Choku zuki, one of the first attacks taught in Karate, is a straight punch in the solar plexus. You should use your whole body as one while doing choku zuki. Many practitioners will only use the arms when punching, but incredible power is created when whole body is used. Start the right arm punch from the right leg. Prepare the punching arm by squeezing the right rib cage down a little bit. You can improve this by lowering the right shoulder. Obviously, this lowering is not shown when doing choku zuki correctly. Push through the right leg, then drive with the hip, next use the rib cage and shoulder then finally the arm. So you do the punch with the whole body, not just the arm. Push through the right leg, then move along with the hip, use your rib cage and shoulder then finally the arm. So you do the punch with the body and not the arm.