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If you want to develop an upper body exercise routine that helps you build stronger triceps and bigger arms, consider incorporating skull crushers.

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What Is a Skull Crusher?

A skull crusher, also known as a lying triceps extension, is an isolation exercise focused on your triceps muscles. Skull crushers are performed by lying on your back on a flat bench and lifting dumbbells from behind your head to full extension above you. With proper form, this strength training exercise can be more than just a triceps exercise—it can also work muscle groups like the deltoids in your shoulders and the latissimus dorsi muscle in your back. Some skull crusher variations substitute dumbbells for a barbell or a pair of kettlebells.

Skull Crusher vs. French Press: What’s the Difference?

The main difference between the skull crusher and the French press is the starting position and posture. While you do skull crushers lying on your back, you do French presses while standing. French presses typically use a specific kind of barbell with an angled grip called an EZ curl bar. An EZ bar French press allows for a greater range of motion than a traditional skull crusher. Both exercises serve as helpful warm-ups for other bodybuilding workouts like the close-grip barbell press, bench press, or deadlift.

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How to Do a Skull Crusher

For the skull crusher, begin by using a weight that you can control for 2–3 sets of 10-12 repetitions. Choose a weight that allows you to maintain good technique throughout all sets and repetitions. When you’re learning the exercise, start with lighter weights and lift with a spotter.

  1. Life face-up on a bench or an exercise mat, and hold a pair of dumbbells—one on either side of your head. Your feet should be in contact with the floor.
  2. Keep your core engaged throughout the duration of the entire exercise set.
  3. Push the dumbbells toward the ceiling, and rotate your shoulders outward until your inner elbows point toward your face and your outer elbow joints point away from you. You should feel tension in your lats, which will help maintain optimal shoulder and arm positioning. Your chin should remain tucked throughout the movement, as if you were holding an egg under your chin. All repetitions should start from this position.
  4. While keeping your upper arm still, bend your elbows, and allow the dumbbells to travel toward your head.
  5. With control, lower the dumbbells down to the sides of your head.
  6. Pause for a second in the bottom position.
  7. To complete the repetition, squeeze your triceps and straighten your elbows until you’ve reached the starting position. Your elbows should be slightly bent at the end of the repetition in order to keep tension on the triceps.