Skull crushers, also called the French extension, French press, or the lying triceps extension is an isolation exercise building the triceps muscle group. Why skull crushers? The movement places your skull in a slightly precarious position, but if done in the correct form with the load that you can handle, it effectively isolates your triceps.

Sure, you’ll get pumped-up arms with regular biceps curls, but if you want to get real results, you cannot ignore your triceps, which require a wider range of exercise.  

This Skull Crusher is a fantastic way to add more mass and definition to the back of the arms. It’s a great move to include in upper-body workout routines as it targets the triceps and tones the arms. Furthermore, it can improve shoulder stability.

Let’s delve deeper into the skull crushers, what they are, the muscles worked, their benefits, a step-by-step guide, and other alternatives or modifications.

How to Do Skull Crushers

What You’ll Need

To perform skull crushers, you will need the following tools:

  • Dumbbells – This will be your added weight, though you can also use your bodyweight or barbell.
  • A flat bench – You can also perform the exercise on the floor.

Step 1. Set Up Your Starting Position

Prepare your position by lying face-up on a flat bench. Your whole body must be on the bench other than your lower legs. You must bend the knees and feet flat on the ground; you should extend your arms above your chest and elbows shoulder-width apart and not locked. Both of your hands should hold one end of a dumbbell at a comfortable weight.

Step 2. Lower Your Dumbbell

Flex your elbows as you lower the dumbbell down to the top of your head. Your upper arms should be perpendicular to your body. That way, you retain tension on your triceps rather than shift the weight on your shoulders.

Step 3. Complete the Low Phase and Hold

Continue lowering the dumbbell’s weight behind your head. The bottom of your dumbbell’s head should be almost parallel with the bench’s top. If the weight feels too heavy, the dumbbell head can be a bit higher. Hold this for about one or two seconds.

Step 4. Go Back to Starting Position

Reverse this movement until your dumbbell weight is back to the exercise’s starting position above your chest. Avoid locking your elbows to maintain tension in the triceps muscles. Repeat the exercise. 

Skull Crushers Benefits

Improve Bench Bress Strength

A study from 2020 showed that performing targeted triceps exercises helped with bench press strength. Skull crushers are one of the exercises that help with that. The triceps will work with your anterior deltoids and pectorals as you perform skull crushers, pushing the weight up and controlling it as you slowly lower your arms.

Activate Your Triceps

Lying triceps extensions are great exercises to activate the triceps’ medial head, compared to standing triceps extensions and exercises where the upper arms are by your side. Furthermore, lying triceps extensions can add mass to the triceps, an essential benefit for bodybuilders. 

Alternative to Overhead Training Exercises

Skull crushers are an effective alternative to the standing overhead triceps extension if you have difficulty with overhead training. It may be easier on the wrists as you can vary the angle of forearm rotation, decreasing any stress. However, you can add more challenge to this exercise by working both sides equally while maintaining core stability.

Develop Force Production

The triceps are involved in straightening and extending our elbows. It’s commonly used in throwing activities like baseball and football. Because of that, lying triceps extensions can help people develop better force production to improve their throwing muscles for overhead throwing movements.

When you have stronger triceps, everyday activities and certain sports become easier. People who incorporate this exercise into their workout will find it easier throwing a baseball or football, pushing heavy shopping carts, or pulling heavy doors open. Skull crushers are a favored exercise since they don’t put much pressure on the wrists.

Improve Your Performance In Lift Competitions

The triceps are the biggest muscle on our arms, making it important to work out to grow muscles. They are also responsible for elbow extension and overhead stability, which are important during competitions’ snatch and jerk parts. When increasing your tricep training with single-joint exercises, you get to build the raw strength and muscle mass required for locking out lifts.

