The Dangers of "The Boomerang Effect"

On Saturday, I ran 11 miles and felt good--both in terms of results as well as in managing my blood sugars. My pre-run reading was 137, post-run 124. I set my basal rate at 30% for 2 hours for the length of the run, running the distance in a comfortably slow aerobic heart-rate speed of 10 minutes per mile (1:50:03). But two days later, I had low blood sugar readings almost all day long, particularly later in the afternoon. At 5PM my reading was 56, so I quickly downed a Glutose tube but still felt "out of it." I was able to walk to our office vending machine to purchase a regular Coke, drank half of it, and checked myself 15 minutes later. The reading was still only 58. I finished the rest of the Coke (39 grams of total carbs!) and my blood sugar eventually got to 72. I remember my endocrinologist telling me that there is a phenomenon known as "the boomerang effect." The type-1 diabetic body can actually become hyper-efficient at utilizing insulin post long-runs, and this can continue for 24 to 48 hours. What this also means is that one should closely monitor one's blood sugars and even consider cutting back one's basal rate (I did not) for some period of time after prolonged and intensive physical activity. I had forgotten about this potential effect, so the next time I run 12 miles (in two weeks) I will lower my basal rate slightly for 1-2 days post run and reduce the risks of low blood sugars. CHECK WITH YOUR DOCTOR before making any changes in your insulin regime or increasing your exercise program. Happy running, now that spring finally looks to be on its way in Virginia.