I am new to running and dont go for a terrribly long runs. Today while running on a treadmill that I have used befor and after stretching I ran for about 4K whne my right toes and then eventually the whole left foot went numb. This has never hapend before and I am hoping that this is just a problem of shoes tied too tightly. Fortunately this occurred near the end of my planned run but I would have had to stop had I been trying to go further. Just left foot, no pain in foot or calf just pins and needles in left foot as if it had gone to "sleep" so to speak. This thread has been very helpful and I will try some of the suggestions listed here. After I broke from the run to a fast walk and cooled down the numbness went away. Thought it might be a circulation problem but the nail beds on the toes look fine and no problems at all now. Weird and scary but I will see if it occurs again and try various suggestions listed here to see if they remedy the issue.