Barbell Row Back Angle
When performing the barbell row, it's important to pay attention to back angle. Not so much to prevent injury, but more so to focus on desired musculature. The closer our back is parallel to the ground, the more of a pure back exercise the the lift is -- we significantly engage your lats in this position. As we begin to stand up and our back approaches a more vertical angle, our traps and shoulders start to take over. In essence, the row goes from, well, a row, to more of a shrug or an upright row. Unfortunately, many times a lifter will lift his or her chest and become more upright because he or she is tired; or, other times, he or she will begin to stand up because the weight is too heavy, and by standing up, the lifter is less inclined to have a rounded back. If you find yourself in either scenario, you're too tired to execute a proper lift or the weight is too heavy to execute the right form, stop. Rest, or use a lighter weight, a weight more suitable for your strength level.
*Seen in the picture, from left to right, is a progression from more of a back exercise to that of a trap and shoulder exercise. A properly performed row needs to have a flat, neutral back parallel to the ground.