Common Mistakes to Avoid When Doing Skull Crushers

Besides learning the proper form of lying triceps extensions, there are common mistakes to avoid, such as:

  • Flailing Elbows. You need to keep your elbows close and fixed at the same position throughout the exercise. We see too many lifters allowing their elbows to move up, down, or to the sides of their bodies, which is not the proper form.
  • Going Too Fast. Like other tricep exercises, you need to perform the skull crusher slowly and carefully. That way, you can easily control the weight to prevent injuries. Furthermore, you achieve strong triceps and bigger arms through hypertrophy, demanding time under tension. Going too quick won’t work your muscles the way you expect them to.
  • Using Heavier Weights. More weight is excellent, but not when you can’t handle it. Start with a lighter weight or even doing the bodyweight variation. Remember, skull crushers will place a lot of stress on your wrists and elbows, and you don’t want to injure them from going too heavy too soon. Build up your strength and muscle mass over time for stronger triceps, which will eventually handle heavier weight. 
  • Loose Grip. Make sure you maintain a firm grip, preventing the dumbbells from slipping from your hands and causing injuries to your face or head. If you aren’t confident with your grip, it’s essential to increase grip strength before performing the skull crusher. 
  • Lowering the Weight Wrong. Besides maintaining a firm grip, do not lower the dumbbell toward your forehead or face, resulting in injuries. The weight must travel behind the head. While doing the exercise, be wary and avoid hitting the back of your head as you raise the weight back to starting position. 
  • Poor Hand Position. Reduce stress on the elbow joints by keeping the hands shoulder-width apart as you perform the skull crusher. Doing that prevents elbow pain and injury.

Skull Crushers Muscles Worked

  • Triceps: The muscle located on the back of our upper arm. It’s a muscle with three heads, with the long head originating above our shoulder joining on the scapula, called the shoulder blades. Skull crushers will isolate the triceps by performing deep elbow flexion as you stabilize the wrists and shoulder joints.

  • Medial and lateral heads: These are part of the triceps, which originate at the back of our upper humerus, ending at the bony point of the back of our elbows, known as the olecranon. 

  • Shoulder stabilizers: The muscles stabilize the shoulder joints as you perform the exercise. Scapular stabilizers and rear deltoids work hard to stabilize your shoulder sockets, so you stay in a fixed position. 
  • Core muscles: The core will stabilize the body and prevent your back from arching.

Skull Crushers vs. Overhead Tricep Extensions

While skull crushers and overhead tricep extensions are similar exercises, they have key differences. You would perform skull crushers lying on your back on a bench, lifting a dumbbell behind your head to full extension above you. 

On the other hand, the overhead tricep extension is a standing exercise. Skull crushers would activate all three heads of the triceps, while overhead tricep extensions focus on the triceps’ long head.

Our Trainer’s Suggested Set and Programs

To Build Muscle Mass

For bodybuilders who want bigger arm muscles, skull crushers are a good exercise to add to your routine. You can incorporate skull crushers into your workout if you want to build arm muscle mass, particularly in that three-headed muscle. It’s also great to do when you want to tone your upper body or if you just came back from an arm injury. To build your muscles, go for 4 to 6 sets of 8 to 12 repetitions with a moderate load, resting 1-2 minutes per set. 

For Strength Training

To incorporate skull crushers into your strength training routine, go for 4 to 6 sets of 4 to 8 repetitions each, resting for 2-3 minutes per set. You will need to do a heavier load for this, with the aim of lifting heavier but having a longer rest time. That way, you get to overload the triceps while engaging the central nervous system so you can lift even heavier in time.

For Better Muscle Endurance

If you want to build muscle endurance, opt to perform 3 sets of 20 repetitions, resting for 60-90 seconds between sets. Use a slightly lighter load that can have your muscles handle that many repetitions. Some lifters might want to improve their muscle endurance for sports, so higher repetitions with shorter rest periods are required here.

Skull Crusher Variations

If you’re having difficulty performing skull crushers, these are the variations you can do:

Barbell Triceps Extension

This is almost the exact exercise as skull crushers, but this time, you’ll use barbells (regular or EZ curl bar) instead of dumbbells. This is useful when you want to add even heavier weight to the skull crusher. Like the dumbbell skull crusher, begin with low weight, working on perfecting form first. You can start increasing your weight as you become more familiar with the exercise. 

Resistance Band Skull Crusher

The resistance band skull crusher offers better resistance during the start and end phases, particularly when the elbows are most extended. Instead of using dumbbells, you will use a resistance band, which can be challenging to maintain enough resistance as you perform the exercise. You can perform the resistance band skull crusher on a bench, but you can do it on the floor, too.

