The explanation makes sense to me. It's called contracoup, if I have the right term. Force from behind makes the brain hit the front of the skull, in a case like this. Though I don't think it's quite as bad that way as if it's actual blunt force trauma like a hit. But I probably only know because I'm always watching Discovery Health LOL Anyway, yikes...it did have to be scary. Good thing he wasn't badly hurt. And less important, good that filming was done...not sure how they'd have managed things with him resting afterward. Like the pics The Twitter announced the seemingly annual Joe's concert here...man I wish I could get there one year.