Cross-training for runners.

A runner’s idea of cross training is usually more of the same. When they run, all their movements are in the sagittal plane (http://en.wikipedia.org/wiki/Sagittal_plane). So if the idea of cross training is riding a bike, it is more of the same type of movement. In the preparatory/conditioning phase of your plan, you should introduce lateral movement, like tennis. Or you can do circuit training that includes side lunges and lateral step ups. You will become a well rounded athlete and prevent over use injuries.