Hang from a bar using a wide grip and pull yourself halfway up, elbows bent.
Keeping that elbow angle, push your chest forward in front of the bar, then pull it back behind the bar, moving at the shoulders.
Keep your head under the bar the whole time and repeat back and forth.
Risks
This exercise, especially when pushing your body forward, puts the shoulder in a potentially unstable position. Make sure you can perform at least 10 Pullup before attempting this exercise and progress with caution.
