Exercise and Insulin-Dependent Diabetes

October 11, 2019
Diasome.comDiasome BlogExercise and Insulin-Dependent Diabetes
Christel Oerum
Christel is a Los Angeles based speaker, writer, diabetes coach and diabetes advocate. She has been living with type 1 diabetes since 1997 and at an early stage decided that it wasn’t going to slow her down. Her motto is “There is Nothing You Can’t do With Diabetes”. She writes about how to be Fit With Diabetes on DiabetesStrong.com. She also coaches people with diabetes from across the globe, online and in person, and supports them in meeting their health and fitness goals. Disclaimer: The individual medical decisions included in this blog are not intended to substitute for professional medical advice, treatment and/or diagnosis.
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Exercise and Insulin-Dependent Diabetes

There is no doubt that exercise is good for everybody, and as people living with diabetes, we are encouraged to move daily. The only problem with that advice is that insulin is a temperamental hormone, and how effective it is can be greatly impacted by exercise, severely increasing the risk of hypo- or hyperglycemia.

Most rapid-acting insulins last 3-5 hours in the body and if you want to exercise within that timeframe, you need to be extra careful to not end up in a dangerous situation. It sounds simple enough, but in reality, it can be a complex equation to handle, and many people living with diabetes have never properly been taught how to go about it.

When we talk about exercise, there are basically two forms -aerobic and anaerobic exercise. Each form has its own unique challenges when it comes to diabetes management.

Aerobic Exercise & Diabetes

Aerobic exercise is the type of exercise where the heart rate comes up and stays fairly stable throughout the duration of the workout.Some examples are brisk walking, jogging, swimming, and dancing.

When we engage in aerobic exercise, we’ll typically see our blood sugar decrease during exercise. We may even increase our insulin sensitivity (how effectively the body utilizes the insulin) for hours after we're done. That means an increased risk of hypoglycemia.

When someone without diabetes performs anaerobic exercise, their body will automatically turn off the insulin production to prevent hypoglycemia, but for us people living with insulin-dependent diabetes, we have to reduce our insulin ourselves. Remember, insulin lasts 3-5 hours, so any rapid-acting insulin (for people managing with an insulin pump that means basal insulin as well) injected within that timeframe can potentially be impacted by exercise.

This means that in order to reduce the risk of hypoglycemia, most people will have to reduce the amount of insulin they inject the hours before their workout. The key, and where it gets complicated, is to understand how much to reduce your insulin, without experiencing hypoglycemia instead.

In my opinion, there is only one good way of learning how much to reduce, and that’s through structured trial and error. For that’s the thing with diabetes, it’s a little different for everyone.

Anaerobic Exercise & Diabetes

Anaerobic exercise is characterized by the heart rate fluctuating between being extremely elevated and periods of rest. Good examples of anaerobic exercise are HIIT (high-intensity interval training), resistance training, sprints, CrossFit, and Bootcamp types of training, as well as some team sports.

Anaerobic exercise can impact blood sugars dramatically different than aerobic activity because it often increases your blood sugar rather than decreasing it. Some people will even see that their blood sugar shoots up drastically after as little as 10-20minutes of anaerobic exercise.

Although your insulin sensitivity may increase significantly during and after doing anaerobic exercise, your body will typically be releasing large amounts of glucose to fuel the activity, which can lead to high blood sugars.

The key here, and this is also tricky, is to increase the rapid-acting insulin just enough to prevent blood sugar spikes but not so much that it leads to hypoglycemia.

Another consideration is that after the anaerobic exercise is completed, the increased insulin sensitivity can continue for several hours, again increasing the risk of hypoglycemia after the workout - especially if additional insulin has been injected to prevent going high during the workout.

In the same way as for aerobic exercise, I believe that the best way of learning how to adjust the insulin amount to the activity is through structured trial and error. But it has to be done in a safe manner.

The way I approach it is that I’d rather run a little high the first few times I try out a new type of exercise before I start to significantly adjust my insulin. That can be done by adjusting my insulin for aerobic activity or eating more carbs.

And always, always take detailed notes so that you can learn quickly and adjust your insulin to limit those exercise high or lows.    

The views and opinions expressed in this article are those of the authors and do not reflect the official policy or position of Diasome.

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