If it's not one of the frequency based zappers sold here it should be ok. I was very unaware of their lethality before this time. I would distrust any zapper from the source selling the frequency ones--they could be tampered with. Good luck to you---but if you feel that intense muscle bunching--stop immediately and find a different source for your zapper. And get Dr. Clark's book, 'cure for all diseases', free download here, for the proper protocol and usage. She covers it well.