A quick cramp story. I continued to ride my MTB during my cramping period. I would either notice one coming on and stop to work it out, or they would come after a ride. One time I had just arrived, and came to a small downed tree across the trail. Just as I stood up to power the rear wheel over it, a cramp bit me and stopped me dead, half over. I fell to the right, over about a 10' bank to the river.
As I went over I heard/felt a loud pop, and had to grab my bike as it went by to keep it from going on into the river. The pop was apparently my hamstring I guess caused by the cramp getting pulled out as I fell. I hobbled to a place where I could climb out, but couldn't get my bike up with me, so I was stuck there for what seemed like an hour waiting on someone to ride by who would stop to help.
Once out it was a fairly short way to my truck. If I'd been deep in the woods I would've been really screwed. I had to call for someone to come and drive me and the truck home because I didn't really fit under the steering wheel with the way I had to hold my leg. Before long the back of my leg was black and blue from the top where my butt ends to the bottom of my foot. The worst part was finding a way to sit on the toilet. There isn't much that can be done for a hamstring injury other than to tough it out, and It still gives me trouble.