HOW: Get set up by hanging from a pull-up bar with your shoulder muscles and abdominal muscles engaged. From here, rotate your hips to the side and then tuck your knees up towards your chest. Return the legs to the starting position and then rotate your hips to the opposite side and again pull your knees up towards your chest.
FEEL: You should feel your abdominal and shoulder muscles working
COMPENSATION: Avoid arching through the back in this position. Keep your abdominal and shoulder muscles engaged.