Have you ever hurt yourself or had sore muscles from video games? I'm sure many had some pain.
Some examples are getting carpal tunnel from too much time on the CPU. I actually got one from playing and hanging out on the Fungi Forums.
I also got a blister on the palm of my hand from games on the N64 that required you to rotate the control stick. An example is from Mario Party. There's a game where you have to rotate the stick fast. What do you do? Most people would use their finger but I found a way to rotate faster. put the stick on the palm of your hand and rotate your hand like you're cleaning a window very fast or something. I was able to beat the CPU, but i used this technique too much and I got a blister right on the palm of my hand.
I got another blister on the GC controller. When you have to press A a lot in a limited time, I rake the controller. I take the part of my hand between the joint after the knuckles and rub it on the A button. Then I press A really fast. The harder I do it, the faster. You can do 3/4 as much as a turbo controller if you do it really hard. But prolonged use will make a blister.