I just tried this www.powerballs.com and in less than 5 minutes my forearms were screamin like you cant believe! The coolest thing is that it has a RPM counter so you John can keep tabs on who has the greatest power ball stats : )
You have to watch the world record being broken. It is kind of weird, strange, funny. The guy is struggling to hold onto that little ball. Its crazy. I would not buy one for $50 but I would for $30 just to try it.