I started having back issues during covid probably because I didn't have a proper place to work. I now lift or do some cardio for 10 minutes a day 4-5 days a we

I started having back issues during covid probably because I didn't have a proper place to work. I now lift or do some cardio for 10 minutes a day 4-5 days a week and have seen pretty drastic improvements. Much more than I thought I would experience given that 10 minutes feels like nothing and is the opposite of what I've been told by my more fit friends. I just bought a cheapish weight set and haven't gone above 15lbs on each dumbbell but my arms and shoulders have gotten noticeably bigger and my legs slimmed down quite a bit. Of course my back is much better and my posture as well. I was not big to begin with 5'11" 170lbs and I am not into fitness. I really don't enjoy doing it but 10 minutes usually will fly by and I can get on with doing things I enjoy more.