How our discs work to gain nourishment
Conventional, ergonomic chair designs are still, unfortunately, one of the major causes of back pain & poor posture. If you understand how your spine works, however, this may help you in the important task of correcting and improving your posture and keeping your spine healthy
Discs are gel-like bodies which perform a very important role in helping your back work efficiently. One of their principal functions is to act like shock absorbers and insulators between the blocks of bone (or vertebrae) which go to make up your spine. Not only do your discs have to cope with constant pressure, they also absorb shocks, compression and twisting stresses and have to allow limited movement of the spine.
Your discs are always under constant pressure. In the early 1970's Professor Nachemson of Sweden measured the pressure in the lumbar discs of a group of "volunteer?" students. It was found that even when you are lying down there is still considerable internal pressure. When sitting and particularly when sitting and leaning forward without back support, the pressure increases markedly. In other words more muscles are working and further compressing your spine when sitting than when you are standing upright.
The reasons why there is constant, internal disc pressure are as follows:-
A column of blocks of bone separated by elastic mobile joints would tend to be unstable and flop about. To add the necessary stability these blocks of bone (vertebrae) are joined to each other by strong semi-elastic ligaments.
Because these ligaments are under constant tension they impose a compression force on your discs.
To balance this force there must be some way of maintaining pressure inside your disc otherwise it would collapse. To understand the source of this internal pressure it helps to know something about -
How your discs get nourishment
- Chemical structure of your discs are about 85% water and contained mainly in the central core or nucleus. Within this fluid are the specialised cells called 'chondrocytes'. Their function is to manufacture a chemical compound known as proteoglycan - the principal ingredient of the 'lubricant' that allows our joints to move freely. Chondrocytes are living cells and, like all other living cells in your body, require regular nourishment and a means of ridding themselves of waste products.
Unlike the majority of other cells, however, your chondrocytes cannot receive nourishment from the blood supply because of the extreme pressures under which they operate. They use instead a unique system of movement which helps maintain the different electrical potentials - drawing in oxygen and pushing out waste products.
The outer walls of the disc and cartilage end plate act as a sort of selective sieve (semi-permeable membrane). This allows water and chemicals to pass through, including those chemicals necessary for your chondrocytes to function. At the same time waste products of this process pass out.
At the centre of the disc the concentration of essential nutrients is only just great enough to maintain your chondrocytes in reasonable health and the waste disposal action is only just coping. Without adequate diffusion, assisted by movement, the chondrocytes can easily become starved.
Movement is the most effective aid to this diffusion. Your discs were designed for those times when we were more or less always on the move. Now, you may be starving your chondrocytes by staying in one position too long, whether sitting, standing or lying down.
The unique features
of the Kneelsit chair combine to induce balanced movement, nourish your spinal discs, enhance posture,
reduce the pressure on your spinal vertebrae and diaphragm, relieve tension
and improve your breathing capacity and alertness - -so producing a genuine
sense of poise and equilibrium.
Gregory. J. Usher. B. Ec., Dip. Ed., F.A.I.I., M. Psych.
(1) Fisk J. W. (1987) "Your Painful Neck & Back
Swan R. C. (1960) "The Therapeutic Value Of The Rocking Chair
Dickinson J. (1974) "Proprioceptive Control of Human Movement
(4) Clarke D. L. (1977) "Vestibular Stimulation Influence on Motor Development
Milner P.M. (1971) "Physiological Psychology",
Sherrington C.S. (1906) "The Integrative Action of the Nervous System"
Weiss B. (1954) "The role of proprioceptive feedback in positioning response.
"I am on a computer nearly 8 hrs a day and have ALWAYS found
customary chairs just this side of objects of torture -- and, have spent a
great deal of money on various types/brands of chairs. I do not have a 'bad
back' or medical situations for which I am trying to compensate. I just want
to feel not abused at the end of an 8 hr day (which is really 10+ hrs.). I
achieve this with the Kneelsit. The first couple of days of becoming acquainted
with it, I found it comfortable, flexible, and surprisingly easy to manuver
around. Now it is part of my 'day' and a part that does not exhaust me in
trying to stay comfortable! It is well worth the money -- which, I might add,
is less than a standard chair that we recently bought. I highly recommend
Adustable Seating P.O. Box 253 KIAMA N.S.W. 2533 AUSTRALIA