since my removal, exercise has been a must!!! i feel soooo much better physically. when i first got mirena removed i also took 10 minute walks to clear my mind. i still take walks if i am grumpy or upset. then i feel better. i have figured out if i dont exercise i get facial hair and my pms is worse. the more i exercise the less pms symptoms i have. i definitely agree with your theory that exercise may help regulate your periods.