How back supports work

Back supports work by improving the shape of the spine when sitting - by correcting a slouched or slumped posture, stress in the back is reduced and the whole body fits the seat better.

In the sketch, you can see that without back support...

1. The spine is bent in a banana shape, with the pelvis pushed forward.
2. The weight of the chest and head is in front of the spine, increasing its tendency to bend.
3. The "sit bones" under the pelvis, which take most of the weight, are a long way in front of the spine, so
4. the pelvis tends to rotate backwards.
5. This tends to slide the legs along the seat cushion, making your posture unstable and creating a vicious circle as the pelvis rotates more.  Also the skin under your thighs and buttocks is being dragged, which research shows makes it 50% less able to cope with the weight on it.
6. As the pelvis rotates, the tailbone (coccyx) is moved underneath and the tip can be loaded painfully in bend on the seat cushion.
7. The buttock muscles also move underneath and the constant pressure on them inhibits their blood supply - giving "numb bum".

In this sketch of an ideal posture...

1. The supported spine is in its "S" shape
2. with the weight of the torso going through the lower spine so that it is in balance.
3. The line of the spine is much closer to the sit bones,
4. reducing the tendency of the pelvis to rotate backwards.
5. In turn this reduces the tendency of the legs to slide along the cushion, so the posture is more stable and the skin is not being dragged.
6. The tailbone is more upright away from the cushion, and
7. The buttock muscles are withdrawn behind the pelvis instead of being underneath.

In addition of course there are great improvements in the area of the spine itself - the shape of the discs and their internal pressure (which affects their nutrition), pressures on the spinal cord, and strain on the back muscles and tendons.

In practice it is unrealistic for most of us to try to sit so perfectly, the hamstring muscles are not kept that flexible and it feels very unfamiliar, but a straight spine is achievable, and will still give the same benefits, just to a lesser extent.  BackShape caters for this real-world compromise by being compressed in use to about half its thickness.

Most back problems are a result of stress outstripping recovery over a long period of time.  By making your sitting time less stressful for your back, correct back support turns sitting time into recovery time. It's a crucial difference.