Take a look at Dr. Yessis’ article over at Running Times, “Are You Overstriding?” Here’s an excerpt:
Many long-distance runners believe that they are “overstriding,” the latest buzz word in running. A few years ago very few, if any, were ever concerned with this running “fault.” Runners tend to define the act of overstriding as any touchdown on the heel. Some coaches even state that overstriding occurs whenever touchdown occurs in front of the body. In this case, since all long-distance runners touchdown somewhat in front of the body, does this mean that all runners overstride? Can we legitimately call a heel or midfoot touchdown one to two feet in front of the body overstriding?