Posture and Pain

The human body was designed for movement, but industrial and technological advances have done much to slow us down. With the the Industrial Revolution, increasing numbers of workers performed relatively stationary tasks. With the advent of computers, the number of sedentary jobs has increased, as have the number of musculoskeletal disorders. One study (Pope M. Muybridge lecture. In: Proceedings of the International Society of Biomechanics XIVth Congress. Paris, France. July 1993.) showed the prevalence of low back pain has increased by 2,700% from 1980 to 1993.

Changes in the way we use our bodies has contributed to a dramatic increase in work related pain. Basically, the body must move and move properly to stay healthy. According to a study (Patel AV, Bernstein L, Deka A, et al. Leisure time spent sitting in relation to total mortality in a prospective cohort of US adults. Am J Epidemiol. 2010;172:419-429), women who sit more than 6 hours each day have approximately a 40% higher death rate and men a 20% higher death rate than those who sit less than 3 hours a day. This is not good news for those of us who tend to sit most of the day.

When you sit in a static posture without leaning on your chair's backrest, more than 50% of your body's muscles must contract to hold the body motionless while resisting gravity. The static forces resulting from these prolonged, static postures are much more taxing on the body than dynamic or moving forces.

Prolonged, static postures, whether standing or sitting, result in microtrauma including muscle imbalances, muscle ischemia, trigger points and disc degeneration. This microtrauma develops through a series of events which can progress to pain or a cumulative trauma disorder.

Prolonged, static posture leads to muscle fatigue or muscle imbalance. This leads to substitution of normal muscles and problems within the muscles, such as trigger points and muscle ischemia or necrosis. This leads to pain and protective muscle contractions or spasms. The result is hypomobility of joints, nerve compression, disc herniation and disc degeneration.

Even with the best ergonomic equipment, we frequently find ourselves slightly leaning, usually more in one direction than the other. If you are right handed, you may tend to lean forward and to the right when you leave a neutral posture. Over time, the muscles can adaptively shorten on one side of the body, spine, or joint. This imbalance can result in asymmetrical forces causing misalignment of the joints with loss of range of motion in one direction over the other. Over time, the body's muscles can adapt to the abnormal posture caused by these muscle imbalances and tend to maintain this unbalanced posture not only at work, but in leisure activities as well.

Maintaining static postures requires sustained muscle contraction. When a muscle is contracted for a prolonged period of time, muscular pressure rises. This pressure compresses the blood vessels within the muscle, and during contractions, can obstruct blood flow through the muscle. A substance called lactic acid accumulates resulting in muscular pain and fatigue. Even in the best working postures, our bodies perform static muscle work. Dynamic muscle work, on the other hand, creates a healthier environment for bodily repair. The rhythmic, pump-like contraction and relaxation of the muscles ensures adequate blood flow and oxygen to the muscles, as well as lactic acid removal. Recovery time from low level muscle fatigue after working all day is very slow and there is a risk that muscles may not even recover by the following workday. Human muscles are not designed for continuous, long lasting contractions. They require rest periods to recover from even low level exertion. If the rate of tissue damage exceeds the rate of repair due to insufficient rest periods, muscle damage or cell death (necrosis) can result.

A trigger point is a group of muscle fibers that are in a constant state of contraction. They feel like a hard knot, nodule, or small pea. When pressed upon, they may be painful locally or refer pain to a distant part of the body. They neither allow the muscle to contract nor relax properly and decrease flexibility and range of motion. Trigger points may be active (painful) or latent (causing stiffness and restricting range of motion). Because they are caused by prolonged muscle ischemia (lack of oxygen), posture alterations and mental stress, it is easy to see why trigger points are so common.

By adulthood, there is no blood supply to the inside of your spinal disc, and its only means of nutrition is via imbibition. Think of the disc as a sponge. At rest, it absorbs no water; however, when compressed and released, it imbibes water. This is similar to the mechanism of the spinal disc. It requires alternate compression and relaxation to stay healthy. Sustained contractions in the muscles as during active sitting also reduce disc nutrition by compressing the discs, increasing intradiscal pressure. In the lower back, disc pressures are generally higher when sitting than when standing. Compared to standing, lumbar disc pressures increase by 40% when you sit "actively" (without leaning on a backrest), and by 200% when sitting and leaning forward 40°.

Movement is imperative to decrease the structural damage from prolonged, static posture. You can incorporate the Active Seat to help with movement strategies to help you move the workload from one group of muscles to another, prevent painful muscle ischemia, and reduce static spinal disc loading.

It is important to try and keep and maintain proper sitting posture, not only while sitting at a computer, but at leisure time. This is important for back posture and neck posture.

Taking a small break and stretching can help. You can find sources for a back stretch and neck stretch while sitting. The benefits of stretching are numerous and include: increasing blood flow to muscles; increasing production of joint synovial fluid; reducing the formation of trigger points; maintaining normal joint range of motion; and increasing nutrient supply to spinal discs. It is important to keep in mind some general advice for stretching:

• Assume the starting position for the stretch
• Breathe in deeply and exhale as you slowly increase the intensity of the stretch up to a point of mild tension or discomfort
• Hold the stretch for 2 to 4 breathing cycles (10 to 20 seconds)
• Slowly release the stretch—come back to neutral position. Repeat the stretch, if time allows.
• Try the stretch in both directions, and determine which side is tightest. Perform the directional stretch primarily toward the tightest side throughout the workday, and place stretching charts where you can easily reference them.
• Never stretch in a painful range. If stretching increases your pain, stop immediately.

Stretches can be performed every 45 to 60 minutes throughout the day, taking advantage of 10 to 20 second microbreaks throughout the workday.

Implement movement prevention strategies to ensure a high quality of life, prevent disabling injuries and extend your career.