> But as a distance runner, I have always wondered if that is a form of meditation.
The way I think about this is that there's an important difference between meditation (as a noun) vs. meditative (as an adjective).
Meditation, when you're doing it, is the only thing you're doing, or at least attempting to do.
I've gone on multiple-day camping trips on my motorcycle, when it's just me and my bike out in the middle of nowhere. I find that very meditative, in what I imagine is similar to what you feel with long-distance running. There's a part of my brain engaged with controlling my body and four limbs, but also a part of my brain that's not really engaged at all and is free to wander.
That's meditative, but that's not meditation. If I closed my eyes for a few minutes while riding my motorcycle, my happiness would decrease significantly.
This isn't to say that one is better than the other. You could meditate and never do any meditative activities, or you could do meditative activities without ever once meditating. The best option, as usual, is probably a moderate mix of both of them.