I agree with Karin for the most part Debbie, however, I think the problem lies in the fact that many group fitness certifications are self-study.
Too, some gyms on their website have the biography of the instructor online. In addition, when a new member joins an informed consent is generally filled out.
Hopefully, it has been reviewed and the new client has been risk assessed. If the person is a risk client, he/she would have had to produce a release from their physical saying it’s okay for the person to participate in moderate to vigorous physical activity.
Often in gyms, classes at peak time are back to back. People are hustling in instructors are collecting their music, ipods, water bottle, etc. and there is little time for what I believe is just good old-fashioned manners.
However, to answer your question, I’ve never seen a national standard for group fitness instructors.