Place one leg on platform directly in front of you. Ensuring the safety bar is removed, exhale and press the platform away from you, engaging your quad as you do so. Press it all the way up until your leg is fully extended in front of you. Do not lock out your knee. Inhaling, slowly lower the platform until your upper and lower leg form a 90-degree angle. Pause for a count of one, and then repeat the movement. Once all reps on one side have been performed swap to the other leg.