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Activity, Insulin, and Blood Sugar - what happens when you're active?

I've never been given a really good explanation on this topic.

Okay - I know when you eat, Carbs turn to sugar and in order to keep your Blood Glucose down you take insulin so you can turn Carbs into energy.

So then - why would you want to "reduce" or "SUSPEND" your insulin pump basal temporarily during your active period when you go jogging or hiking or cycling or anything active?  Don't you need the insulin to convert sugar to energy in order to be active?

I know all the literature tells you because you will run the risk of going low if you don't.  But it's never explained why.

Or - is it when you are very active, your body processes sugar to energy differently without using insulin?

I never understood this part and since I want to start leisure cycling through my local parks again (like I used to before being diagnosed - not trail biking or mountain biking) and getting back to a somewhat normal lifestyle again - I wanted someone's perspective on it.
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Hi Tony,
I think that the process of moving glucose into our cells (yes, still using insulin) is more efficient when we exercise (I'm about to get on the treadmill after reading this board!).  Thus, all else equal, it takes less insulin to get the job done.  Sugars are taken out of our blood to fuel the working muscles.

I generally turn down my pump by about 20%, leaving 80% of the basal.  Sometimes that's right, sometimes I still get low or have to snakc, other times I'd've been fine leaving it alone.  Mostly, however, 80% is my number.  Given the activity profile of Humalog, I turn down my pump about 30 min before I start exercising and normally turn it back up (assuming I didn't fall too low) once I'm done.

For youngsters who are growing, I wouldn't be surprised if there were other considerations.  I've long ago stopped growing, and this works well for me.  I'm interested to look at that web site reference you were given, too.
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I don't recommend suspending your pump when you exercise. My son really never suspends his pump. Insulin does work more efficiently when you exercise which may result in lower blood sugars.  Also, exercise takes some glucose out of the body to use for energy during and after exercise which also lowers blood sugars.  So instead of suspending, you may want to use a temp basal.  

Many times the sugar goes up right after exercise due to the glucose being released from the muscles.  One might need a temp basal after exercise also.  The only way to know is trial and error as each person is different.  What I recommend is that people exercise w/the pump in the typical mode, no temp, no suspend, for a time or two to see how they respond to the exercise. You need to check of course before, during if duration is greater than an hour, and after for several hours. After I usually say 1 hr, 2-3 hrs, 4-5, etc. as exercise can cause hypo up to 24 hours afterward. Then, a quality decision can be made as to how to handle it.

And once you find a temp basal that works, you may be able to save it in your pump for next time.

Take care.

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Here's a good link:

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