When you want to give your legs some extra attention, using a kickboard is one killer way to go. Using a kickboard while swimming either chest-down or chest-up is one way to develop strong leg muscles by isolating the glutes, hamstrings and quads, as well as other minor muscles of the legs. Incorporate kickboard exercises into your fitness routine several times a week, making sure to take at least 24 hours off between these workouts to give your leg muscles time to recuperate.