Everybody is different........you just need to build up the muscles.
If you can set up a short range target in your basement you can just shoot a couple dozen arrows a night simply working on getting stronger without having to worry about where teh arrow is going.

I shoot all the time so fatigue is generally never a factor. I'll have extended range sessions with my 61# recurve where I might shoot well over 100 arrows at various ranges and my last arrow will be just as strng as the first.

It takes some time to build up archery muscles but some basic core and upper body exercise will help as well. Sit-ups, pull ups, push-ups shoulder raises etc.