You are familiar with the sensation when you are reclining in bed, using your mobile device, elevating it above your face, and experiencing fatigue in your arms? Well, you are essentially engaging in a skull crusher exercise – a triceps workout that can result in impressive arm muscles and enhance your performance at the gym.

In the following sections, fitness experts will thoroughly explain all the essential details regarding this exercise that helps build strength. This includes instructions on how to properly execute skull crushers, how to modify and advance the movement based on your individual requirements, and how to incorporate it into your workout routine. Believe us, skull crushers not only have an imposing name, but they also instill a sense of empowerment.

Executing Skull Crushers

Skull crushers, also known as lying triceps extensions, are typically performed while lying on a bench using one or a pair of dumbbells. In this position, you hold the weights above your face (hence the name “skull crusher”) with your elbows pointing upward. You then engage your triceps (the muscles on the back of your upper arm) to extend your elbow and raise the weights towards the ceiling.

However, it’s not just your triceps that receive a workout during this exercise. According to Ash Wilking, a Nike master trainer and Tonal coach, utilizing a bench allows for engagement of different muscle groups in your lower body and core. By activating your glutes, maintaining a tucked pelvis, and keeping your core contracted while keeping your rib cage down, you apply conscious effort throughout the exercise.

If you need assistance envisioning proper technique, you can observe Dannah Bollig, an ISSA-certified personal trainer and the creator of The DE Method, as she demonstrates the execution of skull crushers below. It is important to note that you should keep your elbows tucked in and shoulder-width apart, while ensuring that your back remains flat against the bench.

A. Secure a dumbbell in each hand and position yourself facing upward on a bench, with your feet resting flat on the ground on each side of the bench.

B. Extend your arms towards the ceiling above your chest, with your palms facing each other. Engage your glutes and core muscles, while pulling your rib cage downward to prevent excessive arching of the lower back.

C. Contract your elbows inward and press your shoulders downward. Gradually lower the dumbbells by bending your elbows until they hover approximately an inch above your head or at either side of your head.

Prevent relocating higher appendages and fasten shoulders downwards to activate the latissimus dorsi muscles, isolating the triceps as the weights descend.

D. With control, extend arms back over chest by straightening elbows.

The Main Benefits of Skull Crushers

Developing triceps strength is not the sole advantage of skull crushers. Here, you will find all the advantages that come with incorporating skull crushers into your workout routine.

Isolates the Triceps

Skull crushers are a workout that isolates a specific muscle group, which means you only use one joint (in this case, the elbow) during the exercise. As a result, you primarily rely on the triceps to complete the movement, allowing you to effectively target these smaller arm muscles. This is something that is difficult to achieve with other upper body exercises. “The triceps rarely take the lead, in comparison with biceps for lifting or holding, or glutes for walking or standing,” says Wilking. “In other words, they assist larger muscle groups in performing countless movements both in strength training and everyday activity,” she adds.

Enhances Performance in Upper-Body Exercises

“The triceps contribute to your overall pushing strength and are the primary extensors of the elbow joint,” explains Riley O’Donnell, a NASM-certified personal trainer and instructor at Fhitting Room in New York City. “So if you’re looking to improve your performance in overhead presses, chest/bench presses, or push-ups, strengthening your triceps will help you achieve your goals.”

Specifically, skull crushers enhance pushing movements by training your body to handle weight with your elbows in a bent position and then extending your arms to a locked-out position, explains O’Donnell. “When we push things, we not only engage our shoulders, chest, and core, but we also need to be able to extend the elbow powerfully,” she says. So if you’ve been having difficulty with push-ups, practicing skull crushers can make this bodyweight exercise feel more manageable.

Provides a Low-Impact, Injury-Friendly Workout

By solely engaging the elbow joint, skull crushers isolate the triceps, which is not the case for many other exercises that primarily target the triceps, says O’Donnell. “For instance, standing triceps extensions and triceps dips require shoulder mobility that not everyone possesses,” she explains.

Due to this, skull crushers are most appropriate for individuals who have a restricted scope of movement in the shoulders and desire to enhance the strength of their triceps.

Enhances Grip Strength

Skull crushers also have a significant impact on improving grip strength, which is necessary to prevent accidental weight dropping and literal head crushing. However, in real life, grip strength is crucial for effortlessly performing everyday tasks like carrying groceries or opening jars of pickles. “When executing skull crushers, whether with dumbbells, a barbell, or a plate, it’s important to maintain proper wrist alignment. It can be tempting to bend the wrist during this movement because it feels easier to hold the weight, but focusing on maintaining straight wrists enhances grip strength,” says O’Donnell. (Need more grip strength training? Give this battle rope workout a try.)

Muscles Targeted by Skull Crushers

As mentioned earlier, the triceps brachii is the primary muscle engaged (also called the agonist muscle group) during the isolated skull crusher exercise. Its main function is to extend the elbow, but it also provides stability when utilizing the hands and forearm muscles for precise movements (such as writing), according to research. Furthermore, the exercise also targets the muscles in the fingers, hands, and forearms, which contribute to grip strength.

Variations of Skull Crushers

If you find that the classic skull crusher exercise doesn’t align with your fitness level or personal requirements, do not worry. The following modification and progression ideas will assist you in customizing the exercise to meet your specific goals and needs.

Modification: Skull Crushers On a Mat

The best way to modify skull crushers is to perform them on the floor instead of a bench. Keep your knees bent and hold a single lightweight dumbbell with both hands, recommends Bollig, who demonstrates the exercise below. “This allows for a shorter range of motion and provides a safe stopping point (the floor),” she explains. “Additionally, it gives you complete control over the movement since you’re using a single weight held in both hands.” While your range of motion may be slightly limited, this adjustment will help you develop proper form, says Chris Pabon, a NASM-certified personal trainer and fitness manager at Blink Fitness.

