1. Begin in a plank position with your hands directly under your shoulders and shins place on the ball, forming a straight line from ankles to your head.
  2. Brace your core, and do not allow your lower back to arch. Keep your feet, pelvis, and shoulders in one line.
  3. Slowly take your left leg off the ball and lower it down and to the side to briefly touch the floor. Bring it back to the starting position (your shin on the ball) and repeat on the other side. Continue alternating sides for the prescribed number of repetitions.

Tip: Press down into the ball with your remaining leg and squeeze your glutes to stabilize yourself while your other leg is moving.