For the last few months I've been making an effort to walk and run totally barefoot more often. The first few times were difficult in general, but I got relatively used to it and can go a mile or more without any serious irritation now. However, one recurring problem I have is irritation (once blisters, now calluses) along the outside back of my heels, along where it comes in contact with the ground. After running, the area is usually sore.
Does anyone have ideas as to what might cause this? I don't notice that the area gets rubbed much while running, at least not more than anywhere else. I've tried moving my legs slightly outward - it doesn't seem to help.