Moreover, this variation of skull crushers offers its own unique benefits. Your knees are more bent compared to the traditional version, allowing you to tilt your pelvis and establish a stronger connection with your rib cage, notes Wilking. “This connection restricts shoulder movement and truly isolates the triceps,” she explains.

Once the weight you are using no longer poses a challenge, you can perform numerous repetitions effortlessly, or if you have mastered the form while doing skull crushers on the floor, you may consider progressing to the traditional skull crusher exercise, advises Bollig.

Progression: Increase and Decrease Skull Crushers

If you’re seeking to enhance the skull crusher exercise, consider adjusting the incline of your bench. Altering the slope on the bench can target specific sections of the triceps more intensively than others, states Pabon. For instance, utilizing a decline bench (with your head positioned lower than your feet) will activate the lateral tricep head, located on the outer side of your arm, to a greater extent. On the other hand, performing the exercise on an incline (with your head elevated) will primarily work the long head of your triceps, situated on the inner side of your arm, starting just beneath the armpit and extending down to the elbow, adds Bollig.

Regardless of which variation you choose, it is crucial to ensure the stability of your bench and establish a strong mind-muscle connection, advises Bollig. “Having a clear understanding of your target muscles and where you should experience a more intense burn will enable you to maximize the effectiveness of the exercises,” she explains. If you decide to increase the weight, it may be wise to have a spotter nearby in case you are unable to complete the lift, suggests Bollig.

Common Skull Crusher Errors

Although skull crushers are not overly complex to master, they can lead to injuries and discomfort if performed incorrectly.

The primary mistake to avoid is flaring out your elbows in an attempt to make the exercise easier on your triceps. “It is crucial to keep your elbows tucked in, approximately shoulder-width apart, directly behind your wrists,” advises Bollig. “This not only protects your joints and ligaments but also ensures proper muscle targeting.”

For a visual guide, “imagine that your elbows are embracing a balloon to prevent flaring and visualize your upper arms against a wall throughout the entire movement,” suggests O’Donnell. This will assist in maintaining a stable upper body on the mat or bench. Alternatively, you can envision grasping a steering wheel and turning your pinky fingers downward and inward to engage the lats, recommends Wilking.

Equally important is avoiding shoulder shrugging. To fully isolate the triceps and avoid utilizing the shoulders or upper arms, depress your shoulders or engage the lats, according to O’Donnell. “When the lats are not engaged, there is a tendency for the upper arm to move during the skull crusher,” explains O’Donnell. Engaging your core can also aid in stabilizing the upper body, she adds. “Since the skull crusher is performed while lying on your back, your core works to keep the ribcage aligned throughout the movement and ensures the lower back remains in contact with the floor or bench,” she explains. Aligning the rib cage involves pulling it downward and together, activating the deep core muscles to prevent compression of the lower back.

Throughout the movement, ensure that your back remains stuck to the bench or ground; arching increases strain on the lower back, which can result in discomfort and injury. To prevent the arching of the lower back, make sure to select a weight that is not overly heavy, according to Bollig. (The weight should be light enough for you to perform 10 to 12 repetitions with proper form, but the last few reps should be slightly challenging.) Moreover, always remember to pull your rib cage down towards the floor, as suggested by Wilking. “Think about exerting maximum pressure on the ground with your feet and leveling your rib cage while pressing the back of your ribs against the floor or bench,” advises O’Donnell.

Lastly, execute the movement with slow and controlled motions. “Control the weight in both directions — during the eccentric (lowering) and concentric (pressing) phases of the movement. Injuries usually occur during deceleration and/or rotation, so focusing on controlling the weight is crucial,” states Pabon.

Incorporating Skull Crushers into Your Workout Routine

Prior to picking up a pair of dumbbells and attempting a set of skull crushers, make sure to receive approval from your healthcare provider if you are new to the gym or have any existing injuries or health concerns, according to Bollig.

If you are given the go-ahead, beginners should typically start by holding only one lightweight dumbbell (such as a 10- or 12-pound dumbbell) with both hands, says Bollig. “It is much easier to control a single dumbbell because you are only guiding one weight instead of two, which requires more muscle control and coordination,” she explains. Once you master the exercise, you can increase the weight or try holding one dumbbell in each hand, she suggests.

If you have access to a well-equipped gym, you can even perform skull crushers using an EZ curl bar — a weightlifting bar with a distinctive “W” shape. The technique is generally the same, although you may be able to lift heavier weights compared to using dumbbells (as dumbbells are slightly more challenging to control), according to Pabon. Additionally, the EZ bar can help keep your elbows tucked in, he adds.

Regardless of the chosen weight, starting with three to four sets of 10 to 12 reps is a good initial approach. Consider incorporating skull crushers into your workout routine on days when you focus on other “push” muscles, such as the chest or shoulders, advises Pabon. “It is an excellent way to effectively target and engage the triceps after they have been utilized as secondary muscles during the initial part of the workout,” he notes. For an extra challenge, attempt performing skull crushers in a superset workout with a biceps exercise on arm days, as suggested by Wilking.

Alternatively, you can utilize skull crushers as an active recovery movement.

For instance, if you’re engaging in a leg or comprehensive physique exercise, employ skull crushers while giving your legs time to recuperate between sets,” states Wilking. Irrespective of how you incorporate the workout into your regimen, your triceps will definitely express gratitude for it.