How to Perform the Barbell Row, or Bent Over Row
This movement is a horizontal pulling exercise commonly placed on back days (if following a traditional bodybuilding split) or pull days (if following a push/pull/legs split). This free-weight barbell exercise works the entire back, and more.
It primarily hits the latissiumus dorsi, middle and lower trapezius, middle back (rhomboids), posterior/rear deltoids, biceps (brachialis), forearms (brachioradialis), rotator cuff (infraspinatus, teres major and minor), and pectoralis major sternal head.  Yes, you read that right - barbell rows can contribute to chest development. The barbell row is performed standing, with a forward-leaning torso, so the following muscles are involved to stabilize the movement - biceps (brachii), triceps (long head), erector spinae, hamstrings, gluteus maximus, adductors (magnus), and abdominals (rectus abdominis, obliques). 
The barbell row involves muscles from knee-to-neck. No wonder it's considered the king of back exercises.
MTS Nutrition CEO Marc Lobliner shows you how to perform the king of all back exercises: the barbell row.
How to Perform the Barbell RowBegin by placing a barbell on the floor, selecting the appropriate working weight, and adding an even amount of weight to both sides of the bar. don't place 55lbs on one side and 35lbs on the other side of the barbell; doing so won't improve your gains and will likely lead to an injury.
If this is your first time performing the exercise then pick a conservative weight that you can safely lift for 8 to 12 repetitions. it's completely acceptable to start with only the barbell itself. In short, the barbell row motion is like a reverse flat bench press.
Once you've selected the appropriate working weight, approach the bar with a stance somewhere in between hip and shoulder-width. Your toes should be pointing forward or slightly outwards.
Once you've set your stance, grasp the bar with a pronated grip (palms facing away from you) at or slightly wider than shoulder width. An excessively wide grip decreases the range of motion and shifts the emphasis on the upper back rather than the entire back.
To begin the set pick up the barbell in a deadlift-like motion; you should be standing upright and bar should be about mid-thigh. While keeping your feet planted rigid, lean your torso forward to roughly a 45degreee angle; some knee bend is acceptable. Too much forward lean can place excessive torque on your lower back.
Some people prefer to lean so their back is parallel with the ground; this style of row is known as the Pendlay row. The Pendlay row is performed explosively, with the bar touching the ground after every rep. With this version of the barbell row the bar will not touch the ground after every rep; this keeps tension on the lats and forces an isometric contraction of the back to stabilize the torso.
Now that your torso is leaning at a 45 degree angle and your arms are fully extended (but not hyperextended), initiate the pull by flexing the lats and pulling your elbows back. Use your arms as levers for transferring power from your lats to the bar.
As you begin pulling your shoulder blades should start retracting the bar will move closer to your body. Pull the weight towards your upper abdominals, or halfway between your belly button and lower chest.
The bar doesn't have to touch your body for a rep to count; instead, focus on ensuring the proper muscles are working and pull the bar to the point that your shoulders and back muscles allow you. This is not an excuse to limit your range of motion or use excessive body English (swaying, jerks, swinging, etc...) to complete the rep.
Once you get a nice contraction in the back at the top of the rep, slower lower the bar back to its starting position with your arms fully extended. After you've completed the number of desired repetitions place the bar on the floor and rest until the next step. As you increase the weight on barbell rows you may be tempted to use more body English but strive to keep the form as strict as possible.
This exercise can be performed using straight sets, drop sets, rest-pause sets, supersets, trisets, giant sets, paused reps, partial reps, forced reps, or slow negatives. As with any exercise, the two most important components are high-quality form and progression. Progression can take a variety of forms (e.g. more weight, sets, or reps, decreased rest period, improved rep quality, etc...) but strive to improve every time you walk in to the gym.
Barbell Row Form Tips
Strap Up - If your grip gives out before your back and biceps then don't be afraid to use straps. Barbell rows are a back and bicep-building rather than a grip-building exercise.
The focus of this exercise should be to work the lats, upper back, and appropriate supporting muscles. A popular strap option is Versa Gripps.
Go Thumbless - Some people find they're able to improve lat and overall back engagement, decrease arm involvement, and pull more weight using a thumbless grip. Wrap your thumb over the top of the bar, alongside the rest of your fingers, instead of underneath the bar.
Avoid Momentum - Control the pulling and lowering of the bar during each repetition. don't allow momentum to make the movement easier unless you're performing an advanced technique like forced reps. Avoid rocking back during the pulling portion of the exercise otherwise,e the emphasis will move off the lats and on to the lower back.
As you become more advanced and proficient in your technique, feel free to initiate with an explosive pull to the torso followed by a slow lowering of the bar. Regardless of which repetition tempo you choose, you should remain in-control of the weight at all times.
Keep the Lower Back Neutral - With the 45 degrees forward lean of the torso, your lower back will isometrically contract to maintain total body stability. it's extremely important to keep your lower back neutral; don't excessively arch it or allow it to round.
Doing so drastically increases the likelihood of injury. One cue I recommend is to brace your abdominals for impact, as if you're about to get punched. This tensing of the midsection will ensure your lower back doesn't end up in an unnatural or dangerous position.
Vary the Grip - We discussed Pendlay Rows earlier in the write-up, which involves a more horizontal back angle and explosive pulling for each rep. Experiment with an underhand grip, neutral grip (if you have access to a football bar), and a wide overhand grip.
Each of these grips will still hit the overall back but the underhand grip emphasizes the lower lats and biceps, the neutral grip emphasizes the mid back, and the wide overhand grip emphasizes the upper back.