I got fitted a month ago my p3sl. I was running a 100 mm stem with a 7 degree and upgrade to a 120mm stem with a 17 degree a week later. In the three weeks building up to my race, I rode over 300 miles with that stem on. About 250 in aero position with no back problems. I shipped my bike out to the race destination and taped my seat location. I test rode the bIke for 20mins the day before race with no obvious problems and adjusted my aero bars to what I felt was comfortable. (I run Easton aero tt).Between mile 25-30 my back seized up and slowed my pace down as I could only maintain aero position a minute at time. The transition to run was brutal. I could only take baby steps while putting on my shoe and running.. I had to ice my back the whole way.it was my worst rub by 30mins.Any advise on what adjustments to make on my bike. Seat higher or lower etc?
Please only insightful feedback. Thanks.