Maybe it was in a yoga class or an advertisement on television promoting the latest workout craze, but it’s a safe bet that most people have at one time or another have heard that there is something called “the core” and that it’s something they need to exercise. But how many of those people actually know what “the core” is and whether or not they need to work on theirs?
Simply put, the core are a group of muscles that exist between the bottom of the rib cage and the upper thighs and are some of the most important muscles in the human body. Seriously. It may seem that having strong and healthy core muscles is only important to people who want to have sexy abs or a trim tummy region, but the reality is that these muscles assist in a variety of ways that contribute to balance, digestion, and protecting the torso from muscle strains and damage.
The core is made up predominately by five separate muscles – the transversus abdominus, the internal and external obliques, the psoas major, and the illiacus. The two other major muscles involved in the movements of the torso – the rectus abdominus and paraspinals – can sometimes be considered as part of the core muscles, but as will be explained, these muscles can often be part of the problem when dealing with issues related to weak core muscles.
The first three muscle groups – the transversus and the obliques – combine to form what can be called the ‘corset’ muscles. Each of these muscles exist separately on the left and right side of the body and form a wrap around the torso which can be visible to the naked eye in people who have both a strong core and low body fat. The transversus abdominus muscles start in the rear of the torso and connect to a large sheet of connective tissue near the spine called the thoracolumbar fascia. These muscles travel laterally around the body and connect in the abdominal region near the center line of the front of the body and are involved in movements such as rotation of the torso. The obliques are made up of two separate muscle pairs, the internal and external obliques, and which connect the ribs to the pelvis in the front of the body. They assist in movements which involve rotations that have a vertical element as well as a horizontal one. Think of bringing an elbow on one side of the body to the knee on the opposite side, or chopping wood, and that’s the type of movement that makes use of the obliques.
The second two muscle groups – the psoas and the illiacus – are mainly used in providing the initial force in flexing the thigh at the hip, or to put it another way, in raising the legs in front of the body. Both of these muscles are ones that most people will never see, but which they use all of the time. The psoas major muscle starts on the front of the lower lumbar vertebrae and travel through the center of the body to connect to the femurs (the bones of the upper leg) just below the groin. The illiacus muscles originate inside the bowl of the hip muscles and connect in a space near the psoas on the femur. These muscles work in tandem to lift the upper leg toward the torso as when raising the leg in front of the body.
The final muscles that were mentioned – the rectus abdominus and the paraspinals – aren’t strictly core muscles, but they are involved very strongly in posture and can have a significant impact on movements involving bending or extending the upper body and hips as well as with posture. The rectus abdominus is commonly referred to as the ‘six-pack’ muscle and is the one that receives the most attention when it comes to what is commonly thought of as a pleasing abdominal aesthetic. This muscle runs down the center of the torso and is primarily used when bending forward through the waist and hips (or a bowing motion). The paraspinals provide much of the opposition to the rectus and are what are known as extenders. These muscles run from the base of the skull on either side of the spine to the top of the sacrum and hips and pull the body backwards. (If the rectus is the bowing muscle, then the paraspinals are what pull the body back upright.)
Structurally, these core muscles provide much of the support that is required to keep the body upright and are in use constantly, even when lying down. Whenever a child is told to stop slouching, what is actually being said is for that child to engage these muscles to keep the torso straight so that the shoulders are above the hips and the spine is in proper alignment. When this posture is not being kept, strain is put on the back, especially the low back, and the organs of digestion and respiration are often being adversely affected.
To look at it another way, the muscles of the core form a column that connects the upper body (for the purposes of this example, the head to the bottom of the rib cage) to the lower body (the top of the pelvis to the feet). When the core is weak, the rectus abdominus and the paraspinals will still allow the person to maintain an upright position, but in effect, the column has been removed and all that is holding these two body parts together is a pair of two by fours, one in the front and one in the back. As can be imagined, this is far less structurally sound than the column would be, with a lot more constant strain being placed on the muscles involved and potential for problems when movements such as twisting are performed or over extended periods of time. An example of this would be lifting something up from the ground. If there is a twisting motion that occurs when lifting a heavy object, in a person with a healthy core, some of the impact of that force would be transferred into one of the muscles on the side of the abdomen, but if those muscles are absent, strain to the back is often the result.
