Why Do I Get Painful Muscle Cramps?

Here is a  very interesting article on the causes of muscle cramps:

http://www.theglobeandmail.com/life/health/why-do-i-get-painful-muscle-cramps-when-i-work-out/article1632891/

The article explains muscle cramps being caused by imbalance between nervous impulses, a sudden loss of electrolytes, and a poor training schedule.