Warmups are crucial to performance as well as injury prevention. Your muscle fibers have a similar makeup as celery. Trying to start a run without a proper warmup is like taking a piece of celery out of the freezer and trying to bend it. It snaps! Your muscles react the same way, if you run on cold muscles you increase the likelihood that you will injure yourself. If you allow a piece of celery to warm up it becomes more flexible and less resistant to change. So don't run on frozen celery and spend more time working towards your goals and less time injured.