So says a new study --
http://time.com/3104455/more-exercise-isnt-always-better-study-shows/
It is based on data from heart attack survivors, but the results are being taken to apply more broadly. I have to say that, even if it is true generally, it wouldn't impact my mileage (about 50mpw). I already KNOW walking would be safer with almost as many health benefits, but nothing is like running.
What about you?