Start by lying on the mat with legs in tabletop position (90-degree angle) and weight in both hands overhead. Trying to use only your core muscles, slowly lower your heels to tap the mat as you lower the weight behind your head. Squeeze hands inward on the weight to flex the arms and return the weight overhead. Flex lower abs to lift legs back to the starting position. Make sure not to rock up and down, or to let your legs to take over the movement. If your abs aren't burning, you aren't doing it right!