The serratus anterior stabilizes the scapula (shoulder blades) for motions of external rotation – such as the back swing in tennis – and upward rotation – like the tennis serve.Serratus Punch:Assume a position on your back – with arms extended and hands at front shoulder level. With or without a light dumbbell or filled small water in each hand, perform a punch -up towards ceiling while maintaining elbow extension. Return to the position of your back against the ground or table. Try 5-10.