If the spine were subjected to an external force which is strong enough to overcome the resistance of the body's muscles and ligaments, a vertebrae will misalign or subluxate. This is a very simple principle. If you tap an nail lightly against a wooden board, nothing happens, because the force of the hammer (the outside force) is not strong enough to overcome the internal resistance of the wood. Strike the nail forcefully, and the nail will move.

There are various kinds of external, invasive forces that affect the spine. They can be put into three classifications: physical, chemical, and mental / emotional.

Physical forces
Physical forces are probably the most well-known and most easily understood. It is not difficult to see how a physical trauma could cause a vertebra to subluxate. Falling down a flight of stairs or being run over by a truck are physical traumas which are sure to cause vertebrae to misalign from their normal position and interfere with normal nerve transmission.

The automobile accident that causes a whiplash is another such physical trauma. Almost everyone has felt the trauma of walking down two steps when there were actually three, or down three steps when there were only two. All of these traumas are physical forces that could be sufficient to subluxate the spine.

Another physical trauma which is not easily understood is subliminal, constant trauma. The mail carrier who carries the weight of the mail bag on only one shoulder is an example. The data processor who sits at a keyboard with his or her head turned at an angle for hours each day is another. Sitting, standing, learning to walk (a child will fall on its rear an average of 3,000 by the time they are 3 years old), the birth process, and sleeping incorrectly over periods of time are physical traumas which could also cause subluxations.

Chemical forces
It is an accepted fact that a chemical can affect the tone of a muscle. Remember that the alignment of the spinal segment is dependent upon muscle tone. Lack of calcium, for example, can cause muscle spasm. A build-up of lactic acid (a by-product of muscle exertion) can cause cramps which athletes sometimes experience. Drugs can also affect muscle tone. The body has a delicately balanced chemistry. Anything that upsets this chemistry such as smoking, alcohol, caffeine, processed foods, pollution, food hypersensitivities/allergies, etc. can irritate the nervous system causing abnormal functioning of the muscle fibers, upsetting muscle tone, and cause a subluxation.

The causes of a chemical imbalance in the body sufficient to cause subluxation are numerous. If we were aware of all the chemicals that we place into our bodies, in the water we drink and the food we eat, it would frighten us. The body has the ability to remove many of these poisons, but if sufficient poisons are taken in, even the body's filtering mechanism can be overcome.

Emotional/Mental forces
By far, the most common causes of subluxations are emotional forces. Our society's lifestyle has caused the emotional factor to be one of the most important factors causing subluxations today. We live in a fast-paced, tension filled society. If you have ever been in a tense or emotional situation (worry, fear, anger, etc.), you can remember how the muscles in the back of your neck and across your shoulders tightened. This muscle tension can cause a vertebra to subluxate.

Combination of all three
Although each of these three forces can cause a subluxation by themselves, most subluxations are caused by some combination of the three. A slight physical trauma, which ordinarily would not cause a subluxation, does so because of muscle tension due to emotional factors. Normal stress and strain of daily life may prompt muscles that are full of toxins and chemicals to allow subluxations to occur. With all the stresses, physical traumas, and emotional tension as well as the poisons that our bodies are subjected to each day, it is not difficult to see how the spine can become subluxated.