How do you do your BB rows?
That would ultimately depend on which part of your back you wish to target. Granted one can not super isolate one particular muscle amongst a group of muscles, however one should be able to throw more focus on one particular muscle and less focus on another by challenging it through body-positioning and barbell or dumbbell movement/path of travel. I'll give an example below to clarify what I'm talking about here.
Most often you see people in the gym (when I used to go to a gym), pulling the bar to their chest (for example), but when you ask them what muscle of their back are they really targeting, they answer you, "the lats of course mate, I want me some wings ya know!" well that will definitely happen, but it will take much longer to achieve since the muscles that are challenged here are the upper back muscles such as the teres major, rhomboids, infraspinatus, rear delts, mid-traps, and of course to a lesser degree the giant latissimus dorsi muscle amongst few others. Great if your aim was to challenge your upper back muscles, the ones that pop up when one does a double back biceps pose....and not the lat spread pose.
Another mistake I used to see when I used to go the gym was guys (who I knew could not lift big weights), lifting more than I was! Anyone can do it with bit of momentum mixed with bit of gravity defying magic. I'll explain.
You see the lifter with a 50kg d/bell positioned beside his waistline...now where do you think gravity would pull this 50kg dumbbell towards? If you said straight down toward the floor, you get no prizes sorry, because that's exactly how gravity works. But that's
not what you see this lifters do. They let that d/bell
swing out in front and away from their upper torso, and then pull it back in as if they were in some tug of war contest. Once that bar travels forward, you have shifted the stress from the lats to the front deltoids (and with 50kg, you're knocking on injuries doors)...all in the name of lifting "big bro"!
For maximum lats engagement, I keep the bar in constant contact with my thighs (as there really is
no need for it to leave that position and go away from my body)...unless I wish to get a lower back injury that is....then I pull it towards my waist line rather than my sternum or lower chest muscles...in order to maximally isolate the lats, in addition to affording them maximum pulling power. At a 45 degree angle is all I need to get the job done...higher than that and the focus would start to shift towards my mid to upper trapezius muscles.
Forgot to mention...there is a great way if you feel the need to stretch out the lats whilst doing some rows (as our friends with their 50kg dumbbell above were aiming to do) and that way is achieved through not a barbell..., not a d/bell, but a cable. A cable has its gravity (pull) shifted from straight down toward the floor, to a place where this cable originates....usually in front of you rather than below you. Thanks for your time.