I'm actually pretty decently fit.
I also play piano competitively, does that make any difference? idk, but I use both my arms and wrist a lot.
Anyways, that was more of a comparative statement. It's more tiring then if I just use my fingers and my wrist. I could essentially say the same thing to you guys about your wrists. I honestly don't find it tiring to use my wrist.
Edit: adding on... when using my small tablet area my wrist barely moves, it's mostly my fingers (my pinky and my ring finger are placed firmly on the tablet). I don't really know if that makes a huge difference or if other people do that as well.