Core Muscles in Synchronized Swimming

It’s a part of your body you never even thought about until your coach started demanding that you use it: your core.

But what, exactly, is “the core?” You may be surprised at how many muscles are contained in the imaginary corset that forms the center and stable base of your body. It's important to both strengthen your core with crosstraining and learn to engage the entire area during synchro practice, until it becomes second nature.

Here’s a guide to all those different muscles, separated into five main categories: the abdominal muscles, the lower-back muscles, the pelvic floor, the hips and the glutes.

Abdominal Muscles

External Oblique: The external oblique is the largest of the three flat muscles on the side of the abdominals. It’s not very thick, but spans wide and has a kind of square shape. The external oblique pulls the chest downward, which compresses the abdominals.

Internal Oblique: The internal oblique is located just below the external oblique, on the side of the abdominals. It’s perpendicular to the external oblique and stretches from the lower back to the upper part of the hip bone, with fibers connecting to the tenth and twelfth ribs. The internal oblique contracts when the diaphragm expands during breathing. It also pulls the rib cage and abdominal midline toward the hip and lower back when the side bends.

Transversus Abdominus: Just underneath the internal oblique lies the transversus abdominus muscle. It originates near the inside of the front of the hip bone and runs up to the twelfth rib. It’s the deepest of the major abdominal muscles and acts to compress the ribs, providing core stability. When you flex and flatten your abs, you engage the transversus abdominus more than any other abdominal muscle.

Rectus Abdominus: The rectus abdominus is the muscle more commonly known as (when well defined) a six-pack. It’s actually comprised of ten sections, with five on either side of the abdominals. It functions to flex the lower back, help breathing, and protect the internal organs.

Pyramidalis: Behind the rectus abdominus lays the pyramidalis muscle. This muscle is shaped like a small triangle, but is actually non-existent in 1/5 of the population. It serves to tense the linea alba, part of the connective tissue in the abdominals.

Lower-Back Muscles

Erector Spinae: The erector spinae connects along the spine and is comprised of not one, but many muscles: the illiocostalis, longissimus, and spinalis. They all work together to extend the spine.

Serratus Posterior: The serratus posterior begins at the eleventh vertebra, runs sideways and upwards in a rectangular shape, and eventually connects to the lower parts of the ninth, tenth, eleventh, and twelfth ribs. It acts to pull the lower ribs back and down, which also helps expel air out of the lungs. It is one of the muscles, like the transversus abdominus, that you feel most when flexing the abdominals.

Latissimus Dorsi: Stretching from the top of the back side of the pelvis all the way up to the underarm, the latissimus dorsi is roundly-shaped muscle that becomes thinner as it spans upward. It functions to extend and laterally flex the lower back, as well as rotate the shoulder joint.

Pelvic Floor

Levator Ani: The levator ani is a thin, wide-spanning muscle comprised of three smaller muscles that form the inner side of the pelvis. It acts to support the sides of the pelvic cavity, forming a sort of muscular wall on the inner sides of the pelvis.

Coccygeus: The coccygeus is shaped like a triangle and located behind the levator ani. It contracts inward to pelvic tilt. It also borders the sacrum, one of the fused bones located in the lower back, and is known sometimes known as the “tailbone muscle.”


Iliopsoas: Comprised of the psoas major, psoas minor, and iliacus, the iliopsoas is the strongest of the hip flexor muscles. It starts at the bottom five vertebrae of the spine and stretches into the inner part of the pelvis. It acts to flex the hip, a vital action for any movement—from walking to running to sitting down.

Lateral Rotator: This group of muscles functions to rotate the legs from the hip sockets into a “turned out” position. It is comprised of six different muscles (PGOGOQ): the piriformis, gemellus superior, obturator internus, gemellus inferior, obturator externus, and quadrates femoris.

Hot Tip: Pilates for Synchro

In Pilates sessions, the core muscles are the focus of many of the exercises. It is the cross-training workout of choice among dancers, but is also great for synchro swimmers. The Pilates method teaches body awareness and helps students learn to more effectively control their entire core area.



Gluteus Maximus: The largest of the gluteal muscles, the gluteus maximus is known more casually as the “butt muscle.” It is connected to the iliotibial band and stretches to the lower back. It acts to both turn the legs outward and to stabilize the pelvis.

Gluteus Medius: The gluteus medius is a four-sided muscle, located on the outside of the pelvis. It acts to abduct (pull away from the center of the body) the thigh, as well as support the pelvis when weight is shifted from one leg to the other.

Gluteus Minimus: The smallest of the three gluteal muscles, the gluteus minimus lies directly below the gluteus medius on the outside of the pelvis. It assists in the abduction (moving towards the center of the body) of the thigh and to rotate the legs inward.

Knowing Your Core

It may seem like a lot to think about, but having a general idea of this group of muscles will make it easier to design an effective workout routine. You should feel each muscle working hard during every class and cross training session.

The core is, after all, the center of our body—the foundation that drives all movement. And the stronger your foundation, the better synchronize swimmer you will be.

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