Yuri Elkaim, personal fitness coach, shows you a five-exercise Bosu Ball workout that will tone your abs fast. The first exercise is a pushup on the Bosu Ball with the spherical side down. With your torso down, lift one leg up from the floor. Bring the torso down, then back up, and pull the raised leg into your body, then back out. Alternate legs each time, and do as many of these as you can. In the second, turn the Bosu Ball flat-side down and align your buttocks and back on top of it so...