Well this kind of wierd. I have just googled to see if anyone has had a similar thing happen and ended up here ... I am a guy, and experienced exactly the same feelings when climbing the ropes in gym at school when I was 10, etc. So I made sure I attended classes regularly without knowing the real reason! Anyway, I now experience the same sensation after strenuous excercise at the gym - normally after spinning or cycling. I asked my partner if she had experienced anything similar and she just gave me that glazed look to say .... 'what are you on...'
At least I am not alone out there now!