Lie flat along a bench with your head near one end and only your upper back and shoulders on the pad, hips low, feet planted on the floor for a stable base. Hold one dumbbell vertically with both hands cupped under the top plate, arms extended straight above your chest. Keeping a slight bend in your elbows that stays constant through the rep, lower the dumbbell back and down in an arc until you feel a stretch across your chest and the sides of your ribs. Bring it back over your chest along that same arc, leading with your upper arms rather than muscling it up with your wrists.