Ah half marathon training! It seems like it can only be good for you and your body. You’re torching calories, toning up those legs, and all that exercise should totally help control my blood sugars, right?
Um. Not really. At least, not right now while I’m getting used to running longer distances again. It’s been two years since my last half marathon, and although I’ve done a variety of sports and events since then (plus one three-month seemingly endless walk around Southeast Asia) I have not run longer than about 45 minutes in a veeeery long time. So on Saturday, I was in for a rude awakening in the BG department after I clocked a five mile training run.
I started off at a respectable 95 mg/dL, and cranked my basals down by 50%. I held steady for while, but just past the halfway point, the arrow on my CGM started to slant downwards, and every five minutes I was dropping lower. When I hit 75mg/dL, I decided to crack open a GU pack now rather than later to avoid a steeper low. Plus, I dropped my basals by 80%. I think I was dropping faster than I thought though, because another five minutes past and I was feeling pretty light-headed and tired (not that running can’t do that to you on it’s own, because it does, but you all know what I mean!). Knowing I’d just taken down 18 grams of CHO though, I felt comfortable pressing on, and I was back in the 80s and rising by the time I turned on my block. I felt safe again and satisfied that I’d still made it through the run despite the low.
That is, under the 80 turned into 180mg/dL, and then 230, and finally peaked at 275mg/dL by the time I was done with lunch. Ick. I have to blame my liver partially, since I did the training run on an empty stomach, and also the GU pack with a few more grams of CHO than was probably needed. And I had turned my basals down more than required I think. To top it all off, I didn’t bolus early enough for my lunch and that contributed to the meteoric rise. I rage bolused the stubborn high back down, and, as rage boluses tend to do, they all caught up with each other around 4pm when I crashed hard to a low under 45mg/dL. Not only had I corrected too much, but I was more sensitive to the insulin because of my long run that morning, which I had not taken in to account as I corrected the high.
In my sweaty, low fog, I reminded myself that with training for a distance event, subtle changes can have a huge effect. The goal here is to tweak things ever so slightly in one direction, not all at once with one giant swoop. It’s like going to power steering after having a regular wheel – you don’t need a ton of force to change the course of your BGs when you’re dealing with a ton of exercise. Small amounts of carb and insulin can make all the difference, while large amounts of either can inversely create massive problems.
As I head in to the next few weeks of training, I’ll need to work on some precision management of my numbers as I build mileage. The good news is, I have the tools to do it – pump, CGM, quick acting carbs, and the bat belt to carry it all in. Such a good look, right? Ha.