Over the years, I have worked with a growing number of marathon runners with T1D - you all rock! With more people using automated insulin delivery (AID) systems, I would also love to hear more from the running community on how you navigate long runs, training, and race days with your food intake and insulin adjustments.
What typically works for you?? What challenges do you have?? Do you stay in automated mode or switch to manual mode?? How do you fuel for long runs??
Please let me know! We are hoping to do a study on marathon running and T1D - so stay tuned! For now, I’d love to hear more from the T1D runners in the community what your usual strategies are
That’s awesome! I’m not a marathoner, but I really admire the dedication it takes to manage T1D while training. Excited to see the results of your study it’s such an important area that doesn’t get talked about enough!
Background - T1D 20 years, using Tandem X2 with Humalog Insulin
Key factors to success:
Exercise mode is not nearly enough for the intensity of running. I personally have a second profile named “Full Send” that is my marathon settings - it’s basically a 50% reduction across the board with basal, I/C ration, and correction factor. I tend to start this 2-3 hours pre-distance run.
Carbs, carbs, and more carbs. I race aiming for 90g per hour usually in the form of gels (Hammer Gel or Never2nd are my favorites) or gummy type sports energy (Clif ShotBloks). I tend to only “cover” this with insulin if I am running high. I’ll supplement these carbs with sports drink if available at aid stations. I’ll opt for electrolytes in all fluids if I can.
I watch heart rate like a hawk as I can guess rate of glucose usage correlated with heart rate and adjust fueling as needed. HR of 150 means 60g per hour, HR of 170 likely means more like 90g per HR.
Pre-race I try to eat 3 hours before and sip on sports drink leading up to the race so I’ve got minimal insulin on board at the start and no gut issues.
A race vest or belt is great to carry all the food and supplies needed as well. I like Raide Research for belt and Salomon for vests.
Pipedream: Determine average glucose disposal rate with %VO2max and % maxHR so I can add it all to my Garmin for race day and training. It would be awesome to understand from a fueling (and reaction timing) requirements perspective.
Hi Mike - I like your thoughtfulness. I haven’t seen a lot of people controlling fueling based on HR targets but that can be a good measure of intensity. Just a couple follow up questions - with your “full send” profile are you keeping CIQ on? do you ever try turning it off? do you still use exercise mode on top of this? what is your personal goal glucose range during exercise? thanks - Joe Henske (working with Dessi on study of marathon runners)
I do keep CIQ on as I want it to suspend insulin if needed. I have played around with exercise mode on and off and find off is a better option as I can set my target higher (190 vs 160). I wish exercise mode eliminated auto bolus as that tends to drive me low. Personal goal glucose is 140-180 but anything between 100-200 is good enough for me. Generally having a higher target BG seems to trick CIQ into a better profile than if I were to set it at my true goal. 190 generally keeps me at 140 with fueling although there is always variation.
I’m glad you have found something that works well for you. You might want to take another look at how this algorithm does the calculations as well. According to the user guide, when you are in control IQ mode, no matter what you set your glucose “target”, CIQ correction boluses will always target a glucose of 110mg/dL. (in fact this is one reason why exercise can be challenging with CIQ autoboluses because not only are they given as aggressively as when you are not exercising, but they still do not target 140 or 160 but 110). The basal algorithm will target 112.5-160 or 140-160 depending whether or not you are in regular or exercise mode. The impact of adjusting your target higher would only work when control IQ is off and you are giving manual corrections.
Ah awesome, I did not know that. Exercise mode it is. I think likely with the decreased I/C ratio and correction factor, maybe the boluses were not super impactful even if correcting to 110. Thanks for that, you learn a new thing everyday!
