Thank you for the link, Hilary.
From what I’ve seen so far: I managed a combination of eating 60g of carbs per hour and reducing bolus for another 5g of carbs per hour (tentatively – my math is dodgy there). This is very very close to what they calculated for a 90kg athlete (which wasn’t all that wrong, if I’m generous) as the maximum edible. I will personally aim for 65-70g of carbs per hour for long distance events in the future, but I will try to get more of that from basal reduction and less from food. It’s ridiculous to have to eat that much.
(^ that there is the line I drew. Anything from here on is probably useless).
I’ve bookmarked it and will check it back after the next longer ride to see if it holds up. Might as well use the forums for some napkin math, because I usually work better with my numbers than generalisations.
Recent experiences of mine (been testing since we started this post):
Example 1: Start at a blood glucose of 200mg/dl (11.1mmol/l), reduce basal rate half an hour prior to sports to 30% of normal (reduction by 0,6 I.E./hour) for 1.5 hours (so 0.9 I.E. less than normal in total), eat 36g of carbs 1 hour before sports, using 20% less bolus (in this case: 3.6 I.E. normally are reduced to 2.8 I.E.). Give a bolus to reduce the 200mg/dl (11.1mmol/l) down to 100/5.6 – my designated target. Use 20% less than normal for this due to the following sports (1.6 I.E. instead of 2 I.E.).
After 30 minutes of vigorous cycling (which is not in the list, but we’ll guesstimate later), blood glucose drops to 50mg/dl (or 2.8 mmol/l).
Example 2: Start at a blood glucose of 200mg/dl (11.1mmol/l), reduce basal rate half an hour prior to sports to 20% of normal (reduction by 0.7 I.E./hour) for 1.5 hours (so 1.05 I.E. less than normal in total), eat 36g of carbs 1 hour before sports, using 20% less bolus (in this case: 3.6 I.E. normally are reduced to 2.8 I.E.). Give a bolus to reduce the 200mg/dl (11.1mmol/l) down to 100/5.6 – my designated target. Use 20% less than normal for this due to the following sports (1.6 I.E. instead of 2 I.E.).
After 30 minutes of vigorous cycling (which is not in the list, but we’ll guesstimate later), blood glucose drops to 100mg/dl (or 5.6 mmol/l).
Result 1: Ignore Excarbs limit of 50% [here: http://www.excarbs.com/insulin-injections-pumps-and-exercise/ ] (in my case only – I think it’s a good starting point).
Result 2: 20% seems the way to go for a fed and watered, high starting glucose. Adjustments and meal boluses of 80% are good.
Long distance comparison guess:
I have to guess here, as I don’t have the proper numbers any more. I used a basal rate of 70-75%, and I have to pretend that both Lanthus and Levemir are smooth (otherwise I can’t calculate it). That gives me a reduction of:
Case 1: (4-1=1I.E. per 16 hours for daytime dose of Levemir) -> 0.0625 I.E./hour
Case 2: (12-3=9I.E. per 16 hours for nighttime dose of Levemir) -> 0.5625 I.E./hour
Case 3: (16-4=12I.E. per 24 hours for dose of Lanthus) -> 0.5 I.E./hour
Result 1: No wonder the pump makes things easier. Those doses are off by a factor of 10!
Result 2: 1 I.E. of insulin accounts for 10g of carbs, so if reducing my basal rate by 1 I.E. accounts for 10g of carbs less eaten (that sentence makes my head spin – sorry. I’m a foreigner), then I basically accounted for 5g of carbs per hour with my insulin (no wonder it wasn’t enough on it’s own).
Result 3: The only number I have nailed down is 1000g of carbs over 16.5 hours (which is the total time before DNF on the second attempt minus the two hours of no-food at the beginning). This comes out to 60.6 grams of carbs per hour. Which is very close to what they calculated here: http://www.excarbs.com/adjusting-carbohydrate-for-exercise/ .
That was the number I could squeeze into myself without bolusing by eating as much as I could keep down. It included two rest stops at McDonalds (where I’d usually eat more, but that time barely managed two large fries and a half eaten hamburger plus two cokes at the first stop and two breakfasts plus two cokes at the second), two petrol station with a sandwich and coke each and loads and loads of bananas and cycling type gel foods. I think they are pretty much spot on with “you cannot eat more than 60g of carbs an hour”. Next time I’ll reduce basal rate more, though.