According to Which?, 80 per cent of us will suffer from back trouble at some time in our lives. Driving is widely blamed. Spend more than half your working day at the wheel and you are six times more likely than non- drivers to be off work, according to a survey by Loughborough University. In another study, lorry drivers were found to be 25 times more prone to a slipped disc.

So what's wrong with our car seats? Have the manufacturers got them wrong? John Gorman, of Iliac Design, believes they have. "All cars seats are designed on completely the wrong principles," he says.

Gorman - a chartered engineer before he became a qualified chiropractor and seat maker - argues that modern car seats with fashionably prominent lumbar support, widely regarded as good for the spine, exacerbate back trouble. Gorman, who self-healed his own sports-aggravated back problems, asserts that lumbar padding causes the backbone to bend more, not less, just above where it connects with the pelvis. It is here that most serious back trouble occurs.

It was obvious to Gorman, as a mechanical engineer, that lumbar padding was not the answer. In countering the pelvis's natural tendency to tilt backwards under body weight when sitting upright - as in a car or at your desk - the backbone levers itself into a double bend, opening up the base joints. The greater the angle between each vertebra, the greater the strain - and the higher the likelihood of back trouble.

Using computer graphics, this harmful effect is clearly illustrated in an Iliac video. It also shows that those postures regarded as correct - sitting up straight and not slumping - defy nature. Relaxing with an evenly curved spine, as in squatting on your heels or slouching in a chair, is good for your back. It's no coincidence that lower back trouble is rare in third-world countries where there are few drivers or office workers.

Gorman's solution to the problem is simple. Do away with the spine-distorting lumbar padding and provide instead firm support for the tall sides of the pelvis.

Iliac Design's 'pelvic posture' seats (those for office use are already in production) are quite distinctive. The pelvic support bulges low down in a sort of vee formation at the base of the backrest. Little or no pressure is applied to the lumbar region just above.

I tried two of Gorman's experimental pelvic seats. That in a Citroen Xantia had particularly prominent V-shaped pelvic padding. The benefits were soon apparent. The pelvic support in a Nissan Serena (Gorman's family wheels) was not so prominent but no less effective. Both seats felt anatomically right.

Iliac reports favourable reactions from most drivers who have tried its seats. Pending the availability of car seats built to his pelvic posture principle, Gorman recommends portable padding - and plenty of slouching and crouching, just as nature intended. If your car has adjustable lumbar support, set it to the minimum.