A variation on the standard barbell bent arm pullover, using only a single dumbbell.
Muscle group: Back
Lie on a flat bench with your head near or over the end of the bench. Hold the dumbbell above your chest by griping the plates of one side. Keep your elbows slightly bent.
Lower the dumbbell back behind your head, down towards the floor. You should feel the stretch in your chest and triceps. Continue until your arms are next to your head. Then reverse the exercise and return to the starting position.
Make sure you feel the stretch of the dumbbell bent arm pullover.