The lead P.T. Instructor taught my acadamy class to tuck our laces inside of our shoes. Weather we were wearing boots or shoes. The main reason was that he and a fellow officer were involved in a foot chase, the subject jumped a four foot chain link fence. His partner supported himself with one hand to clear the fence. As his one foot was coming over the top, a dangling lace caught the fence and the officer landed face down in the dirt. The subject was caught by another unit, luckily.