[Callers] Fragile dancers, safety policies

What do you do if you have dancers who are becoming frail, but do not seem to acknowledge it, and that you are concerned might fall and hurt themselves (or others) at an English country dance or contra? Particularly dancers who have danced for a long time and given much to the community, but just refuse to admit that they are becoming hazardous to themselves and others? We have some very good and much older dancers, slowing down but still quite capable, and it is not about these that I am speaking. I’m talking about a dancer that everyone watches with great anxiety, and who has been gently spoken to suggesting they only dance those dances that are identified (and we’ve started identifying them) as slow and simple. Did not take the hint and was rather affronted. Also, Does anyone have any safety policies? For example, that by participating in the dance, you are affirming that you believe yourself to be physically able to do it? Or language to that effect? Any advice? Martha