Muscles in the leg and shoulders can be tight prior to running. Stretching can help to maintain flexible muscles for running and allows for muscles and joints to work more efficiently and decrease muscle stiffness. Dave Drennan, a leader in the Abe's Army, provides some basic stretching exercise in this video to help you run.
ON THE NET:
MAYOCLINIC: Slideshow: How to stretch your major muscle groups
Runner's World: Injury prevention -- Stretching
Wikipedia: Stretching entry
MAYOCLINIC: Stretching - focus on flexibility
Wellsphere: Warm-up vs. Stretching
