Recovering from injury and reps vs weight

About me broad, tall, 16 stone 3 pounds - mostly from fat thats all on my front and what leg leg muscle I have remaining, lightest I have ever been since being a little kid is 13 stone 10 pounds, that was two years ago. (I was 16.5 stone of mostly leg muscle at 14) My blood pressure is below average + cardiovascular system is above and I eat ~1600 calories a day.

My upper body strength is inadequate imo, I've never been into lifting or any of that, I am only good at carrying fridges, wardrobes etc - ironically joined a gym to improve this and was in surgery a week later. I cannot do anything that puts my weight on my wrist like a push-up or a dip or use any weight that will make my, weakened, wrist move because of strain. (so no heavy dumbells) Cause of the knees I can't use cross trainers, no idea why, and I am essentially on a time limit - so for example I can last about 3 minutes going full pelt on a rowing machine but only 4.5 at a leisurely pace before my knees are gone, so my cardio is high intensity bursts mostly and I'm really nervous about squats and dont know if I will be able to do them.

My routine for 2 months after recovering from surgery was: a few laps of a football field, 12, various, sets of 20 at 6-8kg with a dumbell for my shoulders, 5 to 8 500M sprints on the rower, 10 minutes medium cycling, 6 sets of 20 leg curls at 30kg - I could do 3 sets of 15 chinups at 52kg setting and an hour swimming. Did it 6 days a week and was at 16 stone at the time. I want to get back up to the cardio side and improve the power side.

FYI the knee injury left my barely able to walk for 18 months, joined a gym after getting back to moving then had surgery a week latter.

P.S cant swim anymore the pool was shut down.

/r/Fitness Thread