People who lace up their running shoes and pound the pavement have a roughly 50% chance of sustaining an injury that interrupts their training. Among marathon runners, studies have placed the injury incidence rate significantly higher, in some cases as high as 90%.

It isn't running itself that's doing the damage, a growing number of physicians, physical therapists and exercise scientists say. It's the way people run. Too many runners stride too far out in front of their bodies, or land with their legs at awkward angles.

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