One of the pioneers in proposing the benefits of a forward-sloping seat was Danish surgeon Dr. A.C. Mandal. He had found that the only way he could remain seated without incurring backpain was to lean forward on the front legs of his chair. He also observed that many school children did the same thing when trying to ease back pain brought on by poorly designed school furniture.
Mandal recommended that the seat pan should slope forward by 15°. When we take up this position our lumbar spine does not need to flatten out to assume the seated posture and our hips and trunk are at the optimum position of balance for the muscles.
By tilting your seat forward you alter your centre of gravity from behind the sitting bones (ischial tuberosity) to directly above them. As a result your muscles do not have to tense up or contract to maintain an erect posture. At the same time the lumbar curve ( or lordosis) is restored and pressure on your discs is reduced.
A variation on the forward-tilt seat has been produced which copies the shape of a saddle. This has the effect of opening out the thighs and giving more stability to the pelvis. It also restores some lordosis to the lumbar spine. There are versions of this type of seat on the market which are popular with some people. One drawback of this type of seat, however, is that your desk has to be set up much higher to allow for the legs to occupy the “saddle position.”
Some of the more common objections to early versions of the sloping seat were:-
You tended to slide forward.
Too much weight was placed on the feet.
Your clothes tended to ‘ruck up’.
The Balans was one of the first forward-sloping chairs in mass production to incorporate Mandal’s suggestions – using a knee rest to prevent slipping forward.
Most of the weight is taken on the knees and while this reduces pressure on the discs, the muscles had to work harder to maintain an erect posture since there is no backrest. As your muscles become tired there is a natural tendency to slump.
In addition to these problems your knees and shins can become quite sore after a time since there is no provision for changing the knee position. Getting in and out of the chair is somewhat difficult because of interference from the central pillar.
Despite the various drawbacks mentioned, however, many thousands of these chairs were sold because of the obvious relief given to the discs through the forward-sloping seat taking pressure off the spine.
Kneelsit balance chair
When you allow the seat pan to tilt forward your pelvis rotates forward, this posture produces the least amount of stress on muscles, tendons and discs, since your spine is correctly aligned.
When your pelvis is tilted forward your lumbar spine curves naturally and the rest of your spine follows. This is the ideal posture when working upright – as at a computer. When you have a backrest – as in the Kneelsit chair – this backward tilt can also be used to relax the spine and take pressure off your disks and muscles, for example when you are reading or just chatting.
The real secret, however, to maintaining a healthy spine is to have a chair which allows free-flowing, natural movement between both forward and backward tilts. This sets up a continuous “pumping action” which feeds and nourishes the cells of your spinal discs, exercises your back muscles and allows you to sit for hours on end with very little discomfort.
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