Now that I understand the relationship between the liver functions and glucose as you explained. Are you saying your energy pretty much comes from the glucose floating around in your bloodstream and that this whole "storing of carbs." concept is a bit exaggerated?
Think about it this way.
Although BG levels generally remain constant under normal circumstances, there will always be some amount of glucose moving into the cells because cells will always be using some amount of glucose. So, the system is like a bucket with a hole in it. You will always be replacing some the glucose being used in order to keep BGs at a constant level. Depending upon the type of workout you do, as you work out more, you lose glucose faster, so you will have to replace glucose faster to keep levels constant.
Glucose stored in the form of glycogen in the liver and muscles acts like a reserve tank of glucose. As you work out, you rely on those stores to replace the glucose you are losing. Those stores are very important because once that supply of stored glucose is depleted, you BG will drop and you will hit the wall. How fast you deplete those stores depends on how much you have stored and how fast you use it.
When you finish working out, there is a window of time where your liver and muscles will work to store glucose to previous levels at an optimal rate. This is usually within a couple of hours after your workout. Carbs consumed at this time will preferentially be stored as glycogen to rplace lost stores.
What I gathered from this experiment is that I probably should not have taken that 1.5 unit of insulin before my run because I dropped too fast and way too soon. For the most part, I felt pretty good during the run. But I'm starting to think that contrary to what people say about 100-130 being the ideal BG range, I tend to think that it depends on the individual and the level of activity. Quite frankly because I'm so active, I function better when my BG runs kind of high. Is that strange or unusual?
In diabetics, this system is all broken to hell. First, no matter how hard you workout, without insulin, your muscles cannot use glucose. So, even while you are working out, you have to have some insulin working to allow muscles to use glucose. As you found out, if you use too much, your glucose levels drop too fast and outsrip your cellular capacity to convert glycogen to glucose, which depends on a competely different set of hormones than insulin.
So, you have to find a balance between insulin on board, BG levels at the start of your workout, and how hard/long you will be working out.
Most of us do end up starting our workouts at a higher than normal BG. I would say that starting in the 300s is too high and the recommendation is to not even extercise if your levels ar that high. At those levels, you start to worry about diabetic ketosis. If we are working out for an extended pwriod of time, most of us will consume carbs as we work out to maintain our BG levels rather than spike our BGs to extremely high levels at the start.
I'd definitely cut back on the pre-workout insulin dosage if you are falling from 300s to 100s during your workout. I'm like you. It's not just the BG level that affects my workout, it's how fast my BG is dropping. If my BGs are stable, I can workout comfortably in the 60s and even the 50s. If I'm dropping, 70 becomes uncomfortable.
Since you are on MDI, this is a difficult thing to do. On a pump, I just dial down my basal does and adjust my bolus as needed.
You have the right idea though. It's just a matter of finding the balance between starting BG, insulin dose, workout level, and how many carbs to supplement with as you work out.