Hi, for some reason I'm very very weak on inverted rows. However, I'm very strong on chin ups. I can easily do 12 reps of chin ups (no cheating, all the way down, no using momentum or kipping) and can do reps of chin ups with 30+ lbs on me (I'm 170, 5' 9"). When I do inverted rows, I can't touch the bar to my chest or sternum, no matter how hard I try. I'm about two inches off. If I use momentum and pull hard I can sometimes touch it, but I can't otherwise. Why is this? What part of my back is so weak, and what exercises can I add to fix it?