This year i started having a problem with my left leg going numb at  mid-o.. Always happens about 5 minutes before the end of a 20 min  session.. I'll start to barely notice it with not being able to pick up  my foot as good to downshift.. Then it progresses to can't pick my foot  up at all which is scary as hell coming off the back straight. And  eventually my whole leg feels asleep. I can't figure out exactly what it  could be (back, hip, etc..) Everyone that I've ridden with says my body  positioning is spot on, i do have vortex rears that are raised up and  back as far as they'll go.. But I've never had an issue with those on  the street (although I'm not hanging off like on the track) .. I would  have a P.T. I work with check it out but it's hard to exactly  troubleshoot something when the only time I have those symptoms is when  out on the track! Have any of you had problems with this??