I am not sure if I understand your last question about reducing the amount if insulin needed over time.
I am a Diabetic Lifestyle Coach with a PhD degree in biochemical physiology, and have T1D for 20 years, so I will try to explain as best I can. Just for your understanding, I manage my blood glucose through a healthy and very active lifestyle (I ride 400-500 miles per week by bicycle), and I know what you are talking about when it comes to blood glucose spikes during a high-intensity workout.
Dennis J Dacey (he happens to have the same first name as I do!), was pretty accurate with his explanation. And so was Linda. Let me give you a little bit of scientific insight:
When we do low-intensity exercise, we hardly use any glycogen (which is a large molecule made out of thousands of glucose molecules); our bodies prefer to use fat and save the precious glycogen for “emergency” activities.
Both your muscles and your liver can store glycogen. When you do a high-intensity workout, the fuel that is readily available for your muscles is - of course - the glycogen that is stored in your muscles. But as these stores run out, your muscles start to absorb circulating glucose from your blood stream. This lowers your blood glucose and that gets noticed by your liver, which then releases glycogen from its own stores to regain the balance in your blood.
If you immediately jump into a high-intensity workout, your body also produces a lot of adrenaline, which triggers your liver to release a burst of glycogen into the blood, even before your muscles start to run low. If your liver releases faster and more of this complex glucose than you can burn, your blood glucose will spike. And since you’re T1D (like me!), you don’t produce any insulin to get that glucose back to where it came from. This means that you will have to inject insulin to get that circulating glucose back into your liver and muscles (or you have to keep working out hard until the glucose is burned up to fuel your exercise).
Just be careful not to over-dose with the insulin, as your body is also hyper-sensitive to this hormone when you are so physically active.
Hope this helps.
[edited by moderator]