[Quo Fan]

I talked to my wife about this (exercise physiologist/athletic trainer) and she said to stretch your hamstrings. You would probably need to strengthen your quads, too, because both sets of muscles join in the relatively same place in your lower back.

I would seek out the opinion of an athletic trainer, because they know the mechanism of injury, how you get hurt. They will then suggest methods on how to prevent further injury, and methods on how to repair the current injury.