Vince - Never been able to get over Jim Fixx (and bad knees that I am trying to save).
Over the couple decades I've been running I have, quite regularly, been lectured about
how bad it is for me, usually by not just non-runners, but non-exercisers.
Yes, any activity can be done to excess and even in my own running community I can cite runners who, IMO, damaged themselves over the years. These are people who did not just run, they raced. I am a runner, not a racer. I can run far but I've never been interested in runner fast.
As for Jim Fixx, he may have made running popular but that is about
all I know about
him. If I was going to subscribe to any running guru it would be Jeff Galloway. He is all about
running for fitness and staying injury free. I like his book "Run Until You're 100." I plan to do that just to see what happens after that.
And if I had to stop running, swimming would be my go to replacement. It's non-impact and gets the whole body in motion.