I did my first century of the season yesterday. In the three+ years that I've been riding, I've been doing one to three centuries per year. I've bonked during a couple of them somewhere during the last fifty, but this year I had the strangest thing happen during the last 25 . . . When I stopped to check in at the 75-mile spot, a calf muscle seized up, just briefly, when I got off the bike . . . I ate, I drank, got back on and was feeling fine . . . but when we had to stop for a traffic light, one of my thigh muscles started cramping like crazy . . . We pulled over at the light -- where as luck would have it, there was a gas station with a convenience store -- to fill our bottles with more Gatorade (only water at the rest stops), and continued on. For the rest of the ride, my legs were fine as long as I kept spinning, but were prone to cramping if I stopped spinning, though by the time we pulled into the final stop, I had no problem at all. Anyone have any idea what's up with this . . . and how to avoid it two weeks from now when I do another century? BTW, this was the fastest century I've done -- averaging 18 mph! Not bad for a little old lady, huh?
Same thing has happened to me before. You said this was your fastest century ever. That is the clue. What I think happened to me and maybe happening to you is that your muscles ran out of the substances they need to operate efficently, mainly minerals and glycogen. I have have tried to avoid it by spinning easily for the first half or more of a long ride, then turning up the gas toward the end. When you ride in you anerobic zone for a long period of time your body uses Oxygen faster that it can get it back in. The longer you stay in that zone the harder it is to recover. You might also look at a www.ultracycling.com its a great site for century riders. Good luck