I had a strange thing happen after my run yesterday. My legs were slightly stiff. Nothing serious. This was strange because I usually don't have a problem with stiffness after a run. We used to think that stiffness was due to an accumulation of lactic acid in ones body, but now the sports doctors say that isn't so; the stiffness is due to small tears in the muscle fiber.
I felt fine after my fartleks on Saturday, and I felt fine on Sunday and on Monday before my run. So, the stiffness seems to be due to my Monday run. I did a number of cadence drills, but the increase in speed during the drills was very slight.
As a result of the stiffness, I'm taking a rest day today. Also, I was still tired after the combination of fartleks on Saturday and cadence drills on Monday.