When it comes to finding excuses not to exercise, I could have the perfect passport to couch-potato land. Pounding the pavements leaves me hobbling like a twisted marionette thanks to the six pins in my left knee after a cruciate ligament replacement operation 15 years ago, when I was 18. And I have to juggle the demands of two young children with an increasingly demanding work schedule.

Cycling seemed to be the answer: low-impact and good for the environment. It was easy at first, but after only a month of doing five miles to and from work each day and a two-hour ride at weekends, I started developing a tightness in my upper and lower back as well as my hamstrings. The only way of dealing with the aftereffects of each ride was to resort to painkillers.

Clocking up injuries

To judge by a 1994 study in the International Journal of Sports Medicine for which 518 recreational male and female cyclists were questioned, I am not alone. The California State University researchers found that 85 per cent of cyclists, clocking an average of 75 miles a week, suffered from one or more overuse injuries. Of those studied, 48.8 per cent reported neck problems, 41.7 per cent knee trouble, 36.1 per cent groin and buttocks strains, 31.1 per cent wrist and hand pain and 30.3 per cent backaches.

Perhaps most worrying was that while 440 of the cyclists were experiencing some degree of pain after spending hours hunched in anatomically incorrect postures, only 36 per cent had sought medical treatment. So when I was offered the chance to trial a new bike-fitting system by the bike manufacturer Specialized, which will be on sale soon through 25 of its stockists, I grabbed it with both hands.

“Most cyclists think you can just jump on a bike and go, when that's far from the case,” explains Dr Michael Lanning, a Harley Street chiropractor who specialises in cycling-related joint and spine injuries. “If your bike is not set up correctly for your body shape, there's a high likelihood that you'll suffer long-term injuries, especially if your body's not conditioned for cycling. You're putting potentially huge strains on all your main joints.”

Since 2000 there has been an 83 per cent rise in the number of cyclists on the roads in London, and an 187 per cent increase in the number of cyclists using the National Cycle Network in the same period, according to the cycling charity Sustrans (www.sustrans.org.uk). However, Lanning says that the number of cyclists coming to see him with overuse injuries is spiralling out of control.

“In one hour you can pedal up to 5,000 times, so any kind of misalignment will quickly present problems,” he says. “When problems arise, they can take months of agonising pain to diagnose and sort, and the whole process is often completely avoidable. In many cases it can be as simple as adapting the bike so that the saddle and the handlebars are at the correct height for your frame.” And the advantages of being properly fitted to your bike don't stop there. “The more comfortable it is, the more likely you are to keep on riding,” says Lanning, “while it also gives you more control and power, making you a safer rider.” His advice made me realise that my bike set-up and frame could be causing my troubles.

Fit the bike to the rider

The BG FIT system from Specialized has been honed from more than 30 years of analysing thousands of cyclists, from humble commuters to pro-road and mountain bikers. It was developed by Dr Andy Pruitt, the director of the sports medicine programme for the United States Cycling Federation and American Olympic Cycling Team. Lance Armstrong, the seven-time winner of the Tour de France, and the world champion mountain biker Gunn-Rita Dahle Flesjå say that Pruitt's know-how has kept them injury-free.

I started with a two-hour session with James Booth, the UK's first BG FIT technical fitter at Specialized's UK headquarters in Chessington, Surrey, who has trained with Pruitt over the past two years. It demonstrated the attention to detail of Pruitt's approach. First came a question-and-answer session to determine my goals, aspirations and past injuries. Then every aspect of my flexibility was assessed- hamstrings, hip flexors, ankles and the crucial iliotibial band that runs down the outside of the leg, stabilising the knee during cycling.

“The most common misconception among cyclists is that because you're a certain height, or if you've got a specific inside leg measurement, you need a certain set-up,” Booth explains. “The bike has to be fitted to the cyclist, not the other way round, and that has to take into account your flexibility, injuries and comfort; the old-style thinking of simply measuring a distance from the cross-bar to your crotch, or trying to emulate the position of pro cyclists you've seen on telly, just doesn't work.”

Booth assessed my pelvis, spine and shoulder blade alignment and mobility, my foot arch fall and any leg length discrepancy (it was Pruitt who first diagnosed a significant leg length difference in Eddy Merckx, arguably the greatest cyclist in the modern age). So far, so good, Booth said.

After 50 minutes of pushing, pulling and prodding, I was allowed on to my bike that I had brought with me. It was held upright firmly in a roller system so I could be analysed “dynamically”; that is, while cycling. “For any assessment to be accurate, it has to observe you while you're in motion,” Booth says. “It's this 3D approach that really sets this system apart.” And it was here that my problem was pinpointed.

While cycling in what I felt was a comfortable position, Booth noticed my pelvis rocking from side to side, as a result of my saddle being too far forward. So too much pressure was being placed on my lower back and my knees weren't correctly placed to optimise power.

Bye-bye paracetemol popping

Using a goniometer - an angle-measuring device - and a series of plumb-lines to measure the angles at every point of my body through every degree of rotation of the cycle, he slowly tweaked each nut and bolt on the bike, replaced the handlebar stem for a shorter one and two hours after I had walked into his fitting room, asked how I felt. “Like this is a different bike,” was my short answer.

According to Booth, my saddle had been tilting too far forward and was too high, my handlebars were too low, too far away from me and rotated at the wrong angle. The frame, he said, was fine; it was the incorrect initial set-up that had put too much pressure on my lumbar spine and knees. “Until you know how it's supposed to feel, most riders assume you have to get used to your bike, and put up with a certain amount of discomfort, which is rubbish,” he says. The good news for regular riders wanting to take advantage of the new system is that no matter what brand of bike you ride, the Specialized fitters can make all the necessary adjustments.

That evening I rode the bike for 45 minutes and felt blissful relief at both the ease and comfort of the journey. Two months on, my days of paracetamol-popping are long gone, as is the feeling of dread each time I approach my bike ready for the next outing. I'm gratified to learn that two of the first people to snap up the new UK bike fitting system are the sporting legends Martin Johnson and Alan Shearer who recently cycled from Newcastle to London to raise money for Sports Relief, both of whom are suffering knee problems but still want to stay in shape.

“There's no doubt that there is a huge market for cyclists wanting to get the most from their bikes,” Lanning says. “The trouble is going to be convincing cyclists that they're missing out until it's too late.”

On your bike

For more information on Specialized's BG FIT system (which costs £120 per session, no matter what brand or type of bike you ride) visit www.specialized.com

Lancashire

Paul Hewitt Cycles, Leyland, www.hewittbikefitting.co.uk, 01772 424773.

Designed to maximise power and comfort for serious riders. Costs £50 for a 45-minute session, refundable if you buy a bike.

London

Cyclefit, Covent Garden, www.cyclefit.co.uk , 020-7430 0083. Full assessment and fit (including filming you on a specialist test bike) costs about £150 for three hours.

Gloucestershire

Kinetic-One, Stroud, www.shop.kinetic-one.co.uk , 01453 752253.

Full bike fitting, including video analysis and wind tunnel testing. From £400.