Grab a pair of dumbbells with an overhand grip and lie down on a flat bench. Extend arms out to sides so they are at chest level.
In a controlled motion, lower arms so that palms are facing each other and dumbbells are directly under your chest. Pause and squeeze chest muscles together at the bottom of the movement. Slowly raise the dumbbells in an arc up and away from your body. Once the dumbbells are almost in line with chest, reverse the movement back to the starting position.