Anatomy of the Core
Learn about the muscles that stabilize your core and, in turn, your running.
By John Hanc
Image by Supercorn
Published 01/10/2008 Last Updated 02/19/2010

Your core--the roughly 30 muscles that connect your legs to your hips, spine, and rib cage--have a tough job. Namely, to work synergistically to stabilize your torso. This is particularly demanding when you run, since 60 percent of your body shifts in about .02 seconds, says Dennis Kline, the strength coach who designed Team Running USA's core program. Here are the primary stabilizers and how they function when you run.

Obliques: These muscles rotate your torso and work with the transversus abdominis to support your center during movement.

Rectus Abdominis: This muscle is the fitness aesthetic: The contours of the contracted rectus abdominis form the almighty "six-pack." While it helps stabilize your core, its main function is to flex or curl the trunk.

Transversus Abdominis: This deepest of the abdominal muscles wraps laterally around your center, acting like an internal weight belt.

Psoas Major/Iliacus: Better known as the hip flexors, these muscles lift the thigh toward the abdomen and limit excess motion of the hip joint.

Erector Spinae: This collection of three muscles (not shown) straightens the back and, along with the multifidus, a short muscle, supports the spine.