Very good summary of factors!
Some ways of looking at it, depending on the type of run, distance, and intensity:
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Your body can only oxidize a certain amount of carbs during exercise. The general rule-of-thumb is no more than 1 gram per minute (but actually you can increase this to 1.75 g/min using different substrates such as combining fructose and glucose. Topic for another day!). All the other carbs will hit later.
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The max rate of oxidation can be reduced even more with higher intensity exercise. The harder your legs are working, the less your body will prioritize digestion.
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Even if you are keeping the same pace, your body might need to work harder the longer you are running at that particular pace. (A good topic to discuss sometimes - Pace:HeartRate ratio!) So later in the run, there might be even a slower oxidation of carbs.
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Just as described above, later in the run - even at the same pace - if you are getting more tired, you can be working harder. This can increase the effect of adrenaline, and that can cause your BG to spike up.
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And of course, as you mentioned, no basal or less basal for a length of time and you might spike from that.
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Alternatively, if you get tired and slow down later in the run and your intensity decreases, a lot of the carbs you had earlier will start to kick in!
The reason a formulaic approach does not work is that a run is rarely by formula. There are so many different factors to consider - intensity, Pace:HR, effort, distance, adrenaline, oxidation rate of carbs, etc…
@LarissaW, there is a book that would possibly be great for your summer reading. It would put you in a different orbit than any of your classmates, any other diabetic runner, most any runner. Different solar system actually. It is not an easy read, but with your background I am sure you could churn right through it. Something I can recommend if you want to learn some of these things during your school break time.