Foot cramps

I've just gotten back into blading after a decent break (Like 7 years or something) and everytime I go for a skate I don't seem to be able to go for more than half an hour without getting cramps in my feet, I assume it's because my body is still tensing up as I'm not used to being on the skates. I was wondering if anyone had any advice on how to stop the cramping, or is it just a case of getting used to skating again and letting my body relax?