This is a compound exercise which works the chest.
1) With a dumbbell in each hand, lie on a flat-bench.
2) Start with your arms extended so the dumbbells are together up above your chest, with your palms facing forward.
3) Inhale as you lower the dumbbells by bending the elbows out to the sides (elbows should be at 90 degrees as they become level with the shoulders) until you feel a slight stretch in the chest or shoulders.
4) Exhales as you return the dumbbells back up to the starting position.
5) Repeat for repetitions.
Caution: When you are done, do no drop the dumbbells next to you as this is dangerous to your rotator cuff in your shoulders and others working around you. Just lift your legs from the floor bending at the knees, twist your wrists so that the palms of your hands are facing each other and place the dumbbells on top of your thighs. When both dumbbells are touching your thighs simultaneously push your upper torso up (while pressing the dumbbells on your thighs) and also perform a slight kick forward with your legs (keeping the dumbbells on top of the thighs). By doing this combined movement, momentum will help you get back to a sitting position with both dumbbells still on top of your thighs. At this moment you can place the dumbbells on the floor.