American River 50, part 1. 2500' climb for the course. Started at 9-9:30 pace, settled into 8 or just sub-8 running pace after the first hour, which was still more like 9:00 overall pace with 3-4 minute breaks I took at each aid station, plus bushroom stops. Got to the 27.4 mark at 4:09:35, took a 13-min break. The paved bike trail (with shoulder) changed into a single-track at 30 miles, and I slowed to an about 12-min overall pace. The quads started to tighten at about 5:30 but got better by 6:30; the problem was no doubt due to the sub-3 hours of sleep I got after my Amtrak adventure, and because of the stupid bicycle stuff I did the week before. At about 6:50, things suddenly unraveled. The tendon started to hurt, there were a few cramps, and I got problems maintaining balance. But until the 7-hr mark, I was continuously passing people; I was only passed by 2 or 3. I ran/walked the next 4.5 miles to the 43.2 mile aid station and declared that I was quitting. I was way off my target of sub-8 hours, not feeling very well (but not really bad), and feared more problems with the tendon. It was 76 degrees. I was still just behind the top 100 in placing.