With apologies to those who have heard this story before (endlessly), I hope you don't mind me repeating it for the sake of the new runners. There have been lots of queries regarding the need for stretching and warming up and many different opinions. I can't claim to be an expert but these are my credentials such as they are; I have almost 15 years of running experience up to and including half marathons, I belonged to a club whose coach was considered to be one of the best running coaches in the country and I spent six months being treated by a sports physio.
So why have I only recently graduated from the C25K programme? Because two years ago my running was brought fairly abruptly to a halt when my lower back, glutes and right hip totally seized up. The muscles spasm was so great in my glute that it was pulling my right hip out of alignment and causing bursitis of the hip joint. The cause? Years of running and inadequate stretching. Just that. No other cause; no biomechanical problems, no 'wrong shoes', no accidents. Just years of gradual stiffness, that then causes an imbalance, when then has a knock on effect elsewhere... I may have got away with it up to a point if I had taken the time to do core strength and glute work but basically the cause was miles and miles of running without proper stretching.
I have heard it said again and again 'I don't stretch and I am not getting any problems'. How do you know? It isn't instant, it comes from a build up over time. If you are lucky (like me) and are a fairly neutral runner with no biomechanical problems, it may take years. If you do have problems, you may not know about it yet but believe me, you will find out much sooner. It only takes the slightest bit of imbalance that is imperceptibly magnified over time to become a major problem.
I lost two years of running, for six months there is no way I could even try and even once given the go ahead by my physio I kept trying and failing when the injury constantly flared up. Even now, I have to regularly miss runs when I have pushed too hard on either time or speed. I have to take walk breaks when I feel my hip stiffening up and may never again be able to run continuously for long distances. Or at least, my physio said it is possible but only if I can devote huge amounts of time to strength training and extra stretching - time I just don't have. But one thing is certain, never again will I say I don't have time to stretch after a run!