At the peak of my bodybuilding career, my chest measured 57", and one of the prime movements that made that sort of dimension possible was the dumbbell pullover. Some authorities disagree, but I firmly believe that doing pullovers for a number of years increased the size of my rib cage and kicked me toward that 57" mark. I further believe that the younger you are when you start training, the more effective this exercise is. For a teenager, I would recommend it as an absolute must for expanding the rib cage.
It also, of course, works the pecs, particularly the outer and lower areas, and it gives the lats and serratus a bit of a workout. So what are you waiting for? Roll that dumbbell to the bench and begin a set of pullovers.
Lie across a bench with your shoulders resting on the bench top and your feet flat on the floor. Grab a dumbbell and hoist it to arms’ length above your head, with both hands pressed against the underside of the inside plate. Then, with just a slight bend to the elbows and keeping the arms rigid, lower the dumbbell slowly behind your head toward the floor. As you lower the dumbbell, try to drop your hips a little toward the floor to increase the stretch. Once you have lowered the dumbbell as far as possible and achieved maximum stretch, return through the same arc to the starting position (dumbbell straight above the chest) to commence the next rep.
The accompanying chart shows a chest-specific, intermediate-level training routine incorporating pullovers. Follow this program twice a week, train hard and consistently, and the results will come. - FLEX