The muscles of the core also aid with internal processes, specifically digestion. When food moves through the intestines, it does so mainly through the contractions of the smooth muscles that line the small intestine. This series of contractions is called peristalsis and, combined with the force of the food consumed after what is being focused on, gradually moves the digesting mass from the small intestine to the large intestine and finally out of the body. When the core muscles are strong and engaging on a regular basis, they apply and release pressure on the intestines which aids in the movement of these materials through the digestive system. When this help is absent, however, the organs of digestion must then work harder and as a result, food moves more slowly, which creates some problems that will be detailed below. When those same core muscles are also weak, then not just the digestion is affected, as the respiration also suffers.
What often happens is that the muscles of the rectus abdominus become much stronger than those of the paraspinals, which pulls the front of the pelvis upward. This then forces the paraspinals to exert more force on the back of the pelvis to maintain the lumbar curve. As a result, the psoas muscle then tightens in response to reestablish the lumbar curve. The psoas muscles travels past the intestines as it goes from the spine to the legs, and when it becomes tight, it can actually obstruct the large intestine, affecting the body’s ability to eliminate waste and causing pressure to build up. This pressure, combined with the added mass of the waste that can no longer pass through the large intestine, begins to compress the small intestine, causing it to become more bloated and filled with pressure. That will have a negative impact on its ability to break down foods and will result in more gas and bloating. As a result of the organs of digestion being taking up more space, the diaphragm (a muscle which pushes the intestines down toward the pelvis in order to draw air in to the lungs) is unable to move as far downward, meaning less air is drawn in when a breath is taken. Another affect of the movement of the diaphragm is to add extra mechanical effort to digesting foodstuffs as they move through the digestive organs. So when it doesn’t move as freely, then food moving through the organs of digestion doesn’t travel as quickly, giving it even more time to ferment, which adds to the amount of gas and bloating experienced in the abdomen. This cycle can continue to the point where the extra gas and undigested food can actually increase the protrusion of the abdomen, giving it a distended appearance as well as increasing its forward and downward drag on the torso, which puts further strain on the lumbar.
In women, this added pressure can also have a negative effect on the menstrual process, increasing the incidence of cramping and bloating during their cycle. Without strong core muscles to aid the uterus in the contractions that occur during menses, and with the added pressure from both the tight psoas and the added mass in the intestines, the uterus will often have to strain harder and cramping can become a much more common occurrence. This also means that not all of the tissue is expelled which then creates a cycle of building cramps with each subsequent cycle.
When these muscles are weak or have developed out of alignment, balance can become negatively affected, as well. In younger people, this loss of balance is relatively unnoticed, but as an individual becomes older, it becomes a serious health concern. Falling is often seen as a predicator of major health issues in the senior population and a fall that results in a broken hip can often lead a person to develop serious illnesses over a relatively short period of time. But it’s not only seniors who need to be concerned with a weak core or the problems that can result from the muscles being out of balance or too weak. Even in younger people, a weak core can increase the incidence of falls and serious injury as the body is less able to absorb the impact in a way that minimizes damage to the body. Over an extended period of time, a weak core can also create permanent damage to the spine and joints by creating a situation of building pressure that manifests in a need for surgical intervention.
As mentioned above, a tight psoas will pull the lumbar vertebrae forward, a situation which increases the chance of a forward subluxation of the vertebral disc (where the disc slips forward so that it is out of alignment with the discs above and below it). This can then put a significant pressure on the spinal cord and nerves which connect to the lower body, such as the sciatic nerve. As a result of this pressure, pain and numbness can result. When left untreated and uncorrected, this pressure will often require surgical intervention that may result in the fusion of the vertebrae or removing sections of bone in order to ease the pressure.
