Starting Position: Stand with your feet hip width apart, with the right foot slightly forward (the heel of the right foot should be parallel to the toes of the left foot), your body weight should be over the right foot, only the toes of the left foot should be touching the floor to help with balance and stabilization during the entire range-of-motion of the exercise. Gently contract your abdominal / core muscles ("bracing") to stiffen your torso and stabilize your spine, and depress and retract your scapulae (pull your shoulders down and back) without arching your low back and maintain this shoulder position throughout the exercise.
Downward Movement: Inhale and press the right foot into the ground so your weight is balanced between the ball, heel and outside edge of the foot (keep the toes of the left foot on the floor for support during the entire range-of-motion of the exercise). Slowly begin to bend forward at the hips while maintaining the abdominal bracing to avoid shifting or rotation of your torso. Maintain a flat back and head alignment with your spine (or head extended slightly upwards).
Maintain a tall spine with the abdominals braced, push your weight back into your right hip while allowing the right knee to hinge, you can either hold your arms by your side (as pictured) or hold them out front as a counter-balance. As you are lowering yourself, maintain your weight through the ball of the foot and heel of the stance (supporting) foot, keep the pelvis level and the hips aligned during the full range-of-motion of the exercise.
Upward Movement: keep your bodyweight in your right leg and foot, exhale and slowly push the right foot into the ground to start moving upwards (by extending your hip and knee) to return to the initial standing position, maintain the core bracing through the entire movement to help keep the hips level and control balance.
Switch the stance (supporting) leg, and complete another set of repetitions on the other leg.
Exercise Variation: As this technique is mastered, the exercise intensity can be progressed by (1) lifting the supporting leg off of the floor. This increases the need for balance and stabilization within the body; (2) adding external resistance by holding a dumbbell in one hand or a medicine ball in both hands; (3) bending over and / or lower the hips closer to the ground increasing your knee bend; and (4) standing on unstable surfaces (e.g., Airex pad).