Sit straight up at the edge of your chair with your feet flat on the floor. With your arms at your sides, open up your chest, pull your shoulders down your back and pull your abs in and up from your belly button. Now, use your core to lift your right knee and extend the foot straight out from the knee. Hold 10 seconds. Now, bend the knee and slowly return the foot to the floor. Repeat on opposite side. Continue alternating until you’ve done 5 on each side.