Pinterest is the go-to source of inspiration for almost everything these days--DIY projects, recipes, outfits, non-existent future weddings. It's no surprise pins also have the power to kick us into shape by banishing the usual excuses (I don't have time! I can't afford a trainer! I need variety!) We tried out the top four most re-pinned workouts on Pinterest to find which one deserves a coveted spot on your fitness board -- and in your exercise routine.