The New York Times Phys-Ed section discusses a recent Harvard study on running form.  The study examined injury rates among heel strikers vs forefoot strikers.  The subjects were 52 runners on the Harvard cross-country team.  Researchers looked at four years worth of data on injured runners.  The pertinent finding is this:

“About two-thirds of the group wound up hurt seriously enough each year to miss two or more training days. But the heel strikers were much more prone to injury, with a twofold greater risk than the forefoot strikers. (Emphasis is mine.)”

Be careful though.  This finding doesn’t necessarily mean that everyone should immediately change their running form.  The article quotes says:

“Does this mean that those of us who habitually heel-strike, as I do, should change our form? “If you’re not getting hurt,” Dr. Daniel Lieberman says, “then absolutely not. If it’s not broke, don’t fix it.”

But, says researcher Adam I. Daoud, who was himself an oft-injured heel-striker during his cross-country racing days, “if you have experienced injury after injury and you’re a heel-striker, it might be worth considering a change.”

For further discussion and analysis on these findings, have a look at Runblogger’s post (and how these findings are being misused in advertising) and the post at Sweat Science.  Both of these guys do a great job of telling us what the data does and does not show.