When riding hard for a long period of time I can feel the muscles in my legs begin to like pulse. I can feel my calf's (that is probably spelled wrong) pulse and then shortly after cramp up. I have never had this happen to my quad because I tend to back off once it hits them. I just wanted to know if anyone else ever gets the muscle pulse, soon followed after by destroyed legs. I mean am I just not listening to my body and should slow down, or should I have no mercy (as I tend to) and just destroy my legs?