[Exploring Life] The word core means the center of an object. The Earth’s core, for example, is also referred to as the center of the Earth. The core area, or centre, of the body is the site of the internal organs. The core area includes the entire area from the diaphragm down to the base of the pelvis. Core development means the integrated and coordinated development of muscles, internal organs, posture, and breathing. With respect to exercise, the core area of the body is the single most important consideration in any fitness program. In this article I will explore the basic musculature of the core area, developing body awareness of the core, and defining principles for the correct development of the core area.
Core Definition: The Site of the Internal Organs
Peritoneum: The internal organs of the core, or viscera, are contained in a protective bag of fascia known as the peritoneum. Fascia is a sheet or band of fibrous connective tissue that serve the purpose of separating or binding together muscles and organs. Our entire body is permeated by a vast, connected matrix of fascia that surrounds and penetrates our bones, muscles, organs, nerves and blood vessels. The peritoneum is an area of fascia that plays an important role in protecting the internal organs:
The peritoneum, covers almost the entire intestine, and all the other internal organs: it facilitates movement, even if it keeps the organs in their original place; it protects the abdominal cavity from pathogenic agents, thanks to the secretive and absorbent characteristics of its epithelium. It is highly vascularized and it allows amino acids, monosacchardes, glycerin, vitamins, water and mineral salts to enter the mesenteric blood circulation. [1]
The back of the peritoneum is protected and supported by the spine and the pelvis. The front of the peritoneum is protected by two an inner and outer layer of abdominal muscles that form a girdle across the abdomen. One important function of the core musculature is to provide support and protection for the internal organs. (See Gray’s Anatomy: The Abdomen)
Basic Musculature
The core musculature may be divided into two layers, the inner core and the outer core.
The Inner Core: The deepest layer of core stability muscles are the transverse abdominis, the multifidus, the pelvic floor (or perineum), and the psoas muscle. While all muscles interact together and their development must be coordinated and balanced, these muscles provide the deepest level of core stability.
- Transverse Abdominus: The central muscle of the inner core area is the transverse abdominus (TA). It is the deepest layer of abdominal muscle that wraps horizontally around the abdomen. It’s main role is to stabilize the trunk and maintain abdominal pressure. The TA originates in the spinal column of the lumbar region and wraps around the inner abdominal area horizontally. Since it is attached to the spine it is the most important muscle for stabilizing the lower back (lumbar) area. The action of the TA is a squeezing motion. Through the lumbar fascia, the TA connects to the multifidi, which are tiny muscles that run between the lumbar vertebrae. [See Muscles that Act on the Abdomen]
- The Multifidus: The multifidus is a very thin muscle deep in the spinal column. The purpose of it is to stabilize the spine and it works together with the TA and the muscles of the pelvic floor. When healthy, the multifidus will anticipate action and prepare the spine for movement; when unhealthy the multifidus is slow to react leading to pain and potential injury. The main purpose of the multifidi are to stabilize the segments along the entire range of the spine. When the multifidi contract they provide support for the spine and allow us to be in an upright position. The lumbar multifidi are located in the lower back region. Both the multifidus and the transverse abdominis work in unison to provide spinal stability and protection. In other words, the TA and the multifidus are in constant communication about the condition of the spinal column. If the TA is weak then the action of the lumbar multifidi are strained. If the lumbar multifidi are weak the ability to contract the segments of our spine in the lower back are impaired. The TA and lumbar multifidi must work in balance to stabilize the core. (See Gray’s Anatomy: 6. The Fasciæ and Muscles of the Trunk. a. The Deep Muscles of the Back)
- The Pelvic Floor: The pelvic floor is a diamond-shaped area defined by the two sit bones, the tailbone, and the pubic bone. It consists of a band of muscle extends approximately mid-way across the diamond dividing it into two triangles. The pelvic floor is the base of the core and fundamental to posture and core stability and separates the internal organs from the perineum. A weak TA creates a feeling of constantly “bearing down” resulting in a protrusion of the abdomen. This is turn weakens the natural lift and muscular support of the perineum resulting in a degradation of the core area. Both the TA and the muscles of the perineum need to work in balance. (See Gray’s Anatomy: 6e. The Muscles and Fasciæ of the Pelvis)
- The Psoas Muscle: The psoas muscle is the only muscle that links the lower (lumbar) spine to the legs. This muscle is essential for balance, alignment, joint rotation and range of motion. The psoas muscle also influence the circulatory system, functioning of the internal organs, as well as breathing. Though we often think of the core in terms or strength or stability, the core area is also critical to postural integration and alignment. Postural misalignment, regardless of the strength of our muscles, eventually leads to pain. The psoas muscle lies at the intersection between our legs and our upper body. An underdeveloped psoas muscle makes us feel heavy and imbalanced on our feet. When our body is imbalanced our mind naturally follows and this can create a sense of emotional instability within. (See Muscles that act on anterior thigh: Psoas Major Muscle. [2]
The Outer Core: The group of muscles comprising the outer core are not attached to the spinal column, and therefore do not provide the spine with direct support. These muscles include the rectus abdominus, and internal and external obliques.
