Look up Dr. Roger Bannister. He was one of the first "highly credentialed" ones. His biggest problem perhaps was overcoming "personal bias" in the results, since he was his own guinea pig.
There was a lot of research, and quite a few papers written, getting to the first "four-minute mile." Some of the work was a little "opinionated," but some really solid labwork was done.
Of course that's sort of starting at the beginning, and a lot more is available now, but if you're doing serious research at least a little bit of the history usually should be part of it.