All About Your Back

Click Here for "The Low-down on Gravity" - Information about how your back is affected by gravity.

Today back pain is one of the most common of all physical complaints in the world. About 70 to 90% of men and women in the U.S. have had or will have a least one bout of incapacitating low back pain. Back pain contributes to lost work time and may cost as much as $100 billion annually (if lost productivity is included¹).

Doctors generally agree that most back problems are caused by stress or by weak muscles. We need strong back , stomach, and hip muscles to resist gravity and to hold us up. As societies around the world become more mechanized and computerized, they have also become less exercised. We lock ourselves behind desks and in front of computers. When we sit, our back muscles hold us erect, but our stomach and hip muscles are inactive. When they are not exercised, stomach and hip muscles become weaker, putting a painful strain on the back muscles. Sitting places higher loads inside the lumbar disc than standing (between 150% to 250% depending on posture).

The condition of your back is very important to your health. A better back can lead to a better body.

Anatomy of the Back

Briefly explained, your spine is made up of the following components:

1) Vertebrae - the bones that make up your spine
2) Nerves - your entire nerve system runs through your spine
3) Discs - spongy material that separates your vertebrae, allowing the nerves to run between each bone segment. Discs act like shock absorbers and allow the spine to flex.

Each vertebrae is held in its proper place by three different kinds of soft tissue-discs, ligaments, and muscles. Almost all back problems are related to the dysfunction of one of these three. To understand the sources of your particular back problem and/or how to prevent back pain, it helps to understand the anatomy of your spine.

The natural curves of the spine are vitally important for giving your back strength and resilience. There are 24 vertebrae in your spinal column. The lumbar vertebrae are approximately two inches in diameter reflecting their weight-bearing role. The cervical vertebrae are smaller, since they must support only the head. Facet joints are located in pairs on the back of the spine, where one vertebra slightly overlaps the next. The facet joints guide and restrict movement of the spine. To the rear of each vertebra is a hole and when the vertebrae are stacked up, these holes form a continuous channel which holds the spinal cord.

The spinal cord provides a vital link between the brain and all body functions below the neck. Spinal nerves emerge from the spinal cord through gaps between the main body of the vertebrae and the facet joints. One frequent cause of back pain is a worn facet joint, which can result in a pinched nerve. Therefore, it is very important to keep your vertebrae in good shape.

This drawing shows a normal disc. The main function of your discs is to act as shock absorbers and provide separation between each vertebrae. The outer layers of your discs are formed from tough cartilage. The inner core of your disc is a jelly-like nucleus.

In total, your discs account for one-quarter the length of your vertebral column- 4.50" to 6" (12 to 15 cm) for most people. The disc acquires its nourishment through fluid-attracting and fluid-absorbing qualities of its jelly-like nucleus.

With no blood supply of its own, the disc is dependent on sponge action for attracting and absorbing nutrients from adjacent tissues. During non-weight bearing activities (sleeping) the discs expand as they soak up fluid, increasing the length of the spine by as much as one inch overnight. During weight bearing activities (sitting, standing, exercising), this fluid is squeezed back into the adjacent soft tissue.

Your vertebra are supported and moved by many different muscles. Muscles are used for three basic functions; support, movement, and posture control. If muscles are tight or weak, they create or worsen back pain. Joints are controlled by at least two sets of muscles, flexors which bend the joint, and extensors which straighten it. In addition, most joints have rotator muscles that twist and rotate your bones. Good posture is only possible if the flexors, extensors, and rotators are in proper balance.

Your paraspinal muscles (which run parallel to your spine) rotate your spine, bend it backwards, and sideways, and influence posture by creating and maintaining the curves of your spine. Your erector spine muscles are involved in movement and run the length of your spine. These muscles help you to bend over by resisting the force of gravity, and to straighten up by contracting and exerting great compressive force on your spine.

Your abdominal muscles play an important role in helping to support the spine by maintaining pressure inside the abdomen. This pressure is an essential measure of counter support to the spine.

Your psoas muscles (hip flexors) are a large group of muscles in the abdomen. These muscles help to flex your hips when walking or climbing stairs. They play an important role in maintaining posture for sitting and standing.

Intravertebral joints are supported by ligaments, tough and inelastic fibers which support the spine and hold it together by allowing only a limited range of movement in any one direction. Ligaments require regular movement and loading, otherwise they will eventually become stiff and weak.

Summary

• There are 24 vertebrae in your back which encase your spinal cord.
• Spinal nerves run through each vertebral joint in your spinal column.
• Your discs act as shock absorbers.
• With no blood supply of their own, discs depend on sponge-like action to soak up nutrients.
• Muscles and ligaments require regular movement in order to maintain flexibility.

Click Here for "The Low-down on Gravity" - Information about how your back is affected by gravity.