After a year of running in town, as opposed to when we lived on a acreage, my biggest nemesis is glass! I run on paved bike trails, and I've had to remove shards 3 times this summer. It's what you can't see that gets me! Tiny shards, and they hurt like ***k! Very hard to remove especially when embedded on tough skin. But, damn the torpedos, I'm not shoeing up! There, rant mode now off!