Set Up: Place both of your forearms on a stability ball with your legs extended behind you. Tighten your abs and lift your hips. Make sure you are balanced and stable on top of the ball [A].
Action: Hold your position as you lift one leg off the ground several inches; avoid arching your lower back [B]. Hold for two breaths, and then return to the starting position. Repeat, alternating sides.
Make this move easier: Perform this move on a mat, without the ball.
Make this move harder: Pulse your leg 10 times in the lifted position.