A runner's worst nightmare (and indeed anyone looking to keep fit) is injury.  It is the one thing that stops you doing what you love and indeed can set you back quite significantly.  Like most runners I've picked up the odd injury here and there, and each time I've sought to understand what happened, and why?  I've learned we need to train the body holistically.  We need to look at the whole system not just the running component.  We need; a foundation of strength, to train the right energy systems in the right way at the right times, we need finely tuned movement skills, we need mobility and flexibility.