That's all better advice than this, but if you want to give it a try, and it doesn't hurt, give it a go:

Do push-ups. It's pretty close to the reverse exercise to drawing a bow. You don't have to do a lot. Say do three, and shoot your bow once or twice, and give it two days, then try again. This is the miracle cure for ballancing your shoulder, but it won't cure serious problems, or probably many minor things that aren't specificaly caused by shooting a bow (your moose loading example).

Also, if you are in any doubt about form, take a shooting class, and make sure you are doing everything correctly, and aren't overbowed. I would even take a "compound" course say the PSE course. I think they are interested in all sorts of shooters.

Also, get a very light rubber scarf thing, or surgical tube, and do a bunch of warm-up exercises before shooting. Take it into the woods with you on stand, and if you don't see an animal coming, do a few warm-ups. Do them on the line. The Olympic shooters do this all the time to keep everything warmed up. Shooting a bow puts very high stress on a set of muscles most of us hardly use. A classic situation requiring warm-up.