It's just your legs telling you to stop.For some reason, when I run, my calves have been tight as hell. I've been stretching them more because of it, and it doesn't seem to do anything. It's pretty much my whole lower leg, so like, the calf, shin and back of the knee. It's not a cramp, or a sharp pain even. It's just like, the muscle is being pulled really tight the whole time. It's really ******* with me. I can't get much more than two miles in because they literally get sore as I'm running.