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Next Steps for Exercise


As discussed in the Level 1 article "Exercise Affects BG", it can be challenging to adjust for the decrease in blood glucose that we usually see with exercise. The blood-glucose-lowering effect of physical activity is true especially for aerobic exercise: exercise that is longer in duration and mild to moderate in intensity. Aerobic exercise involves endurance, and includes activities such as running or cycling.

When Does Exercise NOT Lower Blood Glucose?

Anaerobic exercise can raise blood sugar

Anaerobic exercise
, on the other hand, is characterized by brief periods of high-intensity activity followed by longer periods of rest or recovery. Anaerobic exercise includes activities such as hockey or sprinting.  Due to the release of adrenaline (a hormone which creates insulin resistance), anaerobic exercise tends to cause a rise in blood glucose.  You may also see this happen when your child is participating in a game versus a practice. Even though she may have experienced a drop in blood glucose while practicing the sport, she could experience an increase in blood glucose while competing in the sport (due to the release of adrenaline).



Decreasing Blood Glucose

An important thing to note is that when the body is recovering from exercise (either aerobic or anaerobic), the muscles will continue to pull glucose from the blood to replenish their stores. Therefore, blood glucose may continue to drop after the exercise is done… for up to 30 hours post-exercise, depending on the kind of exercise that was performed, as well as on individual differences. To further complicate things, the body becomes more sensitive to insulin following exercise, so a smaller amount of insulin is usually needed for basal needs and/or to cover carbs. 

tips from the trenches of type 1 diabetesWhen my son has finished an activity where he has really worked hard (ie. sweating, out of breath, etc.), he will make sure to give himself less insulin with his pump than usual for the next 1-2 meals. If he uses the usual amount, he will go low because his body is using insulin more effectively (known as increased insulin sensitivity). As well, if the activity is later in the day or has lasted the whole day (skiing), he will have a bedtime snack without giving insulin for it to prevent a nighttime low. For suggestions see Level 2/Exercise/After Exercise.  ~Danielle

It is also interesting to note that when a certain activity is performed regularly, the muscle group involved in that activity will adapt by storing more fuel within the affected muscles. As a result, blood glucose will not be affected as much as when that activity was first started.

tips from the trenches of type 1 diabetes
My son will require more extra carbs for a new activity compared to when he has been doing that activity for a while. For example, he requires about 30 extra carbs/hour when we first start our weekly skiing regime compared to needing only 15-20 carbs/hour towards the end of the ski season.

~Danielle 

Blood Glucose Monitoring

Since all kids are different, figuring out how a particular activity affects your individual child can be challenging.recording blood sugar with exercise Blood glucose monitoring is essential for adjusting for exercise with an active child with diabetes; it allows you to notice glucose trends. It’s important to keep good records, especially when the activity is new. We suggest writing down things like the timing, intensity and duration of the activity, as well as what was done to try to keep blood glucose in the target range. It’s important to check blood glucose before, after, and every ½ hour during exercise, paying particular attention to the direction of blood glucose changes. It’s also very important to monitor blood glucose for several hours after intense exercise or exercise lasting longer than 90 minutes, including at bedtime and in the middle of the night. Remember, nighttime lows are very common after a day of strenuous activity. (See Level 2/ Exercise/ After Exercise

Different Strategies for Different Situations

In Level 1: Exercise Affects BG, we talked about the role of extra carbs in preventing and treating exercise-related lows. Expanding on this idea, it is also important to note that your child’s need for extra carbs may vary across activities and situations.

  • Activities that are longer duration/lower intensity (also called aerobic exercise) such as soccer, cycling, and swimming, will create a need for extra carbs before, (possibly) during, and (often) after the activity.
  • Activities that are shorter duration/higher intensity (also called anaerobic exercise) such as weight lifting, hockey, baseball and sprinting, may not require extra carbs prior to starting the activity. Instead, these types of activities tend to produce a rise in blood glucose during the activity with a delayed drop after the activity. A more effective strategy may be to possibly give extra insulin before these activities and give extra carbs after to prevent a delayed low. Talk to your child’s diabetes health care team about how best to put this into practice. 
  • Stress, or the level of competition involved with the activity, can raise blood glucose due to the release of stress hormones. Therefore, in the case of high-risk sports, or during an actual game (vs. a practice), you may need to experiment with giving the bulk of the extra carbs after the activity rather than before as well as possibly giving more insulin prior to. Talk to your child’s diabetes health care team about how best to put this into practice.
  • Injecting insulin (through a syringe, pen, or infusion set) into an area that will be exercised will cause that insulin to be absorbed more quickly due to increased blood flow to the area. (For example, if your child lifts weights to strengthen his upper body when his current infusion set is located on his arm. Or if your child injects the breakfast bolus into her leg using a pen, and eats her breakfast on the way to figure-skating practice.) This can cause low blood glucose even if your child consumes extra carbs. Monitor blood glucose carefully in this case. Or choose a different injection site.
  • Activity is easier to manage if it’s a part of the daily routine (such as dog-walking or running around at recess). Adjustments will still have to be made for sporadic physical activity that is extra to the usual routine.

To Make a Long Story Short…

  • The important thing, regardless of the strategy you choose, is to try to prevent a low by allowing for the body’s increased need for glucose during exercise. 
  • You can do this by giving some extra carbs ahead of time and then throughout the activity as needed; also by reducing the insulin dose prior to, and/or following, physical activity. 
  • The exception to the above guideline is if an activity is likely to raise blood glucose (anaerobic exercise, stressful activities, highly competitive activities). In this case, you will need to experiment with giving extra carbs after the activity as well as possibly increasing the insulin during the activity. Talk to your child’s diabetes health care team about how best to put this into practice.
  • With all exercise, it is crucial to check blood glucose frequently throughout the activity.
  • Do not allow your child to exercise if they have high blood glucose with ketones. Doing so can increase their risk for developing DKA .



References:

Type 1 Diabetes and Aerobic Exercise: Strategies for Optimal Glycemic Control”. Katherine E. Iscoe, BA, Bruce A. Perkins, MD MPH FRCPC, Michael C. Riddell, PhD.

Robertson K, Adolfsson P, Riddell M, Scheiner G, Hanas R.  Exercise in children and adolescents with diabetes. Pediatric Diabetes 2009: 10 (Suppl. 12): 154-168.




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The above information was reviewed for content accuracy by clinical staff of the Alberta Children’s Hospital Diabetes Clinic.

This material has been developed from sources that we believe are accurate, however, as the field of medicine (in particular as it applies to diabetes) is rapidly evolving, the information should not be relied upon, as it is designed for informational purposes only. It should not be used in place of medical advice, instruction and/or treatment. If you have specific questions, please consult your doctor or appropriate health care professional. 

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