in my early studies and in university I am still learning that the muscle cramp is a result of O2 supplement reduction which make completeness in crips cycle and the a high production for the lactic acid makes the muscle cramp 

but i have read about an article which say that the muscle cramp is not because the lactic acid it is because for muscular cuts happens in the level of the muscle protein like actine or myocine  and it is the same for the Athletes when they make high exhausting efforts they feel with muscular cramp because for this cuts