walking better than running?

I continue to  learn:

The problem I see with this point of view is the testimony of dedicated runners who claim to experience a "runner's high" while running. For these folks, running is a pleasurable experience, which seems to go against the idea that the body gets a major hit of cortisol during the run. If the runner's high comes from endorphins (associated with pleasure), then that would probably counteract any negative effects from cortisol. I'm not saying the lady is flat-out wrong, but I get the feeling her explanation needs to be unpacked a bit more.