Dr. Andy Galpin

Anatomy-wise, there's the three big groups, rectus abdominis, your internal and external obliques are oftentimes smashed together and just called your obliques, and your transverse abdominis, and then you've got those other set of core muscles.

Focusing on the rectus abdominis first, you may be surprised to realize it's not actually one muscle.

In fact, if you've ever seen that person that has their shirt off and they either have 10

And you're like, that person doesn't have a six pack, they have a 10 pack.

Or they actually have a different number.

Like got four on one side and five on another, or they're completely offset.

That's actually because it's not one muscle, it is more like a series of little muscles with a load of connective tissue that helps it transmit force.

So the rectus abdominis actually starts just below your sternum, attaches to the bottom of your rib cage on the front side, and goes all the way down to the front of your hip bone.

And so the main activity of the rectus abdominis is actually to pull your rib cage down.

So when we get into things like a sit-up exercise, sometimes people will actually be sore or have pain in their hip flexors when they do them.

That's generally because the rectus abdominis, again, is supposed to move your rib cage up.

And so if you're not executing that exercise properly and you're getting success with flexion by moving your hips rather than your ribs up,

then the hip flexors themselves and things like the psoas major tend to get sore or fatigued.

It's also in large part why people who get back pain from this type of activity get it.

Oftentimes they're doing the exercise again incorrectly and they're using more of the pelvis for the flexion portion rather than the rectus abdominis itself.

So that's that particular muscle.

Again, that's the one we think about when we think of, I want nice abs.

We're almost always looking at the RA muscle.

That's how we call it.

The obliques themselves are on the side.