I think there is another reason that exercise does not always cause my blood sugar to drop, even when I am doing a more moderate-intensity workout: I have basically adjusted my basal rates to account for morning exercise, and I am consistent in exercising almost daily. So, instead of constantly reducing my basal rate, I try to remember to increase it on my off days. Of course, with anything diabetes-related, things don't always work out as planned--there are still days when I have to eat 3 gels to get through an hour of exercise!
When I first start a new exercise type, or increase volume and/or intensity of my current regimen, I will typically notice an increase in insulin sensitivity, as manifested by more frequent low blood sugar (unless I catch on early and adjust my basal rates). This can be significant, especially initially; over a few weeks, the effect seems to be reduced, although I will still be more insulin sensitive than prior to the change in exercise (up to a point). I remember, when I first started doing triathlon, I had a couple hours in the afternoon where I had to shut my pump off. My body adapted to the changes and the effect did not last for more than a week or so; but still, I had an overall, significant decrease in my daily insulin dose that persisted. I had been running 6 days/week for years so initially, at least, it was primarily the change in exercise type that was responsible for the effect.
When this effect diminishes and my insulin needs increase a little, I see it as a sign that my body is becoming more efficient at the exercise and that my fitness is improving. Or maybe it's just time to take it up a notch again.
|bike class at the beginning|
Oh and now you can see, perhaps, why I want to have the power meter (and/or other fitness devices) and CGM all integrated. I won't go off on another rant right now since I already took care of that here!
And one more thing: I think this stuff also applies to athletes without diabetes. I am surprised that people haven't started using these tools to refine athletic performance. Seriously, people pay big bucks to save 10 grams on their wheel, which is absolutely meaningless if you don't fuel properly and get sub-optimal blood sugar during a race. It is really hard to nail down blood sugar levels unless you actually measure them. (For example, I have bonked with normal blood sugar.) And as luck would have it, there are plenty of tools to do so. I would love to see some top athletes show their data during races, for example. Bueller? Bueller? Anyone?
Addendum: I'd like to add a reminder that exercise can of course cause a drop in blood glucose, which can become life-threatening if treatment (i.e., a carbohydrate source or glucagon) is not available. I almost always have at least 50-75 g of fast-acting carbs with me, and more if I am exercising >1 hour or somewhere without quick access to a store etc. And I always bring along the CGM and/or BG meter. (I rely on the CGM alone for workouts <2-3 hours, but will bring the meter as well if I'm going longer.) Don't make fun of the bulging pockets on my jersey!