Alright so today I took my Parker Wildfire XP and got a new bowstring put on it. The draw weight on this thing is 70 pounds and I could pull it back easily.. With my old stretched out string. Now I got this new string and I cant draw it back without aiming to the sky then aiming at the ground then getting a cramp. So I let down the weight on it and now I can get it back but my question is how am I supposed to build up the muscles required to draw back a 70 pound bow. I want to be able to use the full weight so I can get the best of the best out of my equipment before next season. So, How can I build my muscles built up to draw this thing full weight.