the outside front of my left forefoot callus is completely gone, about 2 square centimeters of it, torn off during a track meet. In 3 years of barefoot running it's the first time I've lost that much callus, now there's a big hole several millimeters deep with soft skin under it. And right in the exact place where I land first. Pretty damn painful too. Are there any clever methods of protecting that rookie skin, other than running on grass? Substances, tapes, adhesives, that kind of thing.