Part I: The Core – Anatomy

Note: This will be a multi-part series on the core and the proper ways to train and engage the core throughout exercise.

The Core. You’ve probably heard this term thrown around the fitness world in the recent years. But, what does the term really mean?

The core can be described as a muscular box with the abdominals in the front, the paraspinals and gluteals in the back, the diaphragm as the roof, and the pelvic floor and hip girdle musculature as the floor.

The core is often referred to as the body’s “powerhouse” because its the central region providing a girdle of strength and connecting the abdomen with the lower back and hips.  The abdominal muscles in conjunction with the spinal muscles, create a stable base for generating strength and providing support for all movement.

The core plays a vital role in everyday biological functions, including creating internal pressure within the abdominal cavity, holding the internal organs in place, and helping with the expulsion of air from the lungs and of bodily waste. The core musculature provides an axis of power for the kinetic chain.

The kinetic chain is a movement system consisting of myofascial (muscular), articular (joints), and neural (motor) components. Each of these individual elements are dependent on each other for optimal performance during movement. In layman’s term, every part of the body is connected and work together to produce movements.



Let’s break the core down into its core anatomy (no pun intended 🙂 ):

Paraspinals – There are two major groups of lumbar extensors that make up the paraspinals: the erector spinae and the so-called local muscles (multifidi, rotatores, and intertransveri). The erector spinae is a group of three long tendinous muscles that run the length of the spine. The muscles provide support for spinal flexion (bend forward) and extension (bend backwards) and also aid in stabilizing the spine against sideways movement. The multifidus is a deep series of muscles attached to the spine that work to keep the spine straight and to help stabilize it and to maintain good posture. Atrophy (muscular wasting) of the multifidi has been found in people with lower back pain.

Quadratus Lumborum – The quadratus lumborum is a large, thin, and like the name implies, quadrangular-shaped, muscle that directly inserts into the lumbar spine. The quadratus lumborum works to stabilize the spine against lateral movement, lifting heavy objects, and carrying items in one hand, such as a suitcase or groceries.

Abdominals – The abdomen muscles are a group of four different muscles: the rectus abdominis, transversus abdominis, and the external and internal obliques. The rectus abdominis is commonly known as the “six-pack” muscle. It is mainly involved in flexion. The transversus abdominis is a deep muscle that runs around the abdomen like a girdle holding the core together. The transversus abdominis works to maintain good posture, to maintain internal abdominal pressure, and to support the internal organs. The transversus abdominis is generally very weak in people with lower back pain. In healthy people, the transversus abdominis has been shown to activate before limb movement to theoretically stabilize the lumbar spine. The internal obliques are deep muscles that help the body to rotate and flex to the side. They also aid in maintaining good posture and internal abdominal pressure. The external obliques are superficial muscles located above the internal obliques. They are important for rotational core movements and side flexion.

Hip Girdle Musculature –  The hip musculature plays a huge role within the kinetic chain, especially for all ambulatory activities, in stabilization of the trunk and pelvis, and in transferring force from the legs to the pelvis and spine. The hip musculature includes the psoas muscle group and gluteus muscle group. The psoas (hip flexors) control flexion movements of the hip, such as walking, running, and going up and down stairs. The gluteus minimus is the smallest of the glutes and lies beneath the gluteus medius. It works to lift the leg outward (abduction) and internal hip rotation. The gluteus medius lies between the minimus and maximus. It assists with abduction and rotation (internal and external) and provided stability to the pelvic region. The gluteus maximus is the largest and most superficial muscle of the hips. It works to abduct and extend the hips, while also stabilizing the pelvic region. Poor endurance and delayed firing of the gluteus maximus and medius muscles have been linked to people with lower back or lower-extremity instability. Tight psoas can cause lower back pain by increasing compressive loads to the lumbar disks of the spine.

Diaphragm and Pelvic Floor – The diaphragm serves as the roof of the core. The diaphragm provides some stability to the lumbar spine via contraction during breathing and creating intra-abdominal pressure. A few recent studies have indicated that people with sacroiliac (pelvis) pain have impaired recruitment of the diaphragm and pelvic floor muscles. The pelvic floor musculature is coactivated with transversus abdominis contraction.

Stay tuned for parts II and III where we will discuss mobility, stability, and strength of the core musculature and ways to properly engage and train your core to become a stronger and more efficient athlete!


1. Jones G. Core Strength Training. New York, NY: DK Publishing. 2013.

2. Akuthota V, Ferreiro A, Moore T, Fredericson M. Core Stability Exercise Priniciples. American College of Sports Medicine. 2008; 7(1): 39-44.

3. Akuthota V, Nadler SF. Core Strengthening. Arch Phys Med Rehabil. 2004; 85(1): S86-92.

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2 thoughts on “Part I: The Core – Anatomy

  1. Pingback: Part III: The Core – A Case for a Functional Movement Screen | The Rhyme and Reason

  2. Pingback: What is core training? - JessBFit Personal Training & Yoga

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