Core Relations

Most people can tell you that the abdominal muscles support the back. But if you really press them for specifics, they may tell you that they are part of the "core" and, as part of that "core," they support the back.

A lot of attention is devoted to the transverse abdominus and multifidi, but dysfunction in these muscles may be more like a "canary in the mine shaft" than the actual problem. The transverse abdominus and multifidi do not have super powers. They are relatively small muscles that provide some support and probably some positional feedback to the nervous system, but they are simply too small to do much of the work needed to support the trunk.

Using the abdominal muscles to increase abdominal and intrathoracic pressure may have long-term ill effects. The abdominal cavity has several weak areas that include inguinal canals, openings for the vena cava, aorta and esophagus, the pelvic floor and the linea alba. Chronic pressurization of the abdominal cavity may cause eventual failure in one or more of these areas.

Abdominal muscles are often strengthened with crunches, curls, sit-ups and ab machines. These forms of exercise do "strengthen" the abdominal muscles, but they also over-recruit accessory musculature such as the anterior intercostals, pectorals and scalenes. Tightness in these muscles is often implicated in patients who have poor posture, neck and shoulder problems. A strengthening exercise such as a sit-up may also train the trunk to be good at doing a sit-up, but the action of doing a sit-up is not used during upright posture. A good strengthening exercise should incorporate elements used in upright posture.

Cylinders and Guy-Wires

When we are upright, the muscles between the ribcage and pelvis need to perform two functions simultaneously. First, when contracted, the muscles in this area form a cylinder. A cylinder or upright tube is able to resist a compressive load. Imagine taking a cardboard tube from a used roll of toilet paper. When you stand it upright on a table, you could place several books on top of the roll and the "cylinder" could easily support the load. Our core should support our upper body on the pelvis the same way. This could be referred to as the "cylinder method" of support.

Secondly, the muscles between the ribcage and pelvis may also function as a guy-wire system. Radio antennas use a system of cables to hold them up. As we move, the muscles of the core may also function like these guy-wires. When we are upright, both methods of support, the cylinder and guy-wires, must function simultaneously at all times. Failure in one part of the cylinder/guy-wire system will overload another part. What we generally see in our clients is failure of the abdominals and overloading of the back.

Postural Influences

Both cylinder and guy-wire systems work best when the skeletal system is "plumb." Plumb is a construction term describing a wall that is absolutely vertical. If the walls of a building are not plumb, then the building will eventually collapse.

Our vertical spines are very much like an antenna mast. When we stand up, our sending and receiving equipment (eyes, ears, nose, mouth) is placed relatively high in the air. If the antenna mast is not plumb, leaning in one direction or another, then the guy-wire system is no longer balanced. If posture is poor, then control of our guy-wire system is no longer balanced. If a cylinder is bent, it will no longer support its load. Poor posture compromises the core's ability to support the upper torso. For optimal function of the core, we need reasonably good posture. A prerequisite for good posture is the ability of each vertebral segment to achieve a neutral position.

How To Start

For the vertebral segments to get to a neutral position, there must be reasonably good flexibility in the scalenes, pectorals, anterior intercostals, hip flexors and the low-back and neck extensors, and each segment of the spine must have the mechanical ability to get to neutral. For the body to effectively use the core muscles, some work on posture is often necessary. To specifically work on the guy-wire/cylinder section, we will generally start with a coordination exercise to re-train these muscles in their specific function.

The main function of the abdominal muscle is flexion of the spine. This can be done from the top down as with a sit-up or from the bottom up as with a posterior pelvic tilt. We use a posterior pelvic tilt. The main function of the back extensors is to extend the spine. Most patients can do an anterior pelvic tilt that isolates only the back ­extensors, but when they attempt a posterior pelvic tilt, they won't use the abdominal muscles. Instead, they will use the hip flexors, quadriceps and/or the upper-chest musculature. The abdominal muscles will generally be dormant. This indicates a gross imbalance in the ability of the patient to recruit the core muscles. If a patient cannot selectively recruit a muscle group, he is probably not using it during upright activity.

To assess and teach the patient to re-train these muscles, we use a modified pelvic-clock exercise, where 6 o'clock is an anterior pelvic tilt and 12 o'clock is a posterior pelvic tilt. The patient will lie on his back with the hips and knees at a 90/90 position, supported on a chair or ottoman. We do not recommend using an exercise ball.

Have the patient execute a very gentle anterior or 6-o'clock pelvic tilt and hold this position for five seconds. The low-back extensors should be the only muscles working. The next step is the transition to 12-o'clock, or posterior pelvic tilt. The patient must do three tasks simultaneously. We tell the patient to keep the thighs and chest relaxed, start relaxing the back muscles, and to think about pulling the belly button toward the chin to cause a posterior pelvic tilt.

Lately, we have been instructing patients to grab their upper thigh for inhibition of the quadriceps and hip flexors and to spread the fingertips of their other hand across the abdominal muscles and literally pull the belly button toward their chin. This usually facilitates recruitment of these muscles. Once they can execute a 12 o'clock tilt using the abdominal muscles only, we have them hold this position for five seconds, then relax. They are then to repeat the entire sequence.

Next: Strengthening

Again, crunch and sit-up exercises pull the upper body into a flexed position. This may worsen posture and is not a functional movement used during upright posture. We will generally use modified leg lifts for abdominal strengthening. The most basic leg lift we use is called "supine heel touchdowns." The patient lies on his back with his fingers placed under the small of the back (not under the pelvis). We ask the patient to do a very strong 12 o'clock (posterior pelvic tilt) to mash the small of the back against the fingers. Now, the knees are brought toward the chest, one at a time, so that both hips are flexed at 120 to 130 degrees.

In the beginning, the patient is asked to keep the knees fully flexed throughout the exercise and to tuck the chin without lifting the head. Then, without straightening the knee, the patient lets one hip extend so that the heel moves toward the floor while keeping the back pressed tightly against the fingers. Let the heel lightly touch the floor, then slowly return the leg to the flexed position and repeat on the other side. The patient must keep the back firmly pressed against the fingers that are under the back throughout the entire exercise.

Patients with very poor abdominal control may only move their leg one-quarter to one-half distance toward the floor, again with the emphasis on keeping the small of the back pressed firmly against the floor. If done correctly, the patient should feel fatigue in the abdominal muscles. A more advanced version of this exercise would be accomplished by letting patients straighten the knee as the hip is extended, but they must be able to keep the back firmly against the floor.

A few clients find the above-discussed exercises too easy. So we will place them on a weight bench with a bath towel folded in several layers so that it is a 12-inch x 12-inch square placed under the back approximately one inch above the pelvis. The knees are bent with the feet resting on the bench and they will hold onto the bench above their head, keeping the arms close to the side of the head. For a warmup exercise, the patient is instructed to bring the knees tightly toward the chest slowly, causing the pelvis to lift off of the bench. The leg and pelvis are then lowered back down to the bench, slowly.

We can use some version of these exercises with almost any patient at any level of pain or debilitation. We often find relatively fit clients struggling with the pelvic clock exercise. These exercises will re-train and strengthen the abdominal muscles without the negative side effect of increasing thoracic flexion. Your patients will like these exercises because they can do them without hurting their back or neck.

Brian P. Lambert is owner of Brian P. Lambert Physical Therapy in Charlottesville, VA.