If i walk at a pace of 3 mph or higher, within 3 minutes, sharp pain begins radiating up the outside of my right leg, from my ankle to mid calf. why?

Varies: There are a number of possibilities, including a chronic exertion all compartment syndrome, tendinitis, even potentially a sciatica. An exam and appropriate studies can usually determine the cause. Don't hesitate to be seen.

Oh my Peronei.: It appears that 3 mph is the maximum speed that your peroneal muscles will function without straining. You description of location and symptoms fit the anatomy and function perfectly.