welcome to the board I had the same problem when I got my first bow the reason I think is over bowing myself. 70lbs may not be a lot for some people but you use muscles that you don't always use and if your muscles are built up it could also be that the motion of pulling your bow back is new to them. To get rid of the pain I had to lower my bow draw weight take a few days off and then when I did shoot I just shot less arrows until my muscles got used to the motion and got stronger and always streched which seemed to help. hope this all makes sense. good luck.