Good answers already!

I'd also add that not only chemicals (maybe also ones used to get impressions done, hmm?) but also stress can leach magnesium & calcium & zinc & other minerals from your body... & guess what a symptom of too little magnesium &/or calcium is - cramping! & tense muscles etc.

so it could be a combination of factors really..
I would suggest supplementing with magnesium/calcium or eating foods rich with them aferwards.. may really make a difference..