Start by lying on your back on a yoga mat with your arms extended above your head. Engage your abdominal muscles by drawing your belly button in toward your spine and slightly elevating your legs off the mat. This is your starting position.
On an inhale, bend your knees and, using your abdominal muscles, draw them in toward your chest. Be sure to keep your feet together. At the same time, bring your arms forward toward your feet as you slowly lift your head, shoulder blades, and torso off the mat.
On an exhale, slowly lower your arms and extend your legs to return to the starting position without touching your feet down on the floor. This counts as one rep.