I was shooting every day, several times a day for several months until a week ago. From time to time the 1st shot or two caused my draw hand to hurt (stiff). I also had a bit of soreness in the pectoral muscles around my sternum. No big deal, just an irritant. So, I took 3 days off shooting. The next time I shot the bow felt so much better! I felt stronger, the soreness was gone. I guess, like a weight lifter, alternating workouts gave muscles time to recuperate and strenghten. I do two types of isometric exercises when I'm being careful.
1. Curl the fingers of both hands and interlock them. YOu can pull the draw hand against the other as if you are drawing the bow. This warms up the muscles in readiness for the shot. You can do this in a blind, rocker, tree stand, etc.
2. Make a loop of string that when you measure the inside diameter is the same as your draw length. You can then put the bowhand in one end of the loop and the draw fingers in the other. You can practice your entire shot sequence putting more and more pressure on the string. This is the String Bow. This also warms up your mind for what a proper shot should feel like.