Read an Excerpt
The back is the one ofthe most complex and versatile parts of the human skeleton. The key to many of your vital functions (see box, right), it has great strength and flexibility. However, this means that great demands and stresses are placed on it during your daily activities, making it one of the most vulnerable parts of your skeleton. As many of you will already know, it is, therefore, an all-too-common site for aches and pains.
Pain is your body's way of telling you that something is wrong. When you have back pain, you experience a sensation generated by the brain in response to signals from pain receptors in your skin, organs, muscles, and other tissues. The intensity of the pain you feel is not due to the strength of such messages, but rather their number and frequency.
ACUTE VERSUS CHRONIC PAIN
Pain messages are of two natures: acute and chronic. "Acute" travels at 10 meters (30 ft) per second, while "chronic" travels at only about 1 meter (3 ft) per second. Acute pain is the more intense of the two as more acute signals than chronic ones can be sent in the same length of time.
Acute pain in the back is usually specific with a recognizable cause (see page 9) and a particular treatment. Chronic pain (see page 10-11), however, can be difficult to explain even a medical examination can reveal nothing amiss. This is because even very minor damage to the joints, muscles, ligaments, and nerves of the spine can cause pain. The exercises and advice in this book will guide you in how to alter your lifestyle in order to help alleviate chronic problems over time, and prevent any recurrences (see pages10-11).
The spine is made up of 33 vertebrae, although some are fused together so that there are only 26 separate bones. The column is divided into different sections of vertebrae (see below). Understanding how your spine functions will help you keep it in healthy, working order.
Vertebrae are connected to their neighbors by two facet joints, and an intervertebral joint. The surfaces of the small facet joints are covered in cartilage and bathed in synovial fluid, which is all contained within a joint capsule. The fluid in the capsule enables the two bones of the joint to glide over each other without friction. Regular, moderate exercise will keep these lubricated.
An intervertebral joint is composed of two vertebral bodies and an intervertebral disk. The intervertebral disk is a pad that acts as a shock absorber, allowing the spine to move, lengthen, and shorten by molding itself into the required shapes. The inside of it -- nucleus pulposa -- is made of a gooey substance that is 85 percent water; while the hard outside-annulus fibrosus -- is composed of rings of tough cartilage. These disks can lose a lot of their fluid during a day's activities, so adequate bed rest must be taken to allow their recovery at night.
SPINAL CORD AND NERVE ROOTS
The spinal cord relays sensory information, such as pain messages, from the body to the brain, which then sends orders back down to the muscles to act. It is part of the central nervous system, and runs from the base of the brain, down the neural canal in the spine, to the lumbar vertebrae. Two nerves branch off the spinal cord between each vertebra -- one on each side. Back disorders that are particularly painful involve the spine pressing on these nerves, or on the spinal cord itself.
The spine is supported and moved by an intricate network of muscles. There are three main layers of muscles in the back. The small inner layer connects each vertebra to its neighbor; the middle layer connects groups of vertebrae; and the large outer layer -- the erector spinae muscles -- connect the whole spine from top to bottom. The large muscles that work the neck and shoulders are known as trapezius muscles. The glutei muscles in the buttocks support the lower back and pelvis.
Muscles always operate in pairs, so for every muscle that contracts -- "agonist," there is an equal and opposite one that relaxes "antagonist." It is the muscles of the abdomen that work in this way with the muscles of the back to maintain the spine's natural curves. There are four main groups of abdominals ("abs") -- the straight abs that bend and flex the spine, two sets of oblique muscles that flex and twist the trunk, and the transverse abs that keep the abdomen's contents pulled in. You should exercise all back and stomach muscles equally so that there is no danger of muscular weakness or imbalance, which can lead to back pain.
Ligaments are broad bands of tough tissue that bind the vertebrae together, allowing the spine to move as one piece. There are two long ligaments, which run down the length of the spine at the front and back of the vertebral bodies, as well as small ligaments binding each vertebra to its neighbors. Ligaments have a poor blood supply, and do not heal easily if strained or torn.
When viewed from behind, the spine is a straight line in the middle of the back. When viewed from the side, however, it should appear curved. The thoracic and sacral vertebrae curve backward. They are known as primary curves as they are present at birth. The cervical and lumbar vertebrae, on the other hand, curve forward, and develop as a baby learns to raise his head, and sit up. It is these natural curves that give your back the ability to maintain your upright stance, as well as the resilience to absorb the downward forces of gravity, your body weight, and the impact from the ground as you walk or run. The single most important way to look after your back is to maintain this natural posture (see right).
If your back is held too straight, or over-arched, the spinal column cannot cope with everyday stresses, and may start to malfunction. This may affect the order in which you should do the steps of certain exercises. Using the points below as a guide, check and see whether you have any postural problems:
- Flat back -- an overly-straight, rigid back.
- Hollow back or lordosis -- an exaggerated concave arch in the lower back.
- Rounded shoulders or kyphosis -- an exaggerated convex arch in the back, giving a hunchback appearance.