My lower back, like at the very bottom, an inch or two above my butt, gets extremely tight sometimes after workouts, to the point that it's a little uncomfortable. It doesn't even have to be back day, when I'm doing squats it'll tighten up and I have to sit down between sets. It's been like this for a while but has been bothering me a little more lately. The last couple months it'll feel a little sore multiple days of the week, even if I haven't lifted that day. When I arch my back and stick my stomach out I can feel the tightness I described, even as I'm sitting in my chair right now I can feel it.
It doesn't really effect anything, I can still deadlift and squat perfectly fine and it doesn't really hurt while doing excercises, it seems to get bad after I'm done. I guess the best way to describe it is: compare the feeling in my lower back to when you've just working something like your triceps and they're so pumped it's almost painfully uncomfortable.
Am I overthinking it and my back's simply sore from working out? I've tried taking a week off but it didn't really make a difference. I can't think what else it could be, if I had really injured my back I'm sure I would be in a ton of pain by now after hundreds of deadlift reps. I'm thinking about seeing a chiropractor when I'm home over Christmas, when I was younger I had back trouble and I had a doc 'straighten stuff out' and it got a little better.
As funny as it sounds, I sometimes also get this 'back tightness' after running for long distances. I remember during track in highscool at times I'd have to lay down because my lower back was so sore after running.