I've heard of people who get painful pumps when working back but I don't think what I'm experiencing are the same thing. Over the past few weeks whenever I begin training chest I immediately begin feeling a cramping sensation starting fairly low down on my back. Once I rack the weight and there is no tension is when the cramp travels thru out my entire back. When it is at its peak the pain is incredible and I can't draw a breath for about twenty seconds until it starts to ease up. It also gets going when doing any type of lat pulldown. Rowing movements don't seem to cause the cramps , not much anyway.