Anybody who has sat through a Nintendo marathon will know that , after a while, your thumb starts to get sore from pushing the buttons so much, and you normally stop playing . However, if you were a real fanatic and couldn’t cope with not being able to score one more goal or blast the evil empire, the chances are that you would carry on playing anyway. And what would happen to your thumb then? It would eventually grow much stronger, exactly what’s happened in various parts of the world according to a new study