T1 Diabetes Exercise Math Model

Discussion in 'Health and medical' started by jdumas, Apr 11, 2012.

  1. jdumas

    jdumas New Member

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    I'm in the process of training on a road racer and I have type 1 diabetes that is changing with 25-50% endogenous insulin production after about 26 years post diagnosis. I have an insulin transport model on a handheld for dosing insulin "on the fly" to roll with the punches from life. I have just set up an exercise subsystem for the training effect impact on insulin dosing as well as nocturnal Growth Hormone -> Insulin-like Growth Factor-1 glucose disposal at about 1am-7am in the morning that has no control system in the body to turn it off when hypoglycemic. So an overdose that is active when this IGF-1 growth hormone component kicks in could cause severe hypoglycemia and possibly death from muscle/breathing seizures while sleeping (the so called Dead-in-Bed Syndrome).

    The basic model has an exponential decay for liver and muscle glycogen rebuilding that starts (maximal effect) at the end of the training session. This decay lasts for 2 days but is most severe for the first 13 hours post-exercise. The half-life for this decay is 6.65 hours, so 2 half-lives in 13.3 hours has 25% of maximal glucose uptake for the liver and muscle glycogen rebuilding. The equivalent insulin dosing for the glycogen rebuilding decay would be delivery to interstitial fluid (not subcutaneous or intramuscular or intravenous). But the half-life of this equivalent dose is 6.65 hours in interstitial fluid for a 2 day training effect. Mathematically, the rate constant for this decay is 5/48h or 0.1041667/hour.

    The IGF-1 growth hormone component is a simple 3 equal compartment that represent an IGF-1 plasma binding protein delay, the plasma compartment and the interstitial fluid compartment; respectively. Personal data suggests IGF-1 is equvalent to about 5U of insulin delivered at 1am, with peak time about 2:30am and gone by 7am. This 5U estimate is for a 22 mile training course and seems to scale with distance in my case. But your mileage may vary, of course. I can detail the math later for those interested.

    The consequence of this exercise model for insulin effects suggests a morning training session is better for the T1 diabetic. If the two components: glycogen rebuilding and IGF-1, overlap for maximal effect, the probability of hypoglycemia increases significantly. So I try to train in the morning to distance the session end point far away from the 1am exercise stimulated IGF-1 pulse. In effect, I now use exercise-induced growth hormone in my insulin therapy to normalize glucose.

    Hope this helps other and open to suggestions.

    Jim Dumas
     
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