Stand with both feet together or spread a few inches apart (2-3"), but parallel with each other while holding a 1-2 lb soft sponge ball or weighted medicine ball. Depress and retract your scapulae (pull your shoulders down and back) while simultaneously engaging (contracting) your abdominal muscles to avoid any excessive arching in your low back. Bend your knees very slightly and keep your abductors and adductors under tension (contract your inner and outer thigh muscles). This will help avoid excessive hip adduction (sideways shift) during the single-leg stand. This exercise is best performed with a partner, but can be performed without one.
Starting Position: Slowly lift one leg 3-6 " off the floor, stabilizing your body on the stance (supporting) leg. Avoid any sideways tilting or swaying in your upper body and try not to move the stance (supporting) foot. Hold the ball close to your body, centered at chest height
Movement: To do this exercise you will need to establish targets in the space around your body. You can follow a partner's cues or select your own targets. Holding the ball, reach out and extend both arms to touch the targets you've established.
Your initial targets should be level with your chest and torso, or overhead, but positioned in front of your body so that it does not require any movement of your hips or torso.
Exercise Variation: As you master the starting positions, increase the intensity of the exercise by (1) reaching down towards low targets that require either a forward bend in your torso or single-leg squat, or both; and (2) reaching low or high, and around to targets positioned below your waistline or above your shoulders.