When reading about girding our waist with the belt of truth, we learned from the Apostle Peter that this meant we were to gird the loins of our mind and that the belt of truth had nothing to do with our physical waist at all. Likewise, our feet are to be shod (covered) with the preparation of the gospel of peace. This piece of armor, that covers our feet, "the preparation of the gospel of peace", also has nothing to do with our feet.