Why is my leg cramping?

Considering most cases of muscle cramping come from the lack of potassium but it could also be due to other causes as well. Do you eat before training? This could be the cause of cramping. Do you or are you stretching properly? Last time I didn't stretch properly (half stretched because the coach was almost on the field and we had to be done before he got there) my leg cramped up so bad. However, if its not because you ate right before or you stretched half way, then it is your poor lack of potassium. Whenever you get a cramp though, flex that muscle the other way.