Top of my left foot hurts as I run?

Hi. I am a podiatrist. The pain you describe is your long extensor muscles (extensor digitorum brevi). These muscles are small anti-pronator muscles. The big anti-pronators (anti-rolling in) get tired, then they recruit the little ones to help. But, they are small and get tired even more quickly. It's like a war, after the infantry get shot - you send in the cooks armed with a gun but they don't last very long. See my website at www.walkwithoutpain.com.au for some info sheets on this topic. See a podiatrist. You need orthotics (for sure).. I charge 580 Australian dollars so be prepared for that sort of expense.