I was doing a practice crit the other day, a very hard one at that (I'm a 4 and there were 1's and 2's up front driving the peloton). I was fatigued due to a 2-hour warm up with the team. We did the long warmup since it was, after all, just a training crit. I had also ridden a decent 50 mi tempo ride the day before. No doubt, I was fatigued.
At any rate, in the latter half of the race my upper lip was spasming. It hasn't happened since. What causes spasms in unrelated parts of the body?