This exercise is used to build strength and size in the chest. The triceps and shoulders are also used during this exercise. This is a variation of decline barbell bench press; when using dumbbells, stabilizer muscles are worked harder. Your body has to work harder to keep the dumbbells in place and along the correct path.
Begin by securing your feet into a decline bench, which can be found in almost any gym. You should have the dumbbells resting on your thighs. Now lay back onto the bench press, the dumbbells will move with you and be at shoulder height. You need to rotate your wrists so that your palms are facing away from you. Next, push the dumbbells with your chest muscles until your arms at locked out above your chest. To complete the movement bring the dumbbells back to the starting position. Repeat this movement for a number of reps, then carefully get up off the bench.
It can be easier to have a spotter hand you the dumbbells. To do this, lay back on the bench and then have your spotter place the dumbbells on your chest.