I wonder what is happening to my back lately. It's be aching for a few days. Not the very painful type, but it's like I have been thru a very heavy sport session. Paupau said this is due to my karting session lately...hmm ... come to think about it, these karts has no suspension (springs/dampers), my bum was soaking up all the impact when I went over the kerbs...hahaha... Or may be I have done too much driving lately. arghhh... I need to work on my core muscle, may be a fitness ball will do the trick....