Starting position: Stand with feet hip-width apart. Engage your abdominal / core muscles ("bracing") to stiffen your torso and stabilize your spine. Pull your shoulder blades down and back toward your hips. Your arms are hanging comfortably along your side.
With the right foot planted on the ground, lift the left knee to hip height. Bend the elbows to ninety degrees. As you raise the left knee, swing the right arm forward and the left arm back.
Continue to brace the abdominals to keep the torso rigid and the spine straight. Lean forward on the right hip as you extend the left hip behind you. At the same time, reach the right arm forward and the left elbow back. Keep the right foot firmly planted into the ground to maintain balance and stability. To help maintain balance, find a spot on the floor and fix your gaze on that spot. This will create additional stability.
When you have reached what you feel is your end range-of-motion while balanced on your right leg, fully straighten the left elbow, keeping the arm at shoulder height. At the same time straighten the knee straight back to create full hip extension. Point the toes of the left foot toward the wall behind you in order to move into full extension of the left hip. Maintain abdominal bracing to ensure balance and stability. Try to keep the hips level. Do not let the left hip drop towards the floor or lift upward. Hold this position for 3-5 seconds.
Keep the abdominals engaged as you return to an upright, standing position. Repeat this movement for a specified number of repetitions or time frame.
Change sides and repeat for the same number of repetitions or period of time.
Exercise Variation: To add resistance and increase the level of difficulty, hold a dumbbell in your left hand (the weight should be in the hand opposite the standing (balance) leg).
If balancing on the right leg, use the left leg to help move into a position of flexion on the right hip; pointing the left leg backwards while pointing the toes and straightening the legs will help move the right hip into a position of flexion.