What Muscles Does a Plank Work?

The plank is a classic core exercise, which can be used to develop core strength and muscular endurance. Here, we’ll delve into exactly what muscles the plank works, along with how to adapt the plank to fit your training needs.

What muscles does a plank work?

Planks are considered an isometric exercise, which means you’re essentially holding a single position without moving, with your muscles, particularly the core muscles, continuously working hard to keep you in that one spot (i.e., your muscles contract without changing length). The main muscles working during the plank include the…

  • Transversus abdominals
  • Rectus abdominals
  • External oblique
  • Internal oblique

But, what about the rest of the body? It’s right to say the rest of your body must also work to hold the plank position. While it’s true that muscles like the erector spinae (lower back), trapezius, rhomboids and hip flexor muscles are engaged, they contribute to a much lesser extent compared to the four key core muscles we’ve mentioned.

Transverse abdominals

The transverse abdominal muscles are the deepest muscles within your abdomen, they wrap around the front and side of your abdomen between the bottom of your ribs and top of your pelvis.

They are responsible for holding the lower back, pelvis and torso stable and braced during the plank.

Rectus abdominals

The rectus abdominal muscles run vertically along the front of your abdomen, creating the abs’ distinct “six-pack” appearance.

They are responsible for flexing (bending) your torso forward, so during the plank, their role shifts to resisting the extension (arching) of your torso and spine.

External oblique

The external obliques, also called “the obliques”, are the outermost muscles on the side of your abdomen.

They are responsible for bending the trunk sideways, forwards, backwards, and rotating, so during the plank, they work to resist extension (arching) of your spine and provide stability to the hip and back.

Internal oblique

The internal obliques are also called “the obliques” and line in between the transverse abdominals and external obliques.

Like the external obliques, they are responsible for bending the trunk sideways, forwards, backwards and rotating, so during the plank they work to keep the body in a straight line and provide stability to the hip and back.

Plank muscles worked diagram

A labelled diagram of the muscles worked during a traditional plank
A labelled diagram of the muscles worked during a traditional plank – Image from: https://caliberstrong.com/blog/abdominal-muscles/

Muscles worked for variations of planks

What we’ve covered above are the muscles worked for the traditional plank. Below, we’ll cover some of the most common variations of planks and how they change the muscles that are targeted, plus when and why you might use them:

Plank on the Knees

What are planks on the knees?

Planks on the knees are similar to that of your traditional plank, but instead of having your toes on the ground, you support your body by placing your knees on the ground, keeping your knees and hips in line with shoulders and elbows.

Why do planks on the knees?

Planks on the knees are a great introductory exercise to planks for beginners or for those who need a less intense variation! Placing the knees on the ground reduces the leaver length, reducing the amount of your body weight you must hold.

What muscles does plank on the knees work?

Planks on the knees work the exact same muscles as the traditional plank, including the transversus abdominals, rectus abdominals, external obliques and internal obliques. However, the plank on the knees works these muscles to a lesser extent than the traditional plank.

Straight arm plank

What are straight arm planks?

Straight arm planks are a variation of the plank exercise, where you support your body’s weight on your hands, similar to a push-up position, while keeping your body in a straight line from head to heels.

Why do straight arm planks?

Straight arm planks can improve core strength and muscular endurance just like the traditional plank. Some may also find straight arm planks more comfortable on the shoulder and can be used in preparation for learning a push-up.

What muscles do straight arm planks work?

Straight arm planks work the same muscles as the traditional plank; however, they are more demanding on the shoulder girdle and wrists.

Plank shoulder taps

What are plank shoulder taps?

Plank shoulder taps are performed in a straight arm plank position. Instead of holding this position still, you alternatively tap your hand on the opposite shoulder while keeping your body in a straight line.  

Why do plank shoulder taps?

Plank shoulder taps are a more advanced version of the traditional plank. It is a dynamic exercise that focuses on anti-rotation, or in other words, challenges you to keep your body in a straight line.

What muscles do plank shoulder taps work?

Plank shoulder taps work the same muscles as traditional planks, including the rectus abdominals, transverse abdominals and internal and external obliques. However, they may engage them to a greater extent as it’s a more demanding exercise to maintain the straight line position.

Side plank

What are side planks?

Side planks are a variation of the traditional plank, where you support your body’s weight on one forearm and the side of one foot while lying on your side. Your body forms a straight line from your head to your heels, creating a sideways “plank” shape.

Why do side planks?

Side planks can be used to improve core strength and muscular endurance of the core, particularly the obliques. It can also be used to develop lateral hip stability (i.e. preventing your hips from tilting or swaying), which is important in sports that involve running.

What muscles do side planks work?

The main muscles’ side planks work are the internal and external obliques. The side plank also works the transverse abdominals, rectus abdominals, quadratus lumborum and gluteus medius.

Muscles worked for plank alternatives

Planks serve as an excellent starting point for athletes, but as you progress in your training, it becomes necessary to introduce progressions for continious development of core strength and muscular endurance. In the following section, we’ll delve into a couple of alternative exercises that can be used to progress the traditional plank.

Deadbugs

What are deadbugs?

Deadbugs involve lying on your back and raising your legs so that your keeps are directly above your hips, forming a 90-degree angle with your legs. Then, lower your opposite arm and leg in tandem towards the floor and return to the initial position and perform the same action with your opposite arm and leg, all whilst keeping your back flat on the floor.

Why do deadbugs?

