Bodybuilding Anatomy: Muscles of the Core

What are Core Muscles?

What many people don’t know is that core muscles are actually the “core” or central part for all the strength needed to carry out different physical activities. This means if an individual’s core muscles are physically fit, they will maintain equilibrium of the body, and will stabilize the system every time the person is working out or moving around.

The core is not just the four major muscles making up the abdominal group. When many people think of core training, the first thing that often comes to mind is sculpting the “six pack”, so they focus primarily on training the rectus abdominis (the abs you see when you look in the mirror).

In reality, your core is composed of many muscles in the abdomen, hips, back, butt, and legs, and it’s necessary to work all of these muscle groups to build a strong core. The core is at the center of the body’s power, coordination, and stability. Think of your core muscles as the sturdy central link in a chain connecting your upper and lower body. These areas of the body are the ones that usually frame the posture of a person and they are vital for body mechanics, strength, endurance, balance, and all activities encountered during daily living. Therefore, a good posture reflects the good condition of these muscle areas.

The Core Muscles

Different experts include different muscles in this list, but in general the muscles of the core run the length of the trunk and torso. The following list includes the most commonly identified core muscles as well as the lesser known groups.

The following muscles are considered core muscles:

The abdominal muscle group:

Rectus abdominis (1)
External oblique (2)
Internal oblique (3)
Transverse abdominis (4)

The stabilizer muscles of the spine, which include the back (erector spinae) group of muscles:

Iliocostalis (5)
Longissimus (5)
Spinalis (5)

Muscles of the hip joint (muscles which attach to or cover the hip joint and generate the hip’s movement):

Gluteals: gluteus maximus (8), gluteus minimus and gluteus medius (9)
Hip flexors – psoas major and iliacus (6) and hip adductors (7)
Piriformis (10)
Hamstrings (11)

Muscles of the Core – Function and Location

RECTUS ABDOMINIS (also known as the six-pack): It’s the large, long and flat muscle that defines most of the front of your midsection from the lower chest to the pubic bone. Despite its nickname, this muscle actually consists of eight segments that are separated by a dense connective tissue called fascia. The rectus abdominis flexes (bends) your torso by pulling your rib cage toward your hips, or vice versa. That’s why you can work this muscle by doing situps and crunches.

EXTERNAL OBLIQUE: The external obliques are easily identified along both sides of the abdomen (outer visible layer that passes obliquely downward from the rib cage to the pelvic bone) if you keep your hip stationary. They lie adjacent to the rectus abdominis and directly above the internal obliques. Your right and left external oblique muscles help you flex your torso towards your hips, also flex your torso to the sides and rotate your torso to the other side.

INTERNAL OBLIQUE: The internal obliques are located underneath the external obliques and above the transverse abdominis. In other words, this is the middle layer that passes obliquely upward from the pelvic bone to the ribs. They work with the external obliques to flex and rotate the torso.

Muscles of the Core

TRANSVERSE ABDOMINIS: The transverse abdominis sits immediately beneath the internal oblique muscle, and is the deepest of all your abdominal muscles (innermost layer of the abdominal muscles). It’s a thin strip that runs horizontally across your abdomen. The internal obliques and transverse abdominus cannot be seen because they lie beneath the rectus abdominis and external obliques. This muscle is continuously working when you’re sitting and standing and helps support your lower back and keep good posture.

ERECTOR SPINAE: This large, powerful muscle group runs along the side of your lower spine. This is a group of three muscles: the iliocostalis, longissimus, and spinalis. They run parallel to each other down the length of the vertebrae, from the sacrum to the neck. Erector spinae erects your spine, straightening your torso out of a bent position. The pair also helps your obliques as you twist at the waist.

HIP FLEXORS: The muscles opposite your gluteus maximus, located at the front of your hips. Your hip flexor muscles help you lift your leg up high so you can march in a parade or step up onto a ladder. In other words, the hip flexors are responsible for bringing the legs into flexion and in toward the trunk. They include the psoas major, iliacus, rectus femoris, pectineus, and sartorius.

HIP ADDUCTORS: The muscles that span the inside of your upper leg or inner thighs. This group of muscles includes the adductor brevis, adductor longus, and adductor magnus. They are used in the adduction of the hips (e.g., crossing your legs) and to balance the pelvis while standing and walking.

GLUTEUS MAXIMUS: This big muscle that gives shape to your butt is located in the buttocks and is the strongest muscle in the human body, shaped like a construction helmet and covering the rear of your joint. The gluteus maximus straightens your legs from your hips when you stand up and propels you forward when you walk or run. It is responsible for movement of the thigh and hip, and many everyday movements, including standing up, maintaining erect posture, and climbing stairs.

GLUTEUS MEDIUS AND GLUTEUS MINIMUS: These muscles are located along the side of the hip and buttocks. They facilitate hip abduction and help stabilize the pelvis.

PIRIFORMIS: This muscle is located parallel to the gluteus medius and under the gluteus maximus. The function of the piriformis is to laterally rotate the hip.

HAMSTRINGS: The hamstrings, located behind the thigh, are a group of three muscles that all originate from the ischium bone of the pelvis: semitendinosus, semimembranosus, and biceps femoris. The hamstrings are responsible for bending and extending at the knee. This muscle group plays an important part in activities such as running, jumping, walking, and more.

Benefits of Good Core Strength

Your core muscles are probably the most important group of muscles in your body. The building of core muscles is a must-do for all bodybuilders and weight lifters for many reasons: