Most people are familiar with the concept of Circadian rhythm, but I would argue that this is too shortsighted a view of human rhythms. After having a generally positive, upbeat week, I'm finding today is more down. Not down in the sense of depressed or negative, but just lacking in energy. I've had good workouts all week, but today my lifting frankly sucked rocks. It's definitely normal to have negative workouts like this -- you can't always be at peak energy -- but it's nonetheless frustrating.
What I really wonder is why we rarely seem to see studies about these mid-tier cycles? I've read about life rhythms matching with the seasons, and have also of course read of Circadian rhythm, but there seem to be regular sine waves in between that should also be considered. Anyway, just food for thought.
The good news is that this weekend promises to have some of the best football we've seen all season. Maybe that will help restore my energy. Of course, as for the aches and creaks, it's hard to say. :)