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The skull crusher is a superb exercise for targeting the triceps (tricep brachii), that three-headed muscle running the upper back of each arm. And, comprising over half the muscles in your arms, it's no wonder triceps are an important muscle group. Whether it's increasing your strength and muscle aesthetic to improving shoulder stability and promoting enhanced synergy between other upper body muscles, make sure to give your triceps some love on the gym floor!
Given the precarious position in which the weight is held, you can imagine where its name stemmed. But fear not, with proper execution, the skull crusher is a safe and very effective exercise.
Below, experts share how to perform a skull crusher.
Meet the Expert
- Laura Flynn Endres is a personal trainer and the founder of the online team fitness game, Get Fit Done.
- Dayna Douglas Hunt is a former Olympic athletic therapist and strength and conditioning coach.
How To Perform A Skull Crusher
The skull crusher requires a few pieces of equipment, including dumbbells or a barbell, as well as a bench, although a floor mat will also do the trick.
Personal trainer Laura Flynn Endres breaks down how to correctly perform a skull crusher:
- Grab two dumbbells of choice and lie face up on a bench or the floor
- Extend your arms toward the ceiling with palms facing inward and the dumbbell shaft vertical
- Ensure your upper arms are not moving back and forth as during (to avoid loading the shoulders) as you flex your elbows and lower the dumbbells down. Exhale here
- Continue this phase with control until the dumbbells reach just behind your ears
- Begin to reverse this movement by straightening your arms and pushing the dumbbells back up to the starting position. Make sure not to lock your elbows at the top.
Olympic athletic therapist and strength and conditioning coach Dayna Douglas Hunt offers some key tips to protect your form. “Keep a neutral spine throughout, and if you are lying on the mat, make sure your feet are flat, and your knees are bent.” She also stresses holding your elbows tight and pointing them toward the sky to bring the elbow and shoulder perpendicular. “You want to keep your elbows and shoulders still so that your weight, wrist, elbow, and shoulder are in line.” Another consideration is to slowly lower the weight back down with control to feel the contraction at the back of your arms.
Be mindful of the elbows wandering away from the body, lowering the weight to your forehead (more relevant with a barbell) rather than behind your head, and performing the motion too quickly without proper muscle control.
What Muscles Are Worked
As previously explained, skull crushers are a single-joint exercise isolating the triceps. “They’re also a “push” exercise and are therefore suitable for workouts in push-pull programs, and also work as an opposing muscle group exercise if you’re working on the biceps, for example,” says Flynn Endres. Of course, the core, which stabilizes the body and prevents the back from arching, plays a role in executing the skull crusher properly.
“Aside from including in a push/pull day, skull crushers fit perfectly into an upper-body routine and also on compound days as an accessory or a burnout movement,” says Douglas Hunt.
Modifications and Variations
First, practice perfecting the movement before loading on the weight. You can also loop a resistance band around your wrists to create some tension without a heavy load. Once you understand the movement, Flynn Andres suggests switching to dumbbells and working up to 15 reps with control. "At this point, you can increase the weight." Another tip - hold one dumbbell with both hands by the bell to ensure both arms work together and lower the shaft past the forehead. This provides a more secure group for those who feel shaky, starting with two dumbbells.
- Use an EZ curl bar designed to isolate the triceps and biceps. The same as using one dumbbell, the bar will lower toward your forehead, so work within a safe range.
- Use a cable rope in place of weights, maintain a neutral grip to alter how the triceps work. Turn the palms down at the top of the movement and hold for a second to really feel the muscles contract at the top of this movement.
- To relieve pressure on the wrists, alter to a reverse grip with an EZ bar and perform the same movement with your palms facing up.
- Perform on an incline bench to recruit more of the muscle fibers on the long head muscle
- Overhead extensions allow you to deepen the motion of the exercise to recruit even more of the muscle.
- Tricep cable pushdowns are an effective variation for elbow pain as they reduce some of the pressure.
Who Should Avoid Them
Before attempting a skull crusher, there are a few contradictions to consider. “As the name suggests, skull crushers require a good bit of control to actually avoid crushing your skull, and so I prefer for my clients to start with light weights to be sure they can control the eccentric (lowering) portion of the exercise,” explains Flynn Endres. “If you feel unstable at all, it’s safer to start with tricep exercises like kickbacks with a band.” Also, if you have a strength discrepancy between each arm, using two dumbbells for this exercise might not be the safest option.
"Skull crushers also put a lot of strain and stress on the elbows, so these should be avoided if you are dealing with pain or tendonitis of the elbow,” cautions Douglas Hunt. “You're also putting a lot of stress on the grip of your wrist, so be mindful if your wrists are in pain.”
Skull crushers are a single-joint exercise designed to isolate the triceps and are popular as part of an upper-body or push/pull routine. The exercise is typically done on a bench but can also be performed on a mat using either dumbbells or a barbell. Form is key to ensure your safety and precision in execution, and you should pay particular attention to maintaining a neutral spine and holding the elbows in toward the body. Given that stability and control are required throughout this movement, skull crushers should be slowly built up before adding heavy weights. Skull crushers can also aggravate existing elbow and wrist pain, and a modification or variation of the exercise may be a safer option.