A back injury does not usually result from one isolated incident. Your back's wear and tear prior to the injury determines the damage's extent. Over a lifetime, many minor stresses or irritations add up, gradually weakening and stiffening your spine, setting you up for a significant injury. Many doctors agree that main causes of back pain include:
To understand just how dramatically gravity affects your spine, try this exercise at home:
Measure your height in the morning, and then again at night. You will be .5 to .75 inches shorter at the end of the day, all due to the compressive effects of gravity on your spine. During weight-bearing activities (sitting, standing, exercising), nutritive fluid gets squeezed from your discs and into the adjacent soft tissue. This significant loss of moisture results in height loss by the end of the day!
During non-weight bearing activities (sleeping), the discs expand as they absorb fluid, healthfully increasing the length of the spine. However, you will not gain back the full extent of the height potential. Thus, as a baby your discs are 90% water, but by the time you reach 70 years of age, your discs are only 70% water! Taken over a lifetime, this loss of moisture causes thinning discs, and your height will shrink .5 to 2 inches!
Thinning discs would be more tolerable if height-loss were the only effect. Yet, thinning discs also results in worn facet joints due to increased pressure. The joints can quickly become painfully irritated and inflamed, with the lubricating fluid which surrounds each joint swelling and pressing on a nerve root.
How do various activities affect the amount of pressure on your discs?
Your daily routine (running, sitting, lifting objects) along with the force of gravity places pressure on your discs. For example, sitting creates 50% more stress on your discs than standing. Sitting while leaning forward (i.e., typing at a computer) puts an extraordinary 150% more pressure on discs than simply standing does. The average person spends 16 hours a day (over time, 2/3 of one's life) sitting or standing.
How do we know that gravity is a major cause of thinning discs?
We know because astronauts grow in space! After 84 days in space (a gravity-free environment), astronauts grew 2 inches in height. During these 12 weeks in orbit, their discs had continued to take moisture from the blood stream and adjacent muscles, but with no gravitational pull squeezing it back out, the discs remained healthfully thick, lengthening the astronauts' spines, and so making them taller. In fact, space suits are designed to fit the extra 2-inch spinal stretch. After a few days on earth (a gravity environment), the astronauts returned to their normal height.
How can inversion reduce the effects of gravity?
When you invert, your body can stretch up to 2 inches over a short time. "Muscles relax quite quickly in the fully inverted position, and the length of the spine measurably increases after only a few minutes. Some of the lengthening effect is gained from reabsorption of fluid into the center of the disc. Used over a longer period, this may delay the degeneration process that occurs due to 'drying out'" (Beating Back Pain, Tanner).
Weak back muscles
Estimates place 60%-70% of all back pain as resulting from muscle strain.
Your musculo-skeletal system needs a basic amount of strength and stamina in order to protect itself against back pain. In turn, your muscles require a good supply of blood and energy in order to perform and protect at peak performance. Poor posture or muscle spasms can deprive back muscle structures of much-needed blood and oxygen.
For example, sitting and bending forward (i.e., typing at a computer) creates inactivity in two of the three muscle groups which support your back (abdominal and hip flexors) and, therefore, detrains and weakens important protective systems. If this posture continues, muscles become painful, weak, inelastic, and shortened.
Often, joint-muscles are imbalanced. For instance, the flexors may be tauter and shorter than the extensors, such that the joint cannot fully straighten; or, the rotator-muscles in one direction may be stronger than those in the other direction (i.e., from one-sided sports like golf). These unequal forces weaken the joint, making it vulnerable to injuries. This imbalance can cause pain.
Inversion can help
Inversion gently stretches your back muscles, helping to increase the supply of blood and oxygen to your back muscles. With a regular inversion program of stretching and strengthening, the muscle groups can be balanced, keeping your back protected.
Muscles and ligaments require regular movement, without which becoming stiff and inflexible.
As you age, your discs become thinner, straining the intervertebral joints and creating pressure. The ligaments which used to firmly support the spine become slack, and joints considerably loosen. It is comparable to a worn machine with a loose drive-belt or pulley, where any undue strain risks throwing something out of alignment. Throughout your life you create muscle stress by bending the spine too far, placing too much pressure on the spine while bent, or bending too repeatedly.
Ligaments have a limited blood supply and, as a result, heal slowly. Sometimes they simply fail to heal completely, leaving scar tissue. Scar tissue is weaker and less flexible than regular tissue, and leaves the area stiff and vulnerable. This is how your back ages and becomes more inflexible. Without consistent stretching, ligaments stiffen and may increase the risk of painful injury.
Inversion can help
Unless you perform appropriate exercises to restore normal flexibility, the unhealed tissue may produce a perpetual source of back pain and/or stiffness. Simple, gentle stretching can aid scar tissue's flexibility and strength, or even allowing the tissue's absorption and replacement by more normal ligament and muscle tissue. This strengthening can assist in preventing a re-injury. Although there are exercises that stretch parts of your back separately, inversion gently stretches all of the protective ligaments at once.