The Complete Guide to Your Core Muscles and How to Strengthen Them

What are core muscles, exactly? For one, your core is so much more than just your "abs." Keep reading for a comprehensive breakdown of this crucial muscle group and how to build core strength.

Fit woman doing cross training workout using battle rope. Sportswoman exercising with battle rope on rooftop.
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Contrary to popular belief, your core isn't just your abdominal muscles. In fact, it's a complex group of muscles on your anterior and posterior kinetic chains that all work together to keep you upright, stable, and injury-free while you tackle both everyday activities and workouts.

To help answer all of your burning questions, Shape tapped two fitness experts to break down the primary core muscles and the best exercises to build strength in the entire muscle group. Plus, they reveal why core strength is essential in the first place.

says Laura Miranda, D.P.T., C.S.C.S., a physical therapist in New York City

"If I could change the view of the world on one thing, it's understanding that every single exercise is about your core."

— says Laura Miranda, D.P.T., C.S.C.S., a physical therapist in New York City

Your Core Muscles, Explained

As a whole, your core's primary role is to protect your spine, says Laura Miranda, D.P.T., C.S.C.S., a physical therapist in New York City. "The idea is to control and protect your spine when you're standing erect, moving weights around, and especially when you are hinging, squatting, and bending," they say. The muscles that make up your core don't act solo, either — they all work together to keep your spine stable and prevent injury, they explain. That said, each core muscle has a primary function.

Core Muscle Group: Abdominals

Anatomical diagram of four abdominal core muscles
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Rectus Abdominis

The rectus abdominis muscles are a pair of long, straight muscles that run down the middle of your abdomen, from your ribs to the front of your pelvis. This core muscle is responsible for trunk flexion, or the ability to bend forward or "curl up," according to the American Council on Exercise (ACE). One side of the rectus abdominis also works with the obliques and the erector spinae during lateral trunk flexion, or bending to the side.

Internal and External Obliques

The external oblique muscles are one of the outermost abdominal muscles on your sides, and they run diagonally from the lower half of your ribs down to the pelvis. On the flip side, the internal obliques sit underneath the external obliques and run diagonally from the pelvis up to the lower ribs. Both of these muscles are responsible for rotating your trunk (re: twisting to the left and right) and play a role in lateral trunk flexion, according to ACE.

Transverse Abdominis

The transverse abdominis is the deepest abdominal muscle, and it wraps around the entire waist like a corset to support the spine, says Miranda. This core muscle is responsible for compression of the abdomen, such as when you draw your belly button into your spine, according to ACE. It also helps to create intra-abdominal pressure and provide deep core stability, which prevents hyperextension and overflexion in order to protect your spine, adds Miranda.

Core Muscle Group: Erector Spinae

Anatomical diagram of erector spinae muscle
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The erector spinae is a group of muscles that runs vertically along both sides of the spine. These core muscles, aka the back extensors, allow you to extend your trunk, such as rolling up from a forward fold or bending backward into a bridge, according to ACE. One side of the erector spinaealso works with the obliques and rectus abdominis to allow for lateral trunk flexion. If you were to bend toward your right, for example, the right side of your erector spinae would help create the movement.

Core Muscle Group: Pelvic Floor

Anatomical diagram of pelvic floor muscles
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The pelvic floor is a group of four muscles (including the coccygeus, iliococcygeus, puborectalis, and pubococcygeus) that sits at the bottom of the torso and forms a hammock across the pelvic opening to support the bladder, bowel, uterus, and vagina. Within the core, the pelvic floor also helps provide stability to your spine, says Miranda.

Core Muscle: Diaphragm

Anatomical diagram of female diaphragm
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The diaphragm is a large, dome-shaped muscle that sits at the base of the lungs and contracts and expands as you breathe. In turn, this core muscle plays a key role in creating intra-abdominal pressure, or the stiffness you need to create motion and prevent excessive motion in the spine, says Miranda. Specifically, the diaphragm contracts when you inhale, which increases intra-abdominal pressure and simultaneously contracts the pelvic floor muscles and transverse abdominis, research shows. (This guide breaks down the exact benefits of diaphragmatic breathing for exercise.)

The Importance of Training Your Core Muscles

Your core is at the, well, core, of everyday movements, such as lifting a child out of a crib, twisting to grab a can out of the pantry, and even standing upright. The muscle group is also called upon when you're carrying out lower- or upper-body exercises in the gym, such as squats and tricep presses, says Miranda. "If I could change the view of the world on one thing, it's understanding that every single exercise is about your core," they explain. "Whether you're pressing weight overhead, doing lateral raises, doing something with heavy weights sitting on your body [think: hip thrusts], even though it's a shoulder or leg exercise, your ability to push more weight and do it safely without injuring your lower back is entirely resting on your ability to fire your core appropriately all the way around."

