I grew up doing a fair amount of manual labor, walking long distances, and other repetitive tasks for hours on end (way before I had portable music) like most others. I always enjoyed finding a rhythm and playing around with variations of it in such instances. In retrospect, I've played with the idea that you are your own metronome so what I would write during these periods had a meter to it, maybe several, and it was almost like a secondary stage to identify these subtle changes and separate them into independent entities.
During this stage, some things I would write would just propel me into a mission to find a beat to lay with it. Often times unsuccessfully and it would be relegated to the grey matter filing cabinet only to be rediscovered with the most immature smirk possible some time later. Redemption.
On the flip side, walking circles to a beat writing with structure seems so seamless after pressing play on a product.