I was a big runner up to about 4 years ago. The goal was to run a marathon, but a persistent stress fracture forced me to reconsider the amout of running I did. I later found out that my back is so whacked that it was causing mis-alignment of my hips and therefore the cause of my constant right foot/ankle/knee pain.
Over the last two years, I've turned to hour-long (4 mile) walks and I've found that I really enjoy them and the pain is non-existent.
This year, my wife and I have started a habit of getting up at 4:45am 3 times a week to go on a 4 mile walk with the dog. We love our time walking. This is an activity that we both can do well into our retirement.
Half Sigma / Lion of the Blogosphere is always good at pointing every time a person dies at a marathon race. And, yes, taken in isolation, most people think a death at a marathon race is very rare. But think about this: when was the last time you remember someone dying in football, baseball or basketball? Cycling? The only example I can recall is Len Bias. Whereas, if you google 'marathon deaths', you get quite a few articles and examples.
Anyway - the whole point of the post was to point out another study that bolsters the opinion that walking is better than running. And by "better" I mean it is good for you and sustainable. You get all the benefits of running without the stress on your body and heart.
Link: Brisk Walking Equals Running for Heart Health: Study