Bulgarian Split Squat without Weight

Stand a couple of feet from a park bench, with your back to the seat. Bend your right leg and place the top of your right foot on the bench as you place your hands behind your head. This is the starting position. Keeping your torso upright, bend your left leg and lower your body until your left leg is bent at least 90 degrees. Push your body back to the starting position. That is 1 rep. Do 20 reps, and then switch legs and repeat.