In fact, way back in the old days before the invention of bench presses with upright racks for holding the bar, guys would do a barbell pullover, lifting the bar from the floor to their chest, and then do their bench presses. But gradually over the years this exercise got pushed to the wayside and is hardly ever done by the average gym goer.
The main benefit from pullovers is that they help expand the rib cage and work all the supporting muscle groups along the torso, chest, lats, arms, and shoulders through a full range of motion. This can really help add thickness and depth to your torso, which is one area that a lot of people lack these days.
I know from the majority of people that I see at the gym that very few of them have a well developed torso. It's actually quite common to see a guy with muscular arms and shoulders stacked on a slim chest and torso. But by adding pullovers to your routine you can help fill out and expand your rib cage and correct this problem.
Your rib cage is the frame work that supports all your upper body muscles. So if you have a well built frame underneath, the muscles of your chest, shoulders, lats, and arms will look much more impressive.
I was fortunate enough to have included pullovers as a regular exercise in my workouts from the start and I think this has certainly helped me to develop a large rib cage and good chest expansion, which is clearly seen when I hit a side chest pose as in the pic above.
The main reason I even did this exercise was the fact I started training in a simple home gym and didn't have access to a lot of the fancy machines that are so common in most gyms today. So from having limited equipment I tried to include as much training variety as I could using basic free weight barbell and dumbbell exercises. For this reason I sometimes feel that training with limited gym equipment can be a blessing in disguise.
There are two basic variations to the pullover, the barbell version and the cross bench dumbbell version. One is not necessarily better then the other, both work well. I personally feel that the dumbbell pullover stretches the chest a bit more and the barbell pullover places a little more emphasis on the lats. But you can pick the one that feels the best for you, or if you have no preference you can alternate back and forth between both variations. The main thing is that you just do them.
The pullover is a stretching exercise, so you'll make better gains from using a moderate weight, higher reps, and really working through a full range of motion. Add weight to the exercise in a gradual progressive fashion, but never at the expense of sacrificing your exercise form.
Depending on your body structure and how you do the exercise you may feel it working the chest, or you may feel it working the lats, or a combination of the two. So you could include pullovers with your chest or back workouts. The main thing is that you do them consistently so you reap the results that they have to offer.
The first time you do the exercise start off with a light weight and just get used to the movement and the range of motion required. Then go up by 5 - 10 pound jumps in weight each set. By going through this process you'll naturally find the sweet spot where you have enough weight that allows you to stimulate the muscles hard, yet still be able to perform the exercise through a deep range of motion and fully stretch out your entire rib cage, chest, and lats.
Start off with 1 - 2 warm up sets and then take a working weight that allows for 15 reps with good form. Do 2 - 3 working sets and really focus on feeling the muscles stretch and contract with each rep. Another little tip that will help add to the effectiveness is to take a deep breath before each rep and hold your air in as you lower the weight. This will give you an even deeper stretch throughout the rib cage.
You'll get more benefit from doing pullovers at the end of your workout when your muscles are already pumped. Doing stretching exercises when you are pumped up and the muscles feel tight will aid in muscle growth because the connective tissues are already being stretched from the blood volume in the muscles, and then by doing stretching exercises at this time as well you get a double whammy effect. This really stretches the connective tissue and increases your muscle growth potential.
By doing pullovers as a staple exercise in your workout routine you are going to experience a good upper body growth spurt and also notice an improvement in your flexibility and mobility for a lot of your other exercises as well. Give it a try and don't be surprised if you add an inch or two to your chest measurement in as little as 6 weeks.