Why do your legs cramp up?

Vitamin E has apparently been proven to have substantial benefits for a high percentage of people with night cramps. I experienced night cramping in lower legs and feet for a couple of years. Severity ranged from mild (none to one per night) to severe (> 10 per night requiring me to get out of bed for relief). I found an internet post that mentioned Vitamin E after going through a full week of severe night cramps. I started that day with two 400 I.U. vitamins per day and experienced an immediate reduction in cramping frequency and intensity. It has now been two months since I started vitamin E. I am sleeping peacefully through the night cramp free!! I can even stretch in bed when waking up and in the past that would have triggered immediate cramping. I reduced dosage to one Vitamin E tablet per day two days ago with no recurrence of cramping so far. I am a 51 year old Caucasian man in reasonably good physical condition (exercise moderately 2 - 3 times per week) that takes 10 mg of Simvastatin per day for moderately elevated chloresterol. I had previously tried stretching legs / feet before bed (which helped some) staying well hydrated with water and / or Gatorade (helped some if I had been particularly active and was dehydrated), and salt (no apparent relief). The night cramps I had been experiencing were different than exercise induced cramping from excessive sports when I was younger (those were thigh / calf typically and were more likely during the activity, but occasionally occurred at night). My night cramps were anywhere from calf, to front of shin area, to top of foot, toes, etc. For me, Vitamin E has had a huge beneficial impact. I don't know how it helps, but it has immensely. Since beginning taking Vitamin E, I have averaged less than one night cramp a week that requires me to get out of bed. Before the treatment, that average would have been closer to 15 per week, .... and it had been > 40 the week before I started.