I've run both days this weekend, just as I have for many weekends before. Even the same routes! Both runs have felt very hard work, my legs have been heavy and lacking power whilst overall I've felt simply tired. I pushed on, walked as necessary and both days I've completed at pretty much the usual pace.
I wonder if I can blame swimming for my lethargy, at least in part, as this is the first week that I've swum for over an hour in the week since May. Some of that swimming was done with the ToyBuoy but it was still exercise and I have been trying to 'engage the core' and 'lift my legs' throughout so it will have had some impact on me. It is notable that my faster Sunday runs tend to be when I haven't done a run on Saturday; the back-to-back arrangement is tiring.
It's also been arduous at work and I've even had to do some tasks over the weekend, which is quite unusual for me, so I suspect my 'stress bucket' is overflowing.