How to Do Skull Crushers: Proper Form, Variations, and Common Mistakes

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Also Known As: Skull crusher, French extension, French press

Targets: Triceps

Equipment Needed: Dumbbells (or barbell), weight bench

Level: Intermediate

The lying triceps extension is an isolation exercise that builds the triceps muscle group in the back of the upper arm. It is also called the skull crusher because if you use poor form, you could endanger your skull. It can be incorporated into an upper-body muscle-building workout.

How to Do Skull Crusher Lying Triceps Extensions

Verywell / Ben Goldstein

Lie face up on a flat gym bench. Your entire body should be on the bench, except your lower legs. Your knees are bent, and your feet are flat on the floor. Arms extend above the chest, elbows shoulder-width apart (not locked), and both hands hold one end of a dumbbell.

  1. Flex your elbows and lower the weight toward the top of your head. Your upper arms should remain relatively perpendicular to your body. This keeps the tension on the triceps versus shifting it to the shoulders.
  2. Continue lowering the weight behind the head. The bottom of the dumbbell head should be about in line with the bench's top, or even a little higher if this feels unwieldy.
  3. Reverse the movement until the weight is above the chest in the original starting position. Keep from locking the elbow to maintain tension in your triceps muscle.
  4. Repeat.

You can do skull crushers while holding one dumbbell with both hands or, if you want to use more weight, you can hold two dumbbells, one in each hand.

Benefits of Lying Triceps Extensions

The skull crusher is a push exercise that isolates the triceps brachii, working it from the elbow up to the latissimus dorsi muscle of the back. The triceps brachii contains three heads, which you can target by doing various lying triceps extension variations.

You can use this exercise to fix triceps imbalances, for injury rehabilitation, or as part of a bodybuilding routine. We use our triceps for both push and pull motions, so strengthening them makes it easier to perform everyday activities like pushing a loaded grocery cart or pulling sheets up when making the bed.

There are other forms of triceps extensions, such as the overhead extension, which can be an alternative. Both extensions work the triceps similarly. One advantage of the lying triceps extension is that it doesn't place pressure on the wrists.

Other Variations of Lying Triceps Extensions

There are many ways to do this exercise, so you can choose the best lying triceps extension variation for you.

Lying Triceps Extensions on the Floor

If you don't have a weight bench, you can do this exercise on the floor. Just be careful when lowering the weight behind your head. You won't be able to lower it as far without banging it against the floor. If you have an exercise step, you can use that as well.

Barbell Skull Crushers

Some people find it easier to do lying triceps extensions with a barbell rather than a dumbbell. However, using a barbell (even an EZ curl bar) does put more strain on the wrists, so keep this in mind. You may want to strengthen your wrists before using a barbell.

Incline Lying Triceps Extensions

You can also perform skull crushers on an incline bench. This will target different areas of the triceps than when lying flat.

Common Mistakes

Be aware of these common errors so you can avoid them.

Loose Grip

Keep a firm grip to keep the weight from accidentally slipping from your hands and potentially causing damage or injury to your head or face. If this is a concern, you may want to increase your grip strength before performing this exercise.

Lowering Weight Toward the Face

In addition to keeping your grip firm, don't lower the weight toward your face or forehead. Instead, it should travel behind your head. (Also, take care not to hit the back of your head when raising the dumbbell to return to the starting position.)

Hand Position

You can keep your hands about shoulder-width apart during this movement. This helps reduce stress on your elbow joints. However, how you hold the weight depends on your anatomy and preference, so long as no pain or discomfort is felt.

Lifting Too Fast or Sloppily

This exercise should be done slowly and carefully. This makes it easier to keep the weight under good control at all times and can prevent injury. Only move the body parts intended and do not recruit other muscles by using your hips or momentum to move the weight. Doing so will reduce the effectiveness of the exercise.

Too Much Weight and Too Few Reps

This exercise should be done with lower weight and higher reps. It can stress the elbows and a lighter weight helps prevent this. With a lighter weight, you will also be able to keep better form and control.

Safety and Precautions

This exercise can lead to elbow pain. If you have had an elbow injury, such as tennis elbow, it should be avoided. And if you feel elbow pain at any time, end this exercise.

Start with just a few reps of this exercise. As you begin to build strength, work your way up to 3 to 5 sets of lying triceps extensions, each with between 6 and 12 repetitions. If using a barbell, have a spotter available in case you run into difficulty.

Frequently Asked Questions

  • Are skullcrushers good for abs?

    While skull crushers can recruit the abdominal muscles to brace you, they do not target the abs enough to be considered an abdominal exercise. Pullovers, which are similar, will more significantly activate the abdominals.

  • What is the best tricep exercise?

    There is no single best triceps exercise as a variety of exercises will help engage the muscles in different ways. However, some research on muscle activation shows that the triangle push up, kickbacks, and dips activate the most fibers. Keep in mind that these types of studies do not determine the best exercise for your anatomy or goals, such as building muscle size or strength.

  • What is the difference between skull crushers and lying tricep extension?

    A lying triceps extension is the same exercise as skull crushers, by most standards. However, some forms of lying triceps extensions such as the cross-body or single arm are typically called triceps extensions while the double arm version that comes down to the forehead, eyes, or behind the head is often called a skull crusher. The terms can be used interchangeably.

  • Are skull crushers or overhead extensions better?

    Skull crushers and overhead extensions are both excellent triceps movements. You should add both to your programming to target the triceps in different ways, adding new stimulus and volume.

Try It Out

Incorporate this move and similar ones into one of these popular workouts:

7 Sources
Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Boehler B, Porcari JP, Kline D, Hendrix R, Foster C, Anders M. ACE-sponsored research: Best triceps exercises. American Council on Exercise.

  2. Borges E, Mezêncio B, Pinho J, Soncin R, Barbosa J. Resistance training acute session: pectoralis major, latissimus dorsi and triceps brachii electromyographic activityJ Phys Ed Sport. 2018;2018(02):648-653. doi:10.7752/jpes.2018.02095

  3. Kim A. Kinesiology Taping for Rehab and Injury Prevention: An Easy, At-Home Guide for Addressing Common Strains, Pains and Conditions. Ulysses Press, 2016.

  4. Alves D, Matta T, Oliveira L. Effect of shoulder position on triceps brachii heads activity in dumbbell elbow extension exercises. J Spors Med Phys Fitn. 2017;58(9):1247-52. doi:10.23736/s0022-4707.17.06849-9

  5. Sutton B. 9 arm exercises for definition and strength. National Academy of Sports Medicine.

  6. Shuttlewood K, Beazley J, Smith CD. Distal triceps injuries (Including snapping triceps): A systematic review of the literatureWorld J Orthop. 2017;8(6):507-513. doi:10.5312/wjo.v8.i6.507

  7. American Council on Exercise. ACE Study Identifies Best Triceps Exercises.

By Paul Rogers
Paul Rogers is a personal trainer with experience in a wide range of sports, including track, triathlon, marathon, hockey, tennis, and baseball.