I posted a couple of months ago about wierd heart palpatations while riding. I made an appt. with my doctor and he said it sounded like "premature heart beat" (where your heart is cruising along OK and then it has a double beat followed by a pause. He said it is not life threatening, but the pause is scary. He said it could be caused by stress or caffiene, among other things. I scheduled a stress test and passed without incident (the man who ran the treadmill said I had a slightly enlarged heart due to training). I have since cut way back on caffiene and tried to reduce my stress. So far, so good although I find it hard to relax while biking in 20 degree weather with a 15 mph headwind. Aaaaaauuuuummmm. PS. I also quit using my heart rate monitor on every ride. I was watching it more than the road.