The Lighter Side of Preventing Overuse Injuries in Runners
"Pain free." These two words sum up a desire of every runner. And thanks to a steady flow of helpful research, runners are better able to stay one step ahead of potential injury. Two new discoveries have recently been added to this growing body of knowledge. First, it has been found that runners who land with higher impact have a greater tendency toward overuse injuries. Second, runners are at risk if the foot isn't correctly positioned to cushion the impact when it hits the ground. This can happen when the foot stays arched while in contact with the ground.

Normally, the foot will keep its arch until the moment the heel hits the ground. Then the arch lowers as the sole of the foot makes contact with the ground. This motion is called pronation, which is needed to help the foot absorb shock during impact. After pronation, the foot immediately starts to arch again as a way to power the next stride. If the foot doesn't start to pronate as the heel hits the ground, the foot remains rigid, putting the runner at higher risk for overuse injury. 

The authors used a special platform to measure the forces and foot positions of two groups of runners. The first group had past problems with one or more overuse injuries. The other group had no history of injuries. Measurements were recorded while each person ran on the platform. People in the injury group showed higher forces on impact. Also, their feet were sluggish when moving from the arched to the pronated position. As a result, the authors recommend that injured runners slow their stride during training as a way to lessen the impact.

The authors recognized that training habits can also be a source of overuse injuries. But modifying training routines are only one way--and often an oversimplified way--to address the problems of overuse. The authors are convinced that foot alignment and the way the foot works mechanically while running are what determine safe training levels. They also hope that future research along these lines will offer other new and helpful ways to prevent overuse injuries before they happen.
Alan Hreljac, et al. Evaluation of Lower Extremity Overuse Injury Ptential in Runners. In Medicine & Science in Sports & Exercise. September 2000. Vol. 32. No. 9. Pp. 1635-1641.