Everything You Need to Know About Your Abdominal Muscles

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If you hear the phrase “strong core” and instantly think of defined ab muscles, you’re not alone. “When talking about our core we often focus on the parts that we can see or have been told by society indicate a strong belly, aka, the rectus abdominis or ‘six-pack’ muscle, says Kristin Leal, a New York-based yoga teacher and the author of MetaAnatomy.

But your core comprises your entire central structure, including all of the abdominal muscles plus the muscles in your back and pelvis. Together they support your spine and keep your body stable and balanced in any situation.

Throughout your day, your abs are nearly always “on” during typical movement, whether you’re doing yoga, sitting, squatting, or just walking to the mailbox—not just when you’re holding Crow Pose or coming into Boat Pose, says Ariele Foster, a physical therapist and yoga teacher based in Washington D.C.

Anatomy of the Abdominal Muscles

There are four main abdominal muscles, says Richelle Ricard, yoga teacher and author of The Yoga Engineer’s Manual.

• Rectus abdominis: A pair of long muscles that run from the sternum to the pubic bone, these allow you to flex forward. The appearance of a “six-pack” or “eight pack” comes from tendinous bands (inscriptions) that cross the muscles at intervals.
• Transversus abdominis: This is your deepest ab muscle, which wraps around the waist to stabilize and support the spine.
• Internal and External Obliques: Inner obliques run diagonally up your sides; outer (external) obliques slant down towards your public bone. Muscles that run in opposing directions such as the obliques work against each other to stabilize your lumbar spine, Ricard says. These muscles  help you flex at your hips, bend to the side, and twist. They also help with exhalation.

How Your Ab Muscles Support the Entire Body

The big rule in anatomy is that everything is connected, explains Leal.

“Conceptually, we don’t usually think of the abdominals as spinal muscles,” Ricard says. But the transversus abdominis and internal and external oblique muscles connect to the lumbar spine and fascia. They help stabilize your movement, hold your abdominal organs, and support the curvature of the spine.”

In whole body movement—including most yoga poses—the entire body has to work in coordination. This is especially true of the abdominals, explains Foster.

“Abdominals need to work in conjunction with the diaphragm for respiratory health; with the pelvic floor for stabilization of your hips, as well as bladder control and urinary health; and with the multifidus muscles, which stabilize the lumbar spine to create a stable trunk,” she says. If one of those structures is dysfunctional, or not doing its part, it’s like a group project with lopsided effort, Foster adds.

Yoga Poses That Activate All of Your Abdominal Muscles

We most often think of the core in poses such as Crow, Boat or Plank, but they are also activated in more gentle poses such as Cat and Cow. Below we take a look at three unexpected yoga poses and how they engage your abdominal muscles.

Extended Triangle Pose (Utthita Trikonasana)

Triangle doesn’t usually make it on lists of ab-focused asanas (poses). But all of the abdominal layers are in play here. “Triangle is a very complex pose when you look at what needs to contract and where,” says Ricard.

In Triangle, the obliques work to maintain balance as you bend to the side and, at the same time, they rotate the spine to help your body achieve that broad, open, stacked-rib form and function. For most people, the hips will not fully face the side in Trikonasana—not without taking your front knee with you, Ricard says. “So, to have the broad open chest this posture is known for, the thoracic spine needs to twist.” The obliques also assist with this.

Meanwhile, the transverse abdominis and the rectus abdominis help you maintain a neutral spine, she says. The upper rectus abdominis contracts to keep the front ribs pulled toward the navel, while the lower rectus abdominis contracts to help the transverse abdominis compress the lower abdomen and provide resistance to the lumbar muscles.

There can be a tendency in this pose to sink your weight into your bottom hand on your shin or a block. Instead, Leal suggests first reaching your bottom arm out toward the front of your mat. This forces your obliques to work antagonistically—one contracts and one stretches—to create length in your waist. Once you have this feeling, then bring your hand down lightly to your shin or a block.

When you come out of the pose, you once again rely on your obliques to pull yourself back up to standing.

Revolved Chair Pose (Parivrtta Utkatasana)

“Closed twists or poses that rotate your torso inward, like Revolved Chair Pose and Revolved Crescent Lunge, can also target the whole core,” says Rachel Land, yoga instructor and Yoga Medicine therapeutic specialist. But only if two conditions are met: you maintain more of a neutral spine (instead of rounding your back as you lean forward) and you hover the bottom elbow off the bottom knee rather than force it to touch.

As in Triangle, your transverse abdominis and rectus abdominis activate to keep your spine neutral in this pose. The internal and external obliques are at play to help you twist your upper body.

Side Plank (Vasisthasana)

The quintessential core-activating pose, says Land, is Side Plank. “Like Triangle Pose, it engages both abdominis muscles by side bending and balancing. It also engages your inner and outer obliques to help with balance,” says Land.

This article has been updated. Originally published June 2, 2022.