Bodyweight Skull Crushers

If you have no equipment or want to start without it yet, then this exercise is suitable to start with. Set yourself up in a plank position with hands together. Contract your triceps as you push your body off the ground. Go back to the plank position, then repeat the exercise.

Assisted Bodyweight Skull Crushers

If bodyweight skull crushers are too challenging (for now), you can drop to your knees. The assisted setup removes instability in the lower body while decreasing the amount of weight you push off the floor. Modify this exercise by explosively coming off the floor when you’re on the top of the rep, which builds enough strength to transition to the bodyweight skull crusher.

One-Arm Skull Crusher

Take advantage of the skull crusher by training your arms individually with one dumbbell. This exercise can fix potential arm muscle imbalances. Go for the same position as the typical skull crusher, this time holding your dumbbell with only one hand. Make sure your core stays engaged for strength and stability. 

Skull Crusher Alternatives

If you want to further work on your triceps, there are other exercises you can do for upper body training. Here are our recommended Alternative Exercises for their effectiveness in training the upper arm!

Alternating Triceps Pushdown

This is a powerful isolation exercise for your triceps. Using the pulley cable machine, keep the elbows tucked to your sides as you contact the triceps when at the bottom of the rep.

Overhead Triceps Extension

This exercise will strengthen your triceps’ long head. When extending upwards, pull your rope apart, contracting the triceps at the top of the rep. You can perform this exercise with an EZ bar, dumbbell, or cable machine.

Close Grip Bench Presses

This bench press variation will engage the triceps more than your typical bench press. For the close grip bench press, you’ll need to narrow the grip width on your barbell, tucking your elbows into the sides. Bring the barbell weight down below your chest, contracting your tricep as you press upwards. 

Bench Rolling Triceps Extension

The bench rolling triceps extension is a multijoint exercise allowing you to extend the triceps all the way back and beyond the head, extending the triceps’ long head. Make sure your elbows are in and at the sides of your head as you perform the exercise.

Tricep Dips

Tricep dips are great for muscle mass building that work the triceps, front shoulders, and chest. You can perform this exercise with a dipping belt for added weight, or start with your own body weight.

Wrap Up

Don’t let the name of skull crushers scare you! As long as you learn how to do skull crushers properly with good mechanics, you can perform the exercise safely with less risk of injuries. Skull crushers isolate the triceps, a vital muscle to work on for building strength, arm muscle definition, and muscle mass to perform daily activities with ease. 

There are different variations to perform to begin your journey to mastering the skull crusher and handling heavier weights. That way, you have more control over incorporating this exercise into your current workout routine. For exercise professionals, those beginning their journey with a personal trainer or doing workouts solo, this is an exercise you’ll want to add to your routine.

Frequently Asked Questions

We recommend performing skull crushers early into your upper body training workout. You can load up your skull crusher with more weight, so you won’t rob yourself of the opportunity to lift heavier if you pre-fatigue the muscles with other exercises. 

If you experience any pain, we recommend consulting with a doctor, as this may come from an injury or strain. We suggest steering clear skull crushers first and performing other variations, such as pushdowns. These exercises feel easier on the shoulder joints and elbows.

Skull crushers will work the muscles from the back of the upper arm, starting from the elbows to the lats. It’s an accessory movement that increases tricep strength and hypertrophy while increasing injury resistance for elbows.

While skull crushers aren’t as functional compared to other pressing movements like tricep dips or pushups, this exercise is excellent for those who want to increase their tricep training volume without wearing and tearing their chest and shoulders.

Yes, you can go heavy on skull crushers and do fewer sets and repetitions to build muscle mass. However, don’t go overboard, as this can cause elbow pain during the exercise’s lowering phase.

Barbells are not necessarily better (or worse) than one or two dumbbells, with the goal of skull crushers to work on the target muscle as effectively as possible. 

If you feel the muscles working, then it is but if not, you’ll need to go for a slightly heavier weight, different weight type, or another exercise. You have more freedom, so experiment with what works best for your body and routine.

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