Should I rotate the running shoes I use?

You've probably been told that running in two or more pairs of shoes throughout the week can lower your risk of injury. According to a first-of-its-kind study, you've probably been told correctly, as runners who rotated among multiple models during the 22-week study had a 39% lower risk of running injury than those who almost always ran in the same shoes.

A:"I encourage everybody to have two pairs of shoes," says Jon Clemens, former track and field and cross-country coach at Columbia University. The reason? Compression. "Even with new advancements in running shoe technology like different types of EVA foam, shoes have memory, and they get compressed," Clemens says.

More than a few people are guilty of training in the same ratty old pair of running shoes for months, logging hundreds or possibly, even thousands of miles on them before finally heading over to the local running shoe store to get a replacement.