Place your legs on the platform directly in front of you, with your feet close together. Ensuring the safety bar is removed, exhale and press the platform away from you, engaging your quads as you do so. Press it all the way up until your legs are fully extended in front of you. Do not lock out your knees. Inhaling, slowly lower the platform until your upper and lower legs form a 90-degree angle. Pause for a count of one, and then repeat the movement.