Maybe you could think about ways of excercising your hand; for example i've seen those 2 metal balls that move around your hand. or maybe this thing i've seen that you squeeze and retract that builds the strength and muscle in your hand.
i would have a look at things that improve flexibility in the hand. also i'm not sure if this is relevant but is it the 360 controller - does the size too big causing you to strain your fingers ??