Is there a type of exercise or massage for artists that draw a lot?

[asdfghjkl]

My hand cramps when I draw too much and gets tired.
Plus, I hate the fact that my tendons always crack when i stretch my fingers back. I heard that that gives you arthritis?? HELP? :I

 

[Risie?Roo]

it takes me weeks to complete a pic at a time and by the time i'm done my whole hand is tense. i usually take a few days break just to give myself a chance to catch myself. i have tried to two chinese medicine balls (you put them in your palms and circle them around each other) but i find that that can sometimes add to the problem. so yeh, a break is usually the only thing to work.