Back pain will affect six out of ten of us at some time in our lives - and it can be crippling. To mark Back Pain Week STEPHEN LEWIS looks at how to avoid problems with your back.

FRANCIS Chapman had always been fit and active. So when he began to experience a pain in his leg, the 50-year-old self-employed design technician assumed it was just a minor muscle problem and ignored it. "There was no obvious cause for it," he says. "I hadn't fallen off a wall, or anything like that." But the pain didn't go away. In fact, it got progressively worse.

As you do, he sought for an explanation. At one point he even threw away all his underwear, thinking it might have shrunk in the wash and be constricting his leg.

Oddly enough, the strategy didn't work. "Your logic does get very skewed," he admits, with a sheepish grin.

Like many people, Francis was reluctant to go to see a doctor. "I think it's maybe more typical of the older generation," he says, "but you think, unless there is blood, what do you go to the doctor for? There's nothing to see."

Eventually, though, the pain got to the point where he could no longer deny it. He was walking twisted to one side to favour his painful leg.

He went to see his GP, who referred him to York District Hospital. It emerged there was nothing wrong with his leg at all - the problem was with a lumbar disc at the base of his spine.

A cycle of treatment and physiotherapy got rid of the pain and restored his mobility. Gingerly at first, then more confidently, he began to resume an active life. Until one day, while raking and sweeping the gravel paths of his home near Stamford Bridge, he felt a twinge again.

He stopped immediately: but the damage had been done. The pain developed until he could barely move.

"It was quite fierce," he admits. "I'd never suffered anything like that in my life. It developed to the point where I was waking up and wondering whether I was even going to be able to get out of bed in the morning."

This time, X-rays revealed he was suffering from wear and tear of bone in his lower spine. Again, with treatment and physiotherapy, the symptoms were brought under control. A regime of morning exercise devised by physiotherapists helps keep his back supple: but he's uncomfortably aware his pain could return at any time.

"I fully expect it to," he says, "though I'm working hard to try to make sure it doesn't. But I wish now I had gone to see my doctor a bit earlier that first time. I just didn't recognise the symptoms. I had leg pain, not back pain."

Francis is far from alone with his back problems. York District Hospital physiotherapist James Midgley says back pain is increasingly common and is one of the main causes of disability.

Cases dealt with by outpatients alone have increased five fold in the past ten years, he says: possibly because of our more sedentary lifestyle.

The good news is you can take steps to help prevent it.

Listening to pain is one precaution. "Pain is a warning," James says. "It is a mechanism telling you something is wrong."

James says if Francis had sought medical help earlier, the damage to his back may well have been less severe.

Other things that can help include regular simple exercise, a good, upright posture - "imagine you have a wire attached to the top of your head pulling you taller", says James - a supportive mattress and taking care when lifting. "No sensible person crosses the road without first checking for traffic," he says. "Why not be sensible about your back and avoid accidents and injuries? Having a bad back is miserable and can ruin your life."

Ten top tips to feel tip top

Here, with thanks to James and to the No-nonsense Guide to a Healthy Back, by Garry Trainer and Tania Alexander, are our top ten tips for avoiding back pain

n Keep active and try to exercise regularly. This will strengthen muscles which support the spine

n Stand up straight: slouching puts a strain on your back

n Slumping in front of the TV or sitting at a desk all day can cause back problems. Get up and stretch regularly every 20 to 30 minutes

n If you work at a PC, check your chair and desk are at the right height. Legs should be bent at 90 degrees when sitting

n Make sure your mattress is supportive

n Don't leap into unaccustomed activity such as digging. Do some simple stretches to warm up first - then take regular breaks.

n Use long-handed implements where possible when gardening to avoid bending and stooping

n Take care when lifting. Bend your knees, rather than your back, and avid twisting

n When answering the telephone, avoid crooking it between your head and neck

n Don't cross your legs: this restricts circulation and puts your spine out of alignment