The dragon flag is an advanced bodyweight core exercise that can help build great overall core strength and incredibly strong, defined, six-pack abs (also known as dragon flag abs). It is credited to martial arts master Bruce Lee and is one of the more advanced ones he used in his physical training. Because it is not only difficult but places a lot of strain on your joints, it should only be attempted by more advanced exercisers and athletes with a high level of overall body strength.
Get into proper position by locking your arms in a fixed overhead position. You can do this on a bench, with your hand next to your head and gripping the sides of the bench, or you can grip a stable object overhead. Some people use kettlebells or a barbell, but using something fixed and stable is a bit more practical, and quite a bit safer.
Contract your torso and drive your legs up as if you are performing a reverse crunch, but keep your body rigid from your shoulders to toes, and avoid bending the hips. Point your toes to help maintain proper body alignment.
Once lifted, slowly lower your legs in a controlled motion without letting any part of your body touch the bench other than the upper back and shoulder. If you cave in, drop your hips, or arch your back, you don't have the strength yet and you should not continue the exercise.
Lower your body until it is hovering just over the bench.
Repeat as possible. Once you break form, you are done.