RE: A serious question... I promise
Well an exercise you can do is a seated row or take a dumbell and bend at the waist and lift the weight the way you would draw a bow. I'm not sure what they call this. If that bothers you back find a bench to lay flat on you stomack and pull the dumbell up like you would pulling the bow.
This gives you th opertunity to warm up. If your going to shoot you can do this with light weights before pulling your bow. This will help build up you muscles with out injuring yourself more. Ultimately you bow is the exact thing you need to use but if you want to build up strength you'll be better off working up to it. This will give your muscles time to get blood flowing which helps build muscle.
I suggest trying it with light weights maybe 5 lbs. Do 15 reps then go to 10 and do 15 more... then 20 etc. If you belong to a gym they have all the dumbells you'll need. Ask a trainer if need be and they will show you how to do that particular exercize. Maybe someone else knows the name of the one I'm refering to.
Turn that bow down too. That way you can build back to the 50 lbs.