alleviates cramps. Try it!
And since we're on the subject...
If you're like me, exercise is usually the last thing you will feel like doing when you are dealing with PMS. In my case, it's PMDD which is premenstrual dysphoric disorder. If you're not familiar with it, it just means I get mega PMS-ie during my period, but also the week before. I know, my poor husband right? Anyway, my birth control helps a ton with the mood swings and such, but I've also found exercise helps! It seems that the release of serotonin and other 'good' chemicals which occur through exercise will actually help you with the symptoms of PMS. So Mom, all those times you told me to go run because it would make me feel better when I was feeling crappy, you were right!
So, run and be happy!