Mr Wooo is correct, either straight or bent arm pullovers with BB/DB's. Faust is also correct with regards to military presses. In fact any overhead pressing, either BB or DB, affects that region. Chins, BP's and even situps also. In fact most exercises will recuit these core stability muscles. But the more direct affect will be from pullovers, in any form. Overhead presses and chins second choices. Good Luck.
