Begin in the Tall Plank position with your hands aligned directly under your shoulders, fingertips pointed away from each other. The shoulders, hips, knees and ankles should all be in a straight line. As you initiate the descent, the elbows should travel backwards, with the upper arms staying as close to the body as possible.
Maintain full core tension for the entire time you are descending. Your body should travel downwards until your arms are at 90 degree angles, or until your chest touches the ground. If at any time you lose core tension and are unable to maintain the straight line through the shoulder, hip, and ankle line, you have gone too deep into the movement.