That was quite an experience.
I've been meaning to have ago at racing for a while, but due to one reason or another missed all of the small local races over the winter here (here being down near Montpellier).
So I signed up for the second leg of the "Offroad Challenge" : 38km, later measured to be 41, and I finished with 43 on the counter... a single long loop through the hills near Nimes. Loads of singletrack, some freshly cut and a pretty good atmosphere. Mostly confirmed fast racer types, a few guys like me just having a go and even a handful of people on tandems which just looks nuts.
It was pretty much as I expected. Everyone went off like a rocket, but had spread well out by the time the singletrack arrived. The course wasn't really that technical, certainly none of it was as hard as some of the spicier sections on the local "Randos" that I've done. However, staying in the red for over 36kms seemed to make up for this. At the 37th kilometre I was struck down by the most amazing double-thigh cramp that I have ever had. Both of the inner bits (looking down) just above the knee mutinied at the same time. They swelled up to about twice the normal size and locked both my knees backwards. I just had time to stuff my bike into the bushes and grab a tree. For what felt like an age but was probably only a few minutes I could do nothing except rub my thighs and whimper "Crampes" at all the people who I'd worked hard to keep ahead of as they glided past. I couldn't even sit down and stood there wondering what to do. Eventually normal size and some flexion returned and I could stretch out and then get moving. The final 6km were very slow as I had no power for the climbs, or the flats and just hung on for the descents.
Thinking about it, I suspect that it's just a lack of specific training that got me. I ride a fair bit, and have no problem going out for a few hours, but at an easier pace. Today was the first time I've ever gone so hard for over two hours without stopping.
Interesting though - a completely different experience to my normal riding. I might do another some time. Maybe a shorter one.