While standing with a shoulder width stance, take a medicine ball and hold it at chest level. Starting with the hips squat down and back looking up and holding your low back tight until your hips become parallel to the floor. Don't let your knees come out too far out in front of you as it will take the stress off the bigger muscles of the upper leg (the glutes and hamstrings) Explode back up to the starting position and then repeat. High reps should be used for this exercise because it will be hard for you to hold a heavy enough medicine ball to get maximal strength benefits from doing this. This is best suited for conditioning and recovery purposes.