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How exercise affect blood glucose?

Type 1 diabetics are always told that exercise can help them control blood glucose levels, but what most healthcare practitioners fail to explain is how to manage blood glucose while performing different types of activity. Having good glucose levels during your workouts will massively improve your mental wellbeing, confidence, and overall happiness. To understand how to manage blood glucose (BG) during workouts, we need to look at what happens in our bodies during different types of workouts: the physiological processes that can affect our BGs. For diabetic purposes, exercise can be categorised into 3 types:

Cardiovascular exercise: Examples are running, walking, cycling, swimming, or yoga. Any movement that is repetitive and non-explosive. Usually done at a lower heart rate.
Resistance training: For example, heavyweight training, variations of CrossFit, and similar training with heavy loads. Done at a higher heart rate.
HIIT training: This would be any form of explosive movement or sprint training: sprint running, HIIT classes, boxing classes, most spin studio classes. This would be exercise close to maximum heart rate.

During cardiovascular training, our body uses up the glycogen stored in our muscles and uses glucose to replenish them for more energy. Our blood glucose will consequently start dropping in 15 minutes after the start of the session. To prevent a low and having to pause the session, there are several options you can take:

– Exercise shortly after a meal with a reduced bolus. About a 20% bolus reduction should be enough, but you may need more or less.
– Eat 15-20g of quick-acting carbs 20 min before your workout to keep levels up and provide the glucose to muscle for energy regeneration.
– If on pump, reduce basal 2 hours before your workout, so that the insulin level in your body has time to adjust. Don’t forget to turn the basal back on before the end of your workout to avoid spiking after.

If your workout is up to 1 hour long, the above adjustments should be enough to keep you from dropping low. If it is over an hour, you may need to consume more carbohydrates during the workout (around or after the 1h mark) to keep your levels stable. In anaerobic training (resistance and HIIT), “fight or flight” hormones such as adrenaline, cortisol and other stress hormones are released as a response, which causes the liver to release glucose into the bloodstream, which then makes our blood sugars rise. To prevent this from happening there is only one thing we need to do: have more insulin. This can be achieved in several ways:

– Eat a meal/ snack with your normal bolus, so that you have active insulin on board. The improved insulin sensitivity and the liver damp should balance each other out and give you a straight line of BGs.
– Simply inject before your workout, but you would need a smaller correction dose than you would need to correct the same number in a non-active state. The dose you need is individual, and you can figure it out by monitoring your workouts for several sessions and identifying a pattern.

We are all unique, but physiological reactions of the body are similar. Categorise your activity correctly: doing light weights will count as cardio and not resistance training. Make sure to always check your blood sugars, identify patterns, and make the decisions that are right for your body, no matter if it is different from what others are doing.

This article was written by Daria from T1Level.


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