numb bum?

[johnakay]

this what I have now.
http://2009kawasakier-6f.blogspot.com/

[Triplerocky]

Just too curious.... I imagine that "numb bum" should be a bottom pain of some type, but no dictionary report a reasonable translation, so, exactly, what is it? just to extend my english knowledge.
Thank you.

sitting for long periods eg bike,it is then the bottom start to lose feeling of some sort hence numb and ache but it does become very painfull after a while.
the bottom in plain English is the bit you use when sitting down in other words your ass or arse

Thanks Johnny!! Now I know how to name that "absence" of b**ls, upper legs and both cheeks after I'm riding for a while !!