I mean to the point where, during my last two sets, I can barely go down all the way because my lower back is super tight. I don't mean "tight" like "inflexible," I just mean tight like it's all pumped. Think of after you do biceps and you have a huge pump if you tried to scratch your right shoulder with your right hand... you can't reach cuz you have a huge pump. Same feeling. It's weird. And since my gym is by my work, that means I have about an hour drive home after I work out, and sitting in my car for an hour with a crazy lower back pump sucks. I remember reading about this happening to some people before and I was like "whoa, that's weird," but I had never experienced it before. Now I have.