Now that I run in the park I've been making a joyful acquaintance with gravel. Since I try to follow Laura's c25k+ advice to kick up your heels and get a circular leg motion going, Ialso kick up gravel and every run some of it flies up, lands on the back of my trainers and makes its slow, pointy way down my heel. I have to decide whether to stop and dig it out or push my toes to the front of my trainers and let it fall inside, work its way to under my arch. I usually do the latter since I can't be bothered stopping but have quite a gravel collection in my shoes sometimes. Give me mud any day!