Spinal tap: understanding the mechanics of the spine is a smart way to avoid injury

American Fitness, Nov-Dec, 1994 by Cathy Berenberg

Even smart people do stupid things when it comes to lifting weights - all caution is thrown to the wind. What is needed are gym rules for lifting weights so smart people won't hurt themselves. Lifting weights incorrectly can have serious consequences.

The problem is most novice lifters don't understand all movement in the body is integrally related to the mechanics of the spine and pelvis. Here are a few things you should know about the spine to make smart choices about your lifting technique.

The spinal column is made up of the sacrum, tail bone and 24 vertebrae held together by muscles and ligaments. Some of these connective tissues span the entire length of the column, while others hold the vertebral bones together at their joints (facet joints). Between each vertebrae is an invertebral disc.

Flexibility of the spine is determined by movement at the facet joints. Three kinds of intervertebral movement are possible - bending front to back, bending side to side and twisting. These are the same movements possible for the trunk. The spine's flexibility determines the range of motion for trunk movements.

The spinal column must also be strong to protect the delicate nerve roots and spinal cord, which runs down the neural canal. The spinal cord is protected from impact by the spinous process and the ligaments of the spine, but can be damaged by serious back trauma which results in a vertebrae fracture. In fact, if a fractured bone compresses the spinal cord, paralysis can result. Anyone who has ever experienced a bulging or herniated disc can appreciate how important it is to protect the spinal cord and its nerves.

The spinal column is designed so well, it is an engineering feat of strength and flexibility. Its curves can act like arches to displace weight and stress. In addition, the vertebrae that support the most weight are larger. Logically, the largest part of the spine is the sacrum where the entire weight of the upper body is borne.

The soft tissues of the spinal column are another integral part of the structure. The intervertebral discs have elastic properties which act like cushions to absorb stress and protect the spine. The intervertebral muscles and ligaments act as cables bracing the vertebrae together to keep the spinal curves. The spine is also braced by the larger muscles of the trunk, including the abdominals, back extensors, quadratus lumborum and the psoas.

The spine can either be in a loaded (weight supporting) or unloaded state. Carrying babies, books, groceries or any other source of weight will load the spine. The spine is unloaded when no extra weight is being carried.

The spinal column accommodates a heavy load by redirecting the compressive weight in much the same way as a bridge. A bridge is designed to send the weight of traffic in its span down the support columns and into the ground. Likewise, the spine transfers the load away from its span to the legs and into the ground. The curves of the spine and the increasing size of the vertebrae are important in the transfer of this weight.

Unlike a bridge, the spine also permits body movement while it is loaded - even with stressful movements, like carrying furniture up a flight of stairs. In this loaded state, the intervertebral discs are compressed to some extent by the weight of the load. The discs have elastic properties and will resist this compression. They work with the spinal muscles and ligaments to reduce bone-to-bone contact between the vertebrae. If the bones ground against one another at the facet joints, arthritic changes would develop over time. This is especially true of the lumbar vertebrae, as the lumbosacral joint is the most frequent site of spinal pathologies. The work of the discs and the spinal muscles and ligaments is taxed even more when bending or twisting movements are involved.

For example, suppose you pick up a heavy box sitting on a shelf at about eye level. But, the box is a little too heavy. It should be no surprise the next day your back aches. The discs and connective tissues are overloaded, and the vertebrae have to rotate on one another to twist the trunk. The spinal muscles and ligaments work to hold the vertebrae together and maintain the spinal curves. These connective tissues also help the intervertebral discs keep the facet joints from grinding against each other. If the weight is not close to the body, the stress is greater arid the muscles of the back contract to brace the spine. Even so, an injury can occur. The point to be made - don't overload the spine.

When the spine is loaded, avoid twisting movements, bending to the front or back or leaning to the side. To pick up a heavy weight safely, bend the knees, sit back as if you are going to sit in a chair and lower the buttocks until you can reach the weight. Lift with the legs and keep the weight dose to the body. Follow these gym rules for smart lifting.

* Always build from a solid foundation. The initial focus of a training program involves strengthening the abdominals and muscles of the back and hip.