I walk every morning and hit 80-80% of my max heart rate for parts of it. Walking can be quite good exercise, unless you live somewhere very flat. My V02 max continues to climb steadily 0.1/week like clockwork, and no running yet. Granted, it's got a ways to go, it's just barely above average, but still, walking is working.
That's a perspective I haven't heard before, though I see that Google somewhat agrees with that being a valid point of view. Though it does suggest higher speed with more intention is a distinction. In my mind, hiking is something I do on a trail. I walk around my neighborhood. This includes a couple of climbs of ~200 feet over the space of about four city blocks. Moderately steep, but entirely normal terrain for the area, and all on paved roads or sidewalks at ~3 mph. Never occurred to me to think of it as anything other than a good walk.
