A couple weeks ago, while talking with someone I hadn't seen in a while (about 50 pounds ago, when I was running 50+ miles a week, and still lifting, but significantly less volume and intensity), he decided to give me some unsolicited training advice in the middle of the otherwise unrelated conversation:
"Don't go heavy", he said.
"What do you mean?", I asked.
"With the weights. Don't go heavy."
"Well, it's waaay too late for that. Why do you say that?"
"Because my doctor told me that lifting heavy weights is bad for you. He told me to stop going heavy, and not try to gain more muscle. Because the more you weigh, the harder your heart has to work."
"If were you, I'd start looking for another doctor."
As you can imagine, it went all downhill from there. The sad thing is that he already has a good amount of muscle mass (a fairly lean 198 pounds at 5'11") at the ripe age of 55. His doctor has essentially told him to his best course of action is to undo all the work and progress that's served him very well up to this point.