- Rectus Abdominis: On the surface of the abdomen between the ribs and pubic bone. It’s main role is to move the body between the rib cage and the pelvis.
- External Oblique Muscles: On either side of the rectus abdominus, the external oblique muscles allow the trunk to twist. Contraction of the right external oblique twists the body to the left.
- Internal Oblique Muscles: These flank the rectus abdominus inside the hipbones and function in tandem with the external obliques. Twisting to the left requires the left internal oblique to contract in tandem with the right external oblique. [See Muscles that Act on the Abdomen]
Core Development
Balanced Core Strength: The lower back has a natural curve that is an important aspect of healthy posture. Straightening the lower back, as called for in many exercises, activates the outer abdominal muscles to push the lumbar curve straight. The TA is not involved in this action. Squeezing in from all sides of the lower abdomen while maintaining the natural lumbar curve in the lower back does engage the TA. Learning to feel the difference between these two actions is one way to isolate the action of the TA.
Research suggests that the secret to prevention and elimination of low back pain is sustained contraction of the TA …outer corset emphasis can actually overwhelm the inner corset and make it weaker… If you have an underactive TA, standard abdominal exercises will not engage it and will, in fact, override it. Core strengthening programs are successful only if you can distinguish the subtle sensation of TA activity clearly enough to be sure you are using it. [3]
The sustained contraction of the TA refers to maintaining a sense of gently squeezing inward and upward in the lower abdominal region between the pelvic floor and navel. Learning to maintain an active TA changes the sensations in the body due to the realignment of central support. When our TA is inactive there is often a sense of bearing down as revealed by a protruding stomach and a general slouching over from the neck down to the hips. Properly activating and sustaining the TA reverses these conditions and sensations by creating a natural inward and upward life between the pelvic floor and navel. This opens the abdominal area, provides lower back support, and creates more space for the motion of the diaphragm.
Breathing and the TA: The diaphragm is a muscle that lies between the thorax and the abdomen and plays a key role in breathing. During inhalation the diaphragm contracts increasing space in the chest area: when it relaxes air is exhaled. The diaphragm interacts with the muscles of the abdomen, which function as an antagonist to the motion of the diaphragm. A weak TA causes the body to slouch forward pressing the thorax down on the abdomen. This in turn restricts the normal functioning of the diaphragm and results in abnormal patterns of breathing, which has a range of negative physiological and psychological effects. If the outer core muscles are contracted, breathing becomes difficult since the movement of the lower rib cage is restricted. Contraction of the TA muscle does not interfere with the movement of the lower rib cage during breathing.
Pressure on the Internal Organs: A weak core area directly affects the operation of the internal organs. Closure, or consistent downward pressure on the stomach, inhibits blood circulation as well as the effective exchange of oxygen and carbon dioxide in the bloodstream. This places the internal organs in a constant state of stress and can result in a range of symptoms including digestive problems and incontinence.
Habitualization of Tension in the Body and Mind: An imbalanced core area affects both body and mind. Although we can become tolerant of unhealthy states of stress, the subconscious habitualization of tension in the core area can lead to physical and emotional difficulties. In this sense, the muscles of the abdomen can directly contribute to our states of mind.
Notes
1. Lazzetti and Rigutti. The Atlas of Human Anatomy, 2002.
2. A good overview of the psoas muscle is Psoas: The Forgotten Muscle.
3. Bond, Mary. The New Rules of Posture, 2007.
