Modeling Good Posture
Changes in bone density and bone strength are real problems for us as we age. The medical term for this is osteoporosis. Ten million adults in the United States have osteoporosis. Another 18 million are at risk for osteoporosis and bone fracture.

In this study, chiropractors and engineers worked together to build a computerized model of osteoporosis. They used advanced technology with math equations to predict who's at risk for vertebral (spine) fracture. The model is based on X-ray studies of real spines. The equations included values for bone stiffness and elasticity.

This model shows the chances of bone fracture at each age under different loads. A normal, healthy spine can withstand high loads. As we age, gravity, body weight, and repeated loading cause forces too great for the bone structure. This is because the bone has become thin, weak, and less stiff.

The authors report that forces on the spine are greatest in the middle of the upper back. By age 90, the vertebrae can only support one-fourth the load that can be supported at age 30. Gravity and weakness cause changes in the adult's posture. We become more stooped over. This puts pressure on the front part of the vertebral bones. The bone may then fracture or collapse.

When this happens, the bone takes on a wedge shape. The result is a decrease in bone height, resulting in a loss of total body height. The spine curves forward, the head moves forward, and the person becomes more stooped. This posture puts an increased load on the back muscles.

The authors conclude that this model points us in the right direction for treatment. Exercises, bracing, or other rehab methods can be used to reduce stress on the spine. These measures help reduce the risk of osteoporotic fractures.
References
Tony S. Keller, PhD, et al. Prediction of Osteoporotic Spinal Deformity. In Spine. March 1, 2003. Vol. 28. No. 5. Pp. 455-462.