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Alex Hutchinson draws on the latest research to answer your fitness and workout questions in this biweekly column on the science of sport.

The question

Will running ruin my knees?

The answer

This is a fear that stops many would-be runners in their tracks and lurks in the back of the mind of even the most experienced runners. Running and injuries go together like shin splints and ice, so it's entirely reasonable to wonder about the prospects of long-term damage.

These fears should be put to rest by a pair of long-term studies due to be published this year.

In next month's Skeletal Radiology, a team of Austrian radiologists presents knee MRIs of seven runners who had taken part in a previous MRI study before running the Vienna marathon in 1997. The use of MRIs offers a significant diagnostic advantage compared to earlier studies that relied on X-rays.

The results were clear: no new damage in the knee joints of the six subjects who had continued running in the intervening decade. "In contrast, the only person who had given up long-distance running showed severe deterioration in the intra-articular structures of his knee," the authors note.

An even more long-term study at Stanford University has been following 45 runners and 53 non-runners since 1984. All had been taking regular X-rays. The latest results, which will appear in a future edition of the American Journal of Preventive Medicine, show that after 18 years, 20 per cent of the runners had developed osteoarthritis in the knee, compared with 32 per cent of non-runners.

These studies raise a possibility that several earlier studies have proposed: Running may help preserve the joints. But that's not a conclusion that can be drawn at this point, says Eliza Chakravarty, lead author of the Stanford study.

"I don't think I would strongly recommend running for the purpose of protecting the knees."

One drawback with both studies is selection bias. The runners in both cases were committed recreational runners who had a history of being able to run without serious problems.

Data for non-runners who are considering taking up running are harder to come by - a gap that was partly addressed by a large-scale study that appeared last year in the journal Arthritis & Rheumatism, involving 1,279 subjects from the famously long-running Framingham Heart Study.

Rather than studying "runners" versus "non-runners" the researchers examined the general study population, looking for associations between exercise (including running) and the development of knee osteoarthritis over a nine-year period. They found no link, suggesting even overweight non-runners can start exercising without putting their knees at risk.

In sharp contrast, though, the American College of Sports Medicine recently reported that each additional pound of body mass puts four extra pounds of stress on the knee, so packing on a pound a year for about a decade increases your chances of developing arthritis by 50 per cent - a fairly powerful argument for running to keep off weight and protect your knees.

Of course, the decision doesn't have to be strictly utilitarian. As one of the Vienna study participants (who was preparing to run his 37th marathon) put it in a recent e-mail to lead author Wolfgang Krampla, "Even if minor aches and pains occur over the years, the gain in joie de vivre far outweighs them."

Alex Hutchinson is a former member of Canada's long-distance running team, and has a PhD in physics.


Go the extra mile

A long-term Austrian study of long-distance runners revealed that runners were less likely to develop osteoarthritis of the knee than non-runners were.

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