Deadbugs are a great exercise that we programme for most athletes, not only does it strengthen your core, but it also (1) helps athletes practice keeping their lower back flat on the ground (i.e., a neutral pelvic tilt) and (2) trains you to keep your core stiff and stable whilst your limbs are moving.

What muscles do deadbugs work?

Deadbugs work your rectus abdominals, transverse abdominals and internal and external obliques.

Dish (hollow) holds

What are dish (hollow) holds?

Dish holds, also known as hollow holds, involve lying on your back with your arms above your head and legs straight out in front of you. Then, you lift your arms and legs 2-3 inches off the ground and create a “hollow” or “dish” shape with your body, while keeping your back flat.

Why do dish (hollow) holds?

Dish holds can develop strength and muscular endurance in the core, particularly the anterior core muscles like the rectus abdominals and transverse abdominals. Dish holds can help teach athletes to hold positions by maintaining a stiff and stable core.

What muscles does dish (hollow) holds work?

Dish holds work your rectus abdominals, transverse abdominals and internal and external obliques.

Benefits of planks

For athletes, planks offer multiple benefits, including:

  • Teaches athletes to hold positions – planks require you to keep your core stiff and stable, which are important qualities in most sports.  
  • Teaches athletes lumbopelvic stability and control – planks promote awareness of pelvic tilt or positioning to keep the back flat, where athletes learn to avoid excessive anterior pelvic tilt (arching of the lower back) or posterior pelvic tilt (tucking the pelvis under).
  • Simple and equipment-free – planks are relatively easy to learn owing to their relatively low technical demand. They can also be completed anywhere, given that it requires no equipment.  
  • Develop strength and endurance of your core – if performed to the correct sets, reps and intensity, planks can develop strength and/or endurance in the core muscles, including the transverse abdominals, rectus abdominals, external obliques, and internal obliques.
  • Back friendly – planks place relatively low compressive forces upon the spine compared to other core exercises such as crunches and sit-ups, making them safer for your back.

Plank training recommendations

Planks can be used to develop strength and muscular endurance. Here are some guidelines for sets and reps to target these training goals:

Developing strength

If you already have a foundation in strength training, you may incorporate planks for shorter durations (e.g., 10 seconds) with increased resistance, such as using a weighted vest or placing a plate on your back for 3-5 sets.

Developing muscular endurance

For those focusing on muscular endurance, extend the duration of each plank hold (e.g., 20-45 seconds) using your body weight for 2-4 sets.

Other considerations

Safety

It’s key to ensure that all planks are executed with the correct technique! Prioritize mastering the correct posture and maintaining positions before focusing on building strength and muscular endurance.

Progressive overload

Once you’ve mastered the correct technique, it’s important to incorporate progressive overload into your programming to continue developing your strength and muscular endurance.

For those looking to develop strength, consider introducing incremental loads (e.g., 1.25kg) to your sets each week. Conversely, if your goal is to improve muscular endurance, think about adding more sets of increasing the duration each week – ensuring you can maintain the correct form throughout!

Frequently asked questions

Do planks actually build muscle?

Yes, planks can be used to build muscle in your core, particularly the transverse abdominals, rectus abdominals, and internal and external obliques, to some extent. To build muscle, you must apply principles of progressive overload, and you may come to a point where you are no longer challenged by planks, so may need to progress to a more challenging variation or exercise to continue to build muscle in your core.  

What muscles do a side plank work?

The main side plank muscles worked are the internal and external obliques. The side plank also works the transverse abdominals, rectus abdominals, quadratus lumborum and gluteus medius.

Is plank necessary?

It depends, it depends on your training goals and what you’re selecting the exercise for. If you are looking for an introductory core exercise that is simple, equipment free and teaches athletes to hold positions or have lumbopelvic control whilst developing core strength, then the plank is a good option. However, plenty of other core exercises meet those outcomes, including deadbugs and dish (hollow holds).

How many planks should I do?

If you’re aiming to build strength, consider incorporating 3-5 sets of 3-5 planks, each held for 10 seconds. Alternatively, if you are focused on improving muscular endurance, you could consider aiming for 2-4 sets, with each plank held for 20-45 seconds.  

How often should I plank

Aim to plank 2-4 times a week to improve strength or muscular endurance.

Which type of plank is most effective?

This depends on your training goal, as there are various plank variations, each offering specific benefits. For example:

  • If you are aiming to enhance core stability and overall strength, the traditional forearm plank is a solid choice.
  • For those looking to engage obliques and improve lateral core strength, side planks are effective.
  • Plank shoulder taps provide a dynamic core exercise that challenges you to maintain core stiffness and stability while your arms are moving.

Is side plank harder than plank?

Side planks are often considered more challenging than the traditional plank, given that you must balance your body on one arm and foot, which is a less stable base of support when compared to the traditional plank, where you are supported by two feet and arms.

Summary

Planks are effective for developing core strength and muscular endurance, targeting muscles including the transverse abdominals, rectus abdominals, and both internal and external obliques.

There are a number of variations and alternatives to the traditional plank, which can target your core muscles in a slightly different way to meet your training goals.

Happy planking

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Emily, co-founder of Sport Science Insider, graduated from the University of Leeds in 2020 and went on to become an accredited S&C coach with the UKSCA in 2022. A former athlete herself, Emily has since gone on to deliver S&C coaching for the Southern Academy of Sport, GB Rowing, GB Taekwondo and works currently as a full-time S&C coach at the University of Leeds.