What’s the deal with those big bouncy balls taking up space around the gym? Stability balls — also called exercise balls, balance balls, Swiss balls, or fitness balls — are more than just fun to sit and bounce on; they’re a great way to improve strength, cardio endurance, and balance. By tackling basic moves on an unstable surface, your muscles may get more bang for their buck. Use this workout to build strong legs and abs! ~ Berceste