TOO MUCH SITTING – A HEALTH HAZARD
Although sedentary work may appear as very comfortable and harmless, spending too much time in your chair (or on your couch) can also harm musculoskeletal conditioning, particularly when it comes to spinal health.
With prolonged sitting musculoskeletal system is strained by unergonomic body posture, physical inactivity, long-term static loads and reduced blood flow. Spine is one of the most affected part of it.
Musculoskeletal overload results as unpleasant sensations, pain, numbness and tingling, at first transient and fleeting, but can become chronic with long-term neglect.
PARTS OF THE SPINE
Spine is your body’s central support structure. It is made of vertebrae (small bones) that form the spinal canal. Between each vertebrae sits disc, tough on the outside with a softer, gel-like fluid inside.
The spinal canal is a tunnel that houses the spinal cord and nerves, protecting them from injury. The spinal cord is a column of nerves that travels through the spinal canal. The cord extends from the skull to the lower back.
Cartilage is a resilient and smooth type of connective tissue and is a structural component of many body parts including the ears and nose (on picture – A), bronchial tubes, ends of the ribs, between the vertebrae in the spine (B) and most important – joints between bones (C), with primary purposes to act as a shock absorber and to allow smooth movement of the bones.
Cartilage is avascular. Since there is no direct blood supply, it receives nourishment via diffusion from the surrounding environment. The compressive forces that regularly act on cartilage also increase the diffusion of nutrients.
This indirect process of receiving nutrients is a major factor in the slow turnover of the extracellular matrix and lack of repair seen in cartilage. Therefore exercise is beneficial for joint health as enhances production of matrix molecules, which can have a positive effect on joint health.
An intervertebral disc lies between adjacent vertebrae in the spinal column. A vertebral disc is the shock-absorbing structure between each vertebra. The disc has a thick outer layer (annulus) that surrounds the soft gel-like center (nucleus).
Intervertebral discs act as cushions in between vertebrae. The spinal canal, containing the spinal nerves, lies directly behind the disc and the vertebral bodies.
With increasing age, injuries, long-term physical loads and other degenerative processes the nucleus generally becomes more fibrotic and less gel-like, which has a major effect on the disc’s load-bearing behaviour. Lower water content causes loss of height and the discs tend to bulge. Such major changes in disc behaviour have a strong influence on other spinal structures, and may affect their function and predispose them to injury.
NUTRITION OF INTERVERTEBRAL DISCS
NUTRITION OF INTERVERTEBRAL DISCS
Similar to other articular cartilage, intervertebral disc receives nourishment with diffusion from the surrounding environment. Therefore movement in the spine is crucial to maintaining the health of the intervertebral discs and the spine.
Spine activity changes intradiscal pressure. Fluid containing nutrients and waste substances is squeezed out and absorbed. During forward bending, the pressure increases in the front part of the plate and falls in the back part; the reverse is the case with backsliding. The principle is the same for other movements in the spine.
Nutrition of the intervertebral disc – video
STRAIN ON THE SPINE
LOADING OF THE INTERVERTEBRAL DISCS
Forces acting on the intervertebral discs are greatest in the lumbar and sacral parts of the spine. While standing the pressure on the intervertebral disc, which lies between the 4th and 5th lumbar vertebrae (“L4L5″ disc) is approximately equal to our body weight.
Long-term loads in the spine can result in herniated or prolapsed intervertebral disc. In these cases the discs shrink in height, bulge out into the surrounding spinal canal and press on the nerve roots (see picture). Depending on where the herniated disk is, it can result in pain, numbness, or weakness. Signs and symptoms depend on where the disk is situated and whether the disk is pressing on a nerve.
When talking about herniated disc putting pressure on part of the nerve, sciatica is most commonly known. This causes pain from lower back through the hips and buttocks and down the leg, in severe times numbness and tingling in the affected leg.
Prolonged sitting puts strain on the musculoskeletal system. The consequences can also be manifested as damage to the spine and nervous system.
Regular physical activity and good ergonomics are crucial for the health of the spine and intervertebral discs.