That's an injury.
https://www.outsideonline.com/239882...drome-research
6 years ago I wound up suffering overtraining syndrome, which then got wildly out of control. For me it went on like this.
I came down with the flu, symptoms kicked in during the first race of the season.
A week after the flu I panicked about the lost fitness and without recovering enough from the flu, I started the equivalent of Base 2 -- 20-25 hours a week. By week four I could barely turn the cranks on my bike. I should have just given myself more time off to recover.