Challenging the eccentric (negative) strength of a muscle makes it stronger, since the strongest fibers get the chance to work hard. The dragon flag is one of the most demanding bodyweight core exercises in the game for this exact reason. Using a flat or decline bench, secure the hands behind the head, and raise the entire body up as vertically as possible. There should be a straight line from shoulders to ankles. Allow your body to descend slowly, resisting a quick "drop" by bracing your abdominals. Keep your butt away from the bench for as long as possible; the body should touch the bench all at the same time — not in parts.