Some dogs simply love to run. I got chased by one at the height of my racing going down a decent hill. We saw each other simultaneously. I stepped on it. The dog started on the front door step of a large house set back a full suburban lot as I was crossing the walkway. Dog was two steps behind when I hit the lot corner! Beside me immediately, then just proceeded to pace me down the hill. No bark, no growl, no teeth. Just an easy run while I went as fast as I could go. Hill leveled out and he pulled up and trotted home. Work done. The whole time, we both knew who'd cross any finish line first. Humbling.

Years later my neighbor picked up one of those dogs. A whippet. Edit: A body hard as nails. And also loved to run.