This week ended much better than it started. Tuesday's interval workout was a bit depressing, as I fell apart on both the second 1600 and the second 800. Even when I'm having a bad day, I usually negative split my workouts, both descending the pace of the workout and running negative splits within each interval. (if it's a bad day, I just run slower.) But Tuesday I fell apart on the last lap of the second 1600, and then did the same on the final 800.
That's unusual for me. Except when my iron (technically ferritin) is low.
And like that, a (admittedly dim) lightbulb lit up.
I'd last checked my ferritin in mid-January, about a week before my half. (I check it regularly, just to know what's normal for me, and also to get some warning if it's dropping). At that point, it was lower than I would like, but still in the "fine" range. I made a mental note to start supplementing. And then I forgot to, between traveling, heavy workload, blizzard, etc. (I think the fact that the half went so well also played a factor in my blowing it off).
But, looking back at my training log over the last 10 days, my hard runs have been on a downward trend, despite getting enough sleep, not pushing the speed, and not doing high mileage. Combine that with the positive splits in workouts, and the ferritin test from a month ago, and it wasn't a hard call to go on the iron supplements again.
(sidenote: though low ferritin is an issue for many runners, no one should just randomly decide that they need to start taking iron without checking with a professional first. There is a substantial subset of the population that has TOO much iron in their system (google hematochromatosis) - and taking more iron can be very risky. In my case, I know I don't have that issue, and have a history of low iron, so I'm comfortable taking supplements).
So - I started back up on the supplements on Tuesday, taking them twice a day with lunch and dinner. And by the weekend I was feeling and running better. Not truly peppy, but better. Perhaps it's the iron. Or perhaps it's the placebo effect. Or perhaps I just had a minor bug and this wasn't iron at all. But I've got more snap to my legs, and that's good.