On our late Diagonale, heavy weather and headwinds meant that we had to ride 340 km, have a 2-hour rest, then 290 km with a 1-hour rest followed by 170 km. At around 250k of the second stint I began to have trouble holding up my head. Gradually this got worse until I was looking straight down at the handlebars with a fine prospect of the bottom bracket and gears. After every couple of minutes riding like this I could lift my head again for a glimpse ahead, like a swimmer thrusting up for air, and then it was down again for a while. I could also lift my head with a fist under my chin and steer with the other hand. The countryside was hilly, to say the least: belting downhill in this latter configuration was interesting. Fortunately the roads were mostly dead straight or I'd have been straight dead. Riding through Paris this way was also amusing.
Anyway, I've been told that the condition is known as
Shermer's Neck. Nice to know that I have a malady named after a somewhat noteworthy character but honestly, I'd rather he had kept it to himself.