Exercising Well With Automated Insulin Delivery

Exercise is an important part of a healthy lifestyle, and it would be great if someone could write a perfect rule book for doing it well with diabetes. Unfortunately, everybody is a little different with respect to how their body responds to exercise. That, and every type of exercise will cause different types of glucose responses – sometimes high glucose, sometimes low glucose, and sometimes no clear response at all until hours later. 

Advancements in diabetes technology like automated insulin delivery (AID) systems have made exercise with diabetes easier, helping keep glucose levels stable during and after physical activity. However, each system comes with important differences for managing exercise. 

That’s why together the European Association for the Study of Diabetes (EASD) and the International Society for Pediatric and Adolescent Diabetes (ISPAD) recently published a new position statement that provides specific exercise recommendations for commercially available AID systems and other information to help people with diabetes and their care teams optimize glucose management during physical activity.

“There are challenges related to physical activity that are hard to overcome with conventional therapy. Of course, AID provides benefits – it’s safer, more effective, and the benefits go beyond glycemic outcomes,” said Dr. Klemen Dovč, associate professor at the University Medical Center Ljubljana and one of the authors of the position statement. 

“This is a good starting point, but we need to individualize these recommendations,” Dovč said. “You might start with one recommendation but afterwards, it's trial and error. That’s why it’s important to plan and discuss this with each person.”

Here we share some more tips on exercise using AID from Michael Riddell, co-author of the position statement and a professor at York University in Canada, and Laurel Messer, senior director of medical affairs at Tandem Diabetes Care.

How to use AID for different types of exercise

All AID systems have the ability to decrease or suspend basal insulin delivery for low glucose levels to prevent hypoglycemia. However, studies show that these features are typically not as effective during physical activity as they are at rest since insulin sensitivity is much higher during exercise. In addition, the predictive algorithms used to suspend insulin before going low work well overnight post-exercise but tend not to work so well during exercise.

A more successful feature for exercise management unique to AID systems is the ability to set a higher glucose target, sometimes called a temporary or preset target, before starting physical activity. On Tandem’s Control-IQ system, for example, this is called the “exercise activity” feature (the system targets 140-160 mg/dL vs. 112.5-160 mg/dL). For many people, setting a target somewhere between 150-160 mg/dL seems reasonable for exercise.

For exercise that causes glucose levels to drop (typically prolonged aerobic activities like walking, jogging, and cycling), try setting the AID exercise setting 60 to 90 minutes before the start of the activity. This will cause less insulin to circulate in the body during exercise, making it less likely that glucose levels will drop substantially during the activity. While this may seem like a long time to be in an exercise setting before doing any, evidence from multiple studies supports this strategy. Make sure to cancel these settings as soon as you’re done exercising to allow insulin levels to rise before you eat.

For high-intensity aerobic and anaerobic activities (like interval training, mixed martial arts, weight training, and sprinting) try leaving the AID device in a non-exercise setting first to see what happens to your glucose levels. Chances are you don’t need less insulin when you do these types of activities since adrenaline and other hormones help to boost glucose levels. In cases where glucose levels rise after these activities, AID systems tend to work well on their own in bringing glucose levels back to range. However, if you find yourself developing low blood sugar with these types of activities, you can always try the AID exercise settings about 60 minutes before you start.

What glucose levels to aim for when exercising with AID

Most athletes with diabetes aim for a glucose level that is slightly elevated to help prevent low blood sugar. The glycemic targets for starting (and ending) exercise are generally 125-180 mg/dL, according to one consensus document. A lower starting glucose level works well for very intensive exercise that lasts less than 30 minutes, while a higher pre-exercise glucose level works best for more moderate activities that last longer. Learning where you feel the safest (and strongest) for all the various types of activities you do should be part of your diabetes and exercise journey.

Post-exercise high blood sugar is a common occurrence with more intense or competitive physical activities. AID systems will likely manage these highs effectively; usually, the rise in glucose is only temporary. In some cases, a person may want to give a correction dose of insulin after intense exercise if the high lasts more than half an hour without starting to drop back down. It may be a good idea to reduce the amount of insulin for this correction bolus to reduce the chance of going low later. Cooling the body down through light walking and drinking water may also help bring glucose levels down.

Can you exercise after a meal?

You may need to consider using AID exercise settings differently if you ate just before the start of exercise. This is because eating while using AID will often push insulin levels up a little before exercise starts, which will result in having more insulin on board (in the body) during exercise. 

Try to eat meals three or more hours before the start of any prolonged exercise to ensure that insulin and glucose levels are more stable. If you have to eat, try a low-carb snack so that glucose won’t rise too much before you start exercising. Snacking a little during if needed (20-30 grams of carbohydrates along with some protein) should be fine if the AID exercise setting is on.

To carb or not to carb?

It is common for a person with diabetes to eat carbs immediately prior to exercise in order to keep glucose levels from dropping, though this is not necessarily a good idea with AID. AID systems will likely respond to the sudden rise in glucose levels by giving extra insulin before and during exercise, either by increasing basal rates or delivering an automatic correction dose of insulin (like with Control-IQ and future systems).

To prevent this extra insulin before exercise, it’s probably better not to ingest carbohydrates (in particular, simple carbohydrates or sugar) if glucose levels are not low prior to the activity. Using the AID exercise settings and only eating carbs during physical activity if glucose is trending low are likely better approaches to avoiding lows during exercise. If for performance reasons you need to eat carbohydrates (for example, a half marathon or long bike ride), then the consumption of up to 60 grams per hour in smaller intermittent dosages is what many seasoned athletes typically do even if they are on an AID system. 

How to avoid delayed hypoglycemia after exercise

Glucose levels can dip anytime after exercise has ended. Muscles are more sensitive to insulin after exercise as the body replenishes stored glucose burned during the activity, resulting in lower blood sugar. This dip often occurs about 3-6 hours later (but can happen up to 24 hours after) and may happen when you’re sleeping. 

Using AID in an exercise setting for up to 12 hours after a very prolonged and strenuous exercise session will help prevent this from happening. Using these settings for hours after can also reassure the person that they do not need to eat extra carbs at bedtime to avoid low glucose overnight. This will also help prevent over-snacking, which can potentially cause high glucose levels after exercise or weight gain. For more typical activities that last less than an hour, the AID exercise setting does not need to remain on after exercise is done. 

The universal diabetes secret: trial and error

If you live with diabetes, you might already know the secret to all of diabetes management – trial and error. The tips offered here may provide some new ideas to try to help you exercise well with diabetes. Keep trying new things and see what works best for you. It’s always a good idea to work with a healthcare provider or diabetes educator on personalizing your AID system settings to optimize blood sugar levels and prevent hypoglycemia during exercise.

Learn more helpful strategies for exercising with diabetes here:

• Exercise: Don't Let a Fear of Hypo Stop You
• 4 Exercises To Lower Blood Sugar
• 6 Tips To Fit 'Exercise Snacks' Into Your Day