Two weeks ago I sprained my ankle running- I guess it was just from over use because I did not trip or twist it or anything like that, but the doctor verifies it is a sprain. I have worn an ankle boot for thw two weeks, and done some mild exercises that the doctor gave me. I do not have access to an exercise bike or swimming pool, so I have been unable to do any real cardio on this down time and I am so anxious to get back into it. My ankle is still pretty sore. When can I start running again? Im afraid if I wait until it stops hurting I am going to lose a lot of valuable time (Im training for a 1/2 marathon).