skull crusher is one of the premier exercises proven to strengthen your triceps muscle. A stronger tricep is crucial for completing so many other upper body exercises. Without strong triceps muscles, it will be difficult to properly train your chest and shoulders.

Not only does building tricep strength improve your overall arm strength, but it will make you better in a variety of exercises at the gym. 

2. Triceps Isolation

The lying triceps extension is an isolation exercise. This means that unlike other exercises such as the pushup or bench press, the dumbbell skull crusher specifically targets the tricep muscle.

This is especially important for bodybuilders, athletes, or anyone else seeking to focus on improving the strength and appearance of their triceps.

3. Low Stress on the Wrists 

Throughout the dumbbell skull crusher, your wrists remain in a neutral position. In other words, there is no rotation or added stress placed upon your wrists.

If you find other heavier straining exercises like the close-grip bench press or weighted dips uncomfortable, try out the dumbbell skull crusher and take the tension off of those wrists. 

How To Do Dumbbell Skull Crushers 


For this exercise, you will need a pair of dumbbells.


a) Lie down on a flat bench or the ground with your feet planted firmly onto the floor.

b) Hold the dumbbells above your chest with your palms facing each other and engage your core.


a) With your elbows in a fixed position, hinge your elbows to slowly bring the dumbbells down just behind your ears. Inhale.

b) Contract your triceps to extend your arms back into the straight position at the top. Exhale. 

c) Repeat this motion for your desired number of reps. 


If you are new to the lying triceps extension, choose a light weight to begin and complete 3-4 sets of 10-15 reps. If you are more comfortable with the form, grab a pair of heavier dumbbells and stick to the 6-8 rep range for 3-4 sets. 

Dumbbell Skull Crushers Mistakes

1. Flaring of the Elbows 

Many weightlifters tend to flare out their elbows when doing the dumbbell skull crushers exercise. When the elbows flare out, we risk injury to our shoulders and we remove tension from the triceps.

Make sure to keep your elbows in to practice proper form.

2. Excessive Movement of the Elbows/Shoulders

During the lying triceps extension, you want to make sure your elbows are in a fixed position. Often times, people tend to rock their shoulders back as the weight comes down. This forces the elbows to shift backwards as well.

While some movement is natural, too much movement will force your lats to activate to bring the dumbbells upwards. If you want to solely train your triceps, keep those elbows and shoulders in a stationary position. 

3. Arching Your Back

Arching your back during the lying triceps extension compromises the stability of your body positioning while completing this exercise.

Instead of arching your back, place your feet firmly against the ground, engage your core, and keep your back flat against the bench or ground. 

Dumbbell Skull Crusher Variations

1. Bodyweight Skull Crushers

No equipment? No problem! You can do a skull crusher with just your body weight. First, set up in a plank position with your hands together. Then contract your triceps and push your body off the ground and slightly backward.

Return to the plank position and repeat!


2. Barbell Skull Crushers

The barbell skull crusher is another great variation of the dumbbell skull crusher. This variation is especially useful if you want to add heavier weight to the exercise.


3. 1-Arm Skull Crushers

You can also use the skull crusher to train your arms individually to fix any potential muscle imbalances in your arms. Keep your core engaged for stability during this variation!


Dumbbell Skull Crusher Alternatives

If you enjoyed the dumbbell skull crusher, check out these triceps exercises to improve your upper body training:

1. Alternating Triceps Pushdown:

The alternating triceps pushdown is a powerful triceps isolation exercise. Keep your elbows tucked in to your sides and contract your triceps at the bottom of each rep.

2. Overhead Triceps Extension (with rope)

The overhead triceps extension strengthens the long head of your triceps. As you extend upwards, pull the rope apart and contract your triceps at the top of the rep.


3. Close Grip Bench Press

The close grip bench press engages your triceps significantly more than the traditional bench press. Bring the weight down just below your chest and contract your tricep to press upwards. Repeat!

Looking For More Triceps Workouts?

Follow along to this dumbbell triceps workout with tempo!

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.mike kenlerExercises & fitness tips