Starting Position: Stand with your feet feet hip-width apart, arms by your sides, depressing and retracting your scapulae (pull shoulders down and back) without arching your low back, and "brace" (engage your abdominal / core muscles) to stiffen your spine. Downward Phase: Begin your downward phase by first shifting your hips backwards then slowly moving downwards to create a hinge-like movement at your knees. Continue to lower yourself until your feel your heels about to lift off the floor. Try to maintain a flat back by bending forward at the hips, keep your head facing forward and position to your arms where comfortable or where they offer the greatest degree of balance support.
Jumping Movement: With ONLY a very brief pause at the bottom of your downward phase, explode upwards through your lower extremity, achieving triple extension (pushing and extending your ankles, knees and hips simultaneously). As you jump into the air, keep your feet level with each other and parallel with the floor.
Landing: The most important components of the landing phase are correct foot position and avoiding excessive forward movement in your lower extremity which places additional stresses upon your knees. Attempt to land softly and quietly on the mid-foot, rolling backwards quickly towards the heels. Always push your hips backwards and drop them downwards to absorb the impacting forces associated with jumping. Avoid locking out your knees or quads on your landing as this may lead to potential knee injuries.
Exercise Variation: Perform repeated jumps with no rest in between each repetition.