But a change from what? The day before, I ran to the gym and back - twice today's distance. The day before I ran to the park, did sprints, and jogged home.
In short, almost every run is different.
Yet I do have a routine. It isn't the route, the speed, the time I run, or the music (which I don't listen to).
What's routine is the discipline: to close the computer, get up from the desk, change into my jogging clothes, and hit the dry, crackly grass.
And it has similar results: muscle hypertrophy, cardiovascular health, and a quiet contentment.
In this, running is like a good artwork.
Of course it's not really an art: it doesn't express emotion, or coalesce experience into an arresting whole. It has little aesthetic value. It's a craft: what the Greeks called techne.
But the analogy stands. Like all fine art, it has diversity: different details, which keep me interested and alert. Yet it also has unity: forms that endure, despite the details; principles I grasp, internalise and apply.
Like art, jogging is also something I can enjoy alone, in my own time. And yet: sharing its beauty is the most natural thing in the world.