I've run down to like 11 and 12 on several occasions. Sometimes, particularly if I'm in the middle of something, I'll sort of keep at what I'm doing until I get really out of it. It hasn't happened too much lately but used to be pretty regularly. I also saw people turn orange and have plaid hair once, pounded my head on a concrete floor, handed baby daughter to MrsAcidRock and fell over into a bowl of dog food which flipped up and exploded all over the place (and was probably low carb too..), all sorts of hair-raising adventures. I've also hit the 30s like 2 miles into an 8 mile run and just soldiered on. That's probably not recommended either but can be done. Guitar Hero seems to really be horrible as it always takes me a while to get warmed up and then, by the time I get the hang of it and am like "ooh, I'm Slash", my legs disappear and I can't hear anything, sort of like the "going numb" you are talking about.