How to Do Lying Triceps Extensions: Proper Form, Variations, and Common Mistakes

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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.

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

Targets: Triceps

Equipment Needed: Dumbbells (or barbell), weight bench

Level: Intermediate

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 are extended above the chest, elbows shoulder-width apart (not locked), and both hands are holding one end of a dumbbell.

  1. Flex your elbows and lower the weight down 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 all the way up to the latissimus dorsi muscle of the back. The triceps brachii contains three heads. which can be targeted by doing a variety of lying triceps extension variations.

This exercise can be used 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

Keep your hands about shoulder-width apart during this movement. This helps reduce stress on your elbow joints.

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.

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.

Try It Out

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

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6 Sources
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