In an effort to protect the spine, the body will often make adjustments to the alignment of the knees and hips to alleviate the pressure, but these adjustments over the long term carry the possibility of increasing the wear and tear on these joints. As a result of this wear and tear, the hips and knees will develop problems of their own and once they are no longer able to tolerate the alignment changes, they may also develop chronic pain to the point where those joints may lose the ability to properly function.
Much of the modern study of the core comes from disciplines such as yoga, the martial arts, and Pilates. Pilates is a type of exercise that was originally developed by Joseph Pilates in part as a way for injured dancers to stay in shape and for healthy dancers to avoid injuries. The focus was on building a frame that was simultaneously strong and yet still lean and flexible, where power and strength were built without increasing the mass. This is incredibly important for dancers as too much mass comes at the cost of speed and ease of movement, things which are obviously important when there is a need to move quickly and in a variety of directions, including leaping and twisting.
One of the nicknames for the core is ‘the powerhouse’ because a healthy core will allow a person to utilize more strength than they could with their extremities alone. Much of this comes from the benefits it provides with regards to proper alignment and balance. When the core is strong, less effort is required by the legs and arms in order to protect the back both when moving and lifting both objects and the body itself, easing strain on the joints and connective tissues, which gives a greater sense of security and coordination as well as allowing a maximum of force with a minimum of effort. In the absence of a weak core, these benefits are considerably minimized, but this may not be readily apparent due to the body’s amazing ability to compensate for weakness.
As mentioned above, strong paraspinal muscles combined with a strong rectus abdominus may contribute to the problems of a weak core. This occurs because while these muscles may offer the illusion that the torso is unaffected, over time they will be unable to protect the body from certain movements while in some cases the forces they exert on the skeleton and joints may contribute to the very problems they were helping to initially hide. Exacerbating this situation is the fact that many individuals will focus on strengthening these muscles to the exclusion of the other muscles that make up the core, often under the mistaken belief that their efforts are in fact helping to relieve the very problems they are trying to avoid.
Sit-ups are one of the first exercises a child learns and they focus almost exclusively on the rectus abdominus muscle. The core muscles are engaged, true, but only for the first few inches of movement. To look at it another way, humans spend much more time with the their torsos flexed fifteen degrees forward or backward than they do with the more extreme flexion seen in a sit-up, where the torso may be flexed up to ninety degrees. A tight or overdeveloped rectus abdominus also makes bending backwards more difficult as well as flattening the lumbar curve. This is important because on the reasons for the lumbar curve is to help absorbs shocks that may affect the spine from activities such as jumping, running, or walking.
Speaking of walking, walking is one of the best exercises to maintain a healthy core. When walking properly, the torso engages in small rotations that engage the transversus and oblique muscles, which tones and strengthens them. One way to diagnosis a person with a weak core is to watch them walk. If they move in a very straight manner with little rotation of the core and hips, it is often due to weakness of those core muscles. Dancing is another activity that can both benefit and benefit from stronger core muscles. Belly dancing specifically uses the core muscles in order to accomplish its signature movements of the hips and torso.
Other exercises can also help develop the muscles of the core and in almost every case, small movements accomplish more than large ones. Leg lifts where the legs are brought just an inch or two off the ground and crunches that involve just lifting the shoulders from the ground are just two examples of these types of exercise. Pilates, as mentioned above, focuses on the core primarily and the explosion of related videos and classes has made it easier than ever to engage in. Caution should be used, however, as improperly performed movements can jeopardize the core, so professional instruction should be obtained before trying any tapes or home programs. Yoga can also provide benefits to the core, but the same cautions should be exercised.
This article was intended more as an introduction to the core and its relationship to the body, and should not be seen as a comprehensive guide to this important yet often ignored aspect of the body. Please feel free to engage in further research into both how these muscles work and how they effect the body, and while there are other articles on this blog that relate to both it and exercises that can benefit it, please don’t hesitate to seek further information either online or from a trained health or fitness professional. Hopefully, this served to illuminate a much talked about but little understood aspect of the body. As always, be safe and be healthy.