Extreme juggling

Here is a man I saw in Covent Garden last night. He is juggling running chainsaws. I will say that again. He is juggling running chainsaws:

Juggling running chainsaws

I would like to know how you practice such a task.

This topic actually came up on a recent SGU, and the juggler interviewee was asked if he knew of anything more extreme. He mentioned a guy who juggles 100,000V stun guns. Like this:

I suppose it’s less extreme than the chainsaw in that catching the wrong end of a stun gun will knock you out, rather than take you out. That said, he did tricks. Tricks! That’s just insane.