Branch by Per Bernal.
"I've done barbell rows with 500 pounds for 8 reps a few times. I tell you though, the toughest thing I've ever done for back is the 3 sets of 20 with 315 I do at the end of my workouts now. My lower back gets so pumped and tight, and the oxygen debt on that third set is unreal - you are literally sucking air trying to get a breath."
