So we have not discussed the reason for the spike yet. That is not a fueling issue, but a hormonal response to a hard effort.
I will get to that in a bit.
Okay, so tell me how your pace for a 5k compares to the HIIT effort that causes you to spike. I imagine your HIIT intervals are much shorter, so they can be faster. Is your HIIT significantly harder than your overall 5k effort?
The thing that spikes you is when your body gets to a certain level of effort, and then it cries out for help…
Intense exercise causes the release of hormones that help you fuel the activity. Well, they would help you if only your pancreas would participate like it is supposed to!
At a certain higher level of exercise intensity (or even from emotional stress like an argument or from nervousness), your body releases hormones - epinephrine (adrenaline), norepinephrine, and cortisol. Your heart rate and blood pressure increase, the amount of oxygen flowing to the tissues increases, and your liver’s glycogen stores are released to give you fuel.
You have probably heard of the “fight or flight” response.
Imagine you are running along in the woods at an easy pace. Your body is able to fuel it with glycogen, carbs from food you recently ate, and fat metabolism.
Suddenly a big bear appears and starts chasing you.
Your body would want to make sure you had plenty of fuel to run away! (Remember the earlier conversation about how you can go much faster burning glucose than burning fat.)
Let’s make sure Keely has enough glucose to burn so she can get away from that bear! These hormones will trigger her liver to release glucose immediately. And then her pancreas will release the right amount of insulin and she can use the glucose to fuel her escape!
Great plan the body has, right? Except your pancreas just isn’t cooperating. Everything else is working the way it’s supposed to. Except your pancreas.
Ultimately what you see is an immediate rise in your blood sugar.
So there is a pace or effort or point that will trigger those hormones. It will depend on many things - your overall conditioning, your level of fatigue, the amount of training you are doing at those paces, etc. That level of effort is different for everyone.
Once you know what pace and distance causes your body to scream that it is being chased by a bear, you will know when you need to dose and how much.
(Oh, and as far as aerobic/anaerobic, you can imagine that if you were running from a bear, you would be moving toward the anaerobic area of intensity. But it is a little more complicated than that. A 100 meter dash is almost completely anaerobic, but that wouldn’t spike you, because it is so short. Running a mile as fast as you could would be about 80% aerobic, but that WOULD spike you! So there are 2 things at play - speed and duration.)
It depends on when the spike hits you, and how predictable it is. The spike might be very quick, in which case a 20% temp is not going to do a whole lot to help you.
For me, spikes happen quickly. So I go with boluses.
It would be helpful for you to track the spike with some BG tests to see when it happens. If you are looking at your Dexcom, it might appear more gradual. But in reality, it might be very sudden.
For HIIT, you can actually do your BG tests during the rest phases. Get a real good picture of it. Much better than dealing with the Dexcom delay.
Do you have one of these?
https://www.amazon.com/Contour-Smart-Meter-Monitoring-System/dp/B06W53ZLTK/
Sorry, I threw a bunch of new things out there. Does this stuff make sense?
I’ve had a lot of practice.