Diabetes: Exercise increases insulin sensitivity, stimulation of brain and memory and cell growth
For the past two summers I have driven to Ithaca, New York, to take a five-day course at Cornell Adult University. Ithaca is at its best during the summer when the fog and weather do not interfere with the beautiful campus. Last year, I took a Jane Austen literature course. This year, due to the absence of British literature offerings, I took a seminar on "Memory and the Brain." It was taught by a PhD psychologist directed a group of 18 adults through the mazes of memory. Although his subjects were indeed rats (cute ones, actually), much of the material had direct application to humans because both our species share mammalian characteristics.
We spent five days learning about brain anatomy and different types of memory. Among the most striking things we learned was that exercise enables the growth and regeneration (neurogenesis) of certain neurons in the brain. Naturally, I began to wonder if exercise would also play a role in the development of new pancreatic islet cells. (As you know, the islet cells do regenerate, but are continually destroyed by the autoimmune process). Exercise also encourages the formation of new blood vessels (arteriogenesis) and therefore, in theory, probably enables growth and regeneration of other cells in the body as well. The key message is that exercise promotes many beneficial properties for human cells. Having said that, why does the mere mention of strenuous exercise provoke anxiety in many caregivers of children and teens with type 1 diabetes? With the fear of hypoglycemia, many children and teens are unable to participate in overnight camps, sports, and school excursions.
As the last few weeks of the summer vacation comes to a close, I would like to provide some tips to help with hypoglycemia avoidance. The goal is to have diabetes management fit into your activities rather than having your activities arranged around diabetes. It is so much easier said than actually done!
1. All exercise is not equal. Different activities may cause different patterns of blood sugars. Some activities that increase the stress hormones of epinephrine, etc., may actually cause blood sugar to increase at the onset of activity. This response may occur in association with the actual competitive event (football, basketball game, etc.). However, practice sessions may not provoke hyperglycemia initially and hypoglycemia may ensue up to 24 hours later. Therefore, it is important to determine how each individual reacts to different forms of exercise (practice vs. competitive event).
2. I would also suggest a "starting" exercise blood sugar goal, somewhere between 150-250 mg/dl depending on your unique response to exercise. It is important to consult with your diabetes team to determine your ideal pre-exercise blood sugar to avoid both initial hyperