Here's what worked real well for me. I usually shoot bows in the 50-60 range, so in order to increase my shooting comfort, I got myself a bow in the 35 lb range and shot every day, even in the rain, I used a picnic tent to cover me. With the light weight bow I could easily shoot 200 arrows everyday. What that did for me is it allowed me to use the muscles I needed to without strain. It allowed me to create a solid, strong form. All of which helped me shoot my heavier bow with total comfort.

(Edit - My post was all about P90X, and then I realized I was getting too far away from shooters forum        so I deleted my post)

Very few muscles that you work out in a gym will actually build shooting muscles.  work out by all means.  I do. Get a form master to work on shooting muscles.  If you are doing it right its your bow arm that should start shaking first when hold a full draw.

Stay away from heavy weight workouts.... not worth it. Any experienced and knowledgable trainer, therapist, and physiologist will endorse moderate rate and increasing technical difficulty rather than weight, kind of like the p90x system.

And the muscles you build in a gym DO translate into muscles used to draw a bow, I have no idea where guys get that from.

Whatever you decide to do maintain about 3 sets of 12. Between 1-2 minutes between each set. This is the ideal level of intensity for your goal.

Plus this will help to eliminate unbalance your muscle structure of your torso. An embalance can create huge problems. I think alot of people say that shooting a heavy bow hurt their should when in fact it was lop sided strength in their back and shoulders that strained and tore muscles and ligaments

Go to Marine Corps boot camp.    All joking aside, exercises using your own body weight are very beneficial. At 47 I still go to the gym and in addition to free weights I incorporate exercises with my body weight. Exercising to shoot a bow is good, exercising to improve the quality of life is great!!

I do 20 push ups, pull ups, and sit ups every morning and night and it really makes a difference.  by the way I get all my arrow wraps from onestringer.      

Simply pushups and pullups. Unless of course, you're interested in a gym membership.

But I tell ya, bodyweight exercises should NOT be underestimated. As long as you use full range of motion, meaning you go all the way up, and all the way down. Perform the concentric phase explosively, and lower yourself for no more or no less than 1-2 seconds.

If you're interested, I can teach you and easy, non-draining and very progressive way to perform bodyweight exercises. Just tap me on the shoulder  

Personally I like therabands to keep in decent archery shape. But I'm not sure how well they work for actually building muscle.

Not very well. The most efficient way to build size and strength, is through weight-training.

Late last year, I bought a pair of "traditional" dumbbells. I keep them on my side of our walk-in closet so I remember to use them each morning and evening. I do 10 repetitions each of miltary presses & bent over rowing. I started out with with a pair of 35 lbers & I'm now up to 55 lbers. I have extra plates to go up to 60 lbs & I may stop there.  I also use Bow Fit heavy rubber tubing device. It helps with my flexibilty as well as building strenth. I'm really surprised at how fast my strength is coming back. I hadn't lifted weights for amost 30 years.

I've been doing this as much for hanging treestands as for shooting my bow. An older dude like me needs to keep up his strength to hang stands & screw-in steps.

I do pushups,pullups,bardips,crunches and hike alot of miles! I don't have the desire to lift heavy weight or bodybuild and I don't pull real heavy bows, all my bows are 55# but I can pull them back and hold them comfortably if I have to, what ever you do stick with it and have fun because if you don't have fun it becomes a job and makes it hard to continue!! just my 2 cents, Jason