In day one of analyzing my lack of energy during mid-week runs, I'm taking a gander at my overall training effort. Here's what Coach Jenny (via Ask Coach Jenny) had to say:
Training Effort. Are you training by effort or pace? A common mistake is to train too fast or too hard which leads to a slower recovery process. This is especially true when training in the record heat this summer. Invest in training at a truly easy, conversational effort for your long runs and let your pace be only the outcome. Avoid worrying about pace, as the long run is all about teaching your body to run longer and stronger. This is also the case when training during the week. If it is 85 degrees and humid, your normal running pace will feel much harder (more taxing). Train by your effort (how you feel), and you'll get in a quality workout, recover faster, and regain your energy.
Hmm. Admittedly, neither pace nor effort has been a huge concern of mine. I've been more focused on simply moving, and not necessarily the quality of each run. There are certainly times when I force myself to step it up and squeeze in a few sprints to awaken my muscles and ensure that I walk funny the next day, but for the most part, I stick to a "truly easy, conversational effort" with both my long and mid-week runs. I mostly DO "train by my effort" and how I feel, which is exactly why my mid-week runs are so sluggish... because I feel SLOOOOOW.
Alas, I fear that Training Effort is most likely not the culprit.