Just think of an overhead press: During this exercise, you'll need to align your ribcage over your pelvis to put your spine in a neutral position, then use your entire core to keep it there while you raise the weights to the ceiling, says Miranda. "Your core is literally in the center, so if it's not strong, you're actually going to have a harder time with the exercise both in form and in the amount of weight you can lift," adds Erica Marcano, M.S., C.S.C.S., a certified athletic trainer in New York City. Without stability coming from your core, you risk excessively arching your lower back to compensate, which, in the long run, can lead to back pain and injury, says Miranda.

What's more, focusing only on one component of your core (think: the rectus abdominis, which creates that "six-pack" look) and ignoring the others (such as your erector spinae) could increase your risk of muscle imbalances, says Marcano. Eventually, the muscles on the weaker side of the body can become more vulnerable to injury while training, and those on the stronger side can suffer an overuse injury, Alena Luciani, M.S., C.S.C.S., the founder of Training2xl, previously told Shape. TL;DR: You rely on your entire core — not just your abdominals — to safely and effectively tackle activities in and out of the gym, and it shouldn't be overlooked.

Expert-Approved Core Muscle Exercises

While you'll train and strengthen your core during most exercises when engaged properly, there are a few core muscle-specific exercises worth incorporating into your fitness routine. The following exercises target specific core muscles, but they'll still strengthen the others, as your entire core works in synergy, says Miranda. As you power through each rep, remember to keep breathing, as your diaphragm plays a key role in engaging your core and providing essential stability.

To (Mainly) Target Your Obliques

The internal and external obliques both create and prevent rotation, so consider exercises that train both, such as lateral medicine ball wall slams, rotational punches with a band or cable, plank pull-throughs with a dumbbell or kettlebell, suggests Miranda. Regardless of the oblique exercises you choose to do, make sure to perform them on both the right and left side of your body.

Lateral Medicine Ball Wall Slam

Laura Miranda, D.P.T., C.S.C.S.

Rotational Punch

Laura Miranda, D.P.T., C.S.C.S.

Plank Pull-Through

Laura Miranda, D.P.T., C.S.C.S.

To (Mainly) Target Your Rectus Abdominis

Instead of a traditional crunch, Miranda recommends performing reverse crunches — slowly driving your knees to your chest — while holding a resistance band above your chest to train this core muscle and minimize neck and back strain. To engage your pelvic floor, squeeze a small exercise ball between the knees, they suggest. You can also use a band or cable to perform Pallof presses, an anti-rotation exercise that trains your rectus abdominis and obliques, they say. To simultaneously fire up your glutes, try a round of kneeling overhead Pallof presses, making sure not to let your lower back arch, says Miranda.

Reverse Crunch with Resistance Band

Laura Miranda, D.P.T., C.S.C.S.

Pallof Press

Laura Miranda, D.P.T., C.S.C.S.

Kneeling Overhead Pallof Press

Laura Miranda, D.P.T., C.S.C.S.

To (Mainly) Target Your Transverse Abdominis

The transverse abdominis is engaged in every single core exercise, but to target this corset-like muscle specifically, lie on your back with both knees bent. Then, bend your right knee as close to your chest as possible, place your left hand on your right knee cap, and press against your leg with all your might for a few seconds. "Your knee is pulling in and your hand is pushing away, and you should feel that side of your core light up," says Miranda. "The harder you push, the more tension is created in the core, in your transverse."

You can also try the classic dead bug exercise, which involves lying on your back and simultaneously extending and lowering your right arm and the left leg toward the floor, then repeat the movement on the opposite sides, says Marcano.

Transverse Abdominis Activation

Laura Miranda, D.P.T., C.S.C.S.

Dead Bug

Laura Miranda, D.P.T., C.S.C.S.

To (Mainly) Target Your Erector Spinae

The bird dog exercise is basically a dead bug performed in a table-top position rather than a supine one, says Marcano. And it's particularly useful for activating the erector spinae and the rectus abdominis, research shows. (FTR, Miranda typically recommends bird dogs and dead bugs solely for beginners who aren't yet sure how to stabilize a neutral spine, and once that stabilization has been mastered, they suggest moving on to the more advanced moves mentioned above. If these two core muscle exercises work for you and you personally enjoy them, though, feel free to keep them in your routine.)

Bird Dog

Laura Miranda, D.P.T., C.S.C.S.

How to Incorporate Core Exercises Into Your Workouts

So, how often should you perform these core muscle exercises? Before kicking off a cardio session or strength-building workout, Marcano suggests powering through a short workout that activates 360 degrees of your core, from your rectus abdominis to your erector spinae. In turn, these muscles will feel awake and ready to support you through your squats or jog, and you'll be able to remember exactly how it feels to engage every one of your core muscles, she says.

When you perform that quick core session, take note of any significant difference in strength right to left or back to front, adds Miranda. If you pick up on any muscle imbalances, do an extra set on the weaker side, they suggest. Those few extra reps may be annoying, but trust, the rest of your workout will only improve.

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