It does get easier really quickly, I started playing footie again in the gym with some mates, I was proper boloxed the first week, next week I was 10 times better, my knees and bones in general are knackered as well.
The job I do keeps me active but I still need cardio stuff as well.
Still can't get my body to do the stuff my brain wants to
btw, I'm nearly 40, at 30 I was very fit, so feel ashamed lol