There are countless exercises performed throughout the ages, and even more variations made, that people will tell you gives you the thickest and widest back imaginable. We all crave that back like Arnold had. Arnold had the total package, thickness, width and density.
Just as there is more than one workout program that will get you stronger, there are also more than 4 exercises to get you a bigger, stronger and wider back. These are just 4 that I believe are staples and that have worked well for me over the years.
1.) Dumbbell Row
The dumbbell row, when performed correctly, can be one of your best upper body movements to add on some serious thickness and attack your lats/rhomboids like none other. It is important to not go heavier than your body can lift. There are cheater rows and you can get big off them but an exercise done correctly is ten times better than an exercise done poorly with more weight. To perform the dumbbell row you will need one dumbbell and something to brace your body with: I will use a bench.
Place the dumbbell on the right side of the bench. Placing your left leg on the end of the bench, bending your torso over at the waist until your about parallel to the bench, keeping a tight core and neutral head spine. Place your left hand on the bench for support and your other arm to pick the dumbbell off of the floor with, this is your starting position. From here you will retract (pull) your arm upwards and slightly back resembling the action of starting a lawn mower. Keep your elbow tight against your body, remain core tight stabilizing the spine and squeeze your back as you row the dumbbell up. There should be no rounding in the back or excessive extension, it should be flat as if you are performing a plank. You should feel the movement throughout your entire upper back, lats especially. If you feel it more so in your arms, forearms or shoulders then lower the weight and check your form.
2.) Dumbbell Pullover
The dumbbell pullover is more of an old school exercise but is slowly making its way back into existence. This movement elongates and stretches the Latissimus Dorsi muscles and opens up the rib cage. Not only is this a great way to target your lats and build a wide back but it is also used as a chest developer on the concentric portion of the lift. I will show you the simpler way to perform these lying my back flat on the bench as if I was performing a flat bench press. The range of motion is just about the same this way as if you were to perform it lying perpendicular using a hip drop to counterbalance the weight.
Grab yourself a dumbbell holding it as you would for a tricep extension, palms in contact with the barrel of the dumbbell and the handle positioned in between your thumbs and pointer fingers. To start, hold the dumbbell above your chest (sternum) with straight arms. Begin to slowly lower your arms holding the weight behind your head, arms slightly bent taking them as low as your shoulders will allow. As you bring your arms back behind your head feel the muscles stretch and get long. Once you have gone as far back as your comfortable can reverse the movement and bring your arms up back overhead into the starting position over the chest. If the movement causes too much strain or discomfort on your shoulders, lower the weight or refrain from this movement completely.
The deadlift is commonly known as a total body exercise taxing especially the posterior chain so, of course, it's essential to building a thicker back. Deadlifts stress every major muscle group in the posterior chain, from the base of the erectors all the way to the top of the trapezius. To build a strong back with the deadlift it is best suited to train them with lower rep ranges and volume but with maximum effort and heavy weights!
To set up the deadlift (conventional) you will have a loaded barbell placed in front of you. Walk up to the barbell placing your feet slightly inside of shoulder width apart with your toes pointed out slightly. For the basic gym goer, position the barbell roughly an inch away from your shins and over the midline of your foot (It is beneficial to wear flat shoes when performing this lift, or go shoeless). With your arms straight down by your sides begin to push your butt back and bending your knees until your fingers are in contact with the barbell. Once you can grab ahold of the barbell firmly, do not go any lower. From here you will sit back into position, keeping your shoulders higher than your hips and your chest up. Next you will want to engage your lats by turning your elbows inward (This is more-so for the advanced lifter). Maintain a neutral spine, staying core tight and begin to pull the slack out of the barbell (you will hear a clicking sound).
You are now ready to lift the weight off of the floor. Begin by driving your hips into the barbell, twisting your feet into the floor, recruiting as much muscle to complete the lift. Keeping your shoulders behind the barbell, chest upright and arms straight the entire portion of the lift. Once you have completed the lift, reverse the movement by pushing your butt back as if you were trying to hit the wall behind you and lower the weight in a controlled manner. This lift is very dangerous if done without proper training, but the benefits when done correctly are fantastic.
Plain and simple, the basics work. In my opinion there is no better exercise for back width than using your own bodyweight for pull-ups. There are many variations to the pull-up regarding hand placement. I personally am a fan of the overhand grip, slightly wider than shoulder width apart, like so in a lat pulldown. There isn't much science to it, you simply hold the pull-up bar and pull yourself up. Stay core tight while performing these and imagine as if you are pulling that bar apart as you go up to really target those outer lats (This is with the overhand grip as stated above). As with any lift, don't rush through them too much. Try to get some good time under tension and let the muscles work. Working pull-ups in high rep ranges seem to work well for me. I like to do 50 or 100 pull-ups and see how few of sets it takes me to complete. If you can complete 50 reps in 2-3 sets or 100 reps in 4-5 begin to add weight when performing your pull-ups.