Marianne's conversion, I took her on her longest ride yet as a fixed gear - 28 miles. For the first 20 miles, everything was fine. The bike's geometry has never been the most comfortable, but as a fixed gear it felt better than ever and I was pedaling happily. But then, with just 8 miles to go, I suddenly became aware of a rapidly growing discomfort - not just in one area, but in several: in my shoulders, arms, back, pelvis, joints - pain seemed to be everywhere and it attacked me all at once. By the time I got home, I felt as if I had been run over by a train. I took some Ibuprofen and expected it would go away in the morning. But when I tried to ride my vintage Raleigh the next day, I felt the same pain immediately and barely managed to cycle to my destination a mere mile from home.
My working hypothesis of what happened is that while riding Marianne, my legs grew tired of the fixed gear pedaling, and without realising it I began to put more stress on my arms, hands, butt, and everything else. And because the mixte is semi-upright, this damaged some joints in a way that the pain only shows up in the upright position, but not in a leaned-over position. Does that make any sense as a possibility?