Have a question for a vascular specialist...Please answer!?

I recently went to a podiatrist to find out about a chronic problem I have had for...well, as long as I can remember...but just kind of put up with. Whenever I exercise (i.e.kickboxing, bikeriding, esp. rollerblading), the sides of the bottoms of my feet cramp up almost immediately. Wearing 'good' shoes makes it even worse, so I usually exercise barefoot, but with my newly developed heel spur, I'm not supposed to do that either. My podiatrist (who is also a surgeon) x-rayed my feet and said that the structure of my feet is normal and that the problem is a vascular issue. I've looked online everywhere online for information or for similar symptoms, but can't seem to find anything. Is there a vascular specialist who can shed some light on what is wrong with my feet? It never seems to improve or get better...has anyone ever dealt with this problem?