So, I wasn’t able to lift due to a (non-lifting related) lower back injury for 3 weeks; I ate at maintenance during that time. How am I supposed to start off again, like, how much should I deload and so on?
I’m 18, 6’4’', had been lifting for a month when I had my injury in case that’s important.
If your doc has cleared you, drop the weight back quite a bit on any exercises that involve the lower back and see how everything feels. I would err on the side of caution at least for the first week or two as you don’t want to aggravate or reinjure yourself. If you feel strong and don’t have unusual soreness or pain after lifting light for a week or two you can go back to where you were.
Since you’ve only been lifting a month it’s not like going light for a couple of weeks is going to majorly affect your progress. Overall you should be fine if you use good form and common sense. When I was younger I pushed through a few injuries failing to realize that many injuries can cause cumulative and reoccuring damage if not properly treated. I now have the surgical scar to prove it.