Have a single dumbbell in your hands. Start with your back against a wall with your feet shoulder width apart. Engage your abdominal muscles and slowly slide your back down the wall until your thighs are parallel to the ground. Adjust your feet so your knees are directly above your ankles (rather than over your toes). Keep your back flat against the wall. Now bring the arms to shoulder level, extended in front of you with your elbows soft. Press the dumbbell to your chest and then extend the arms back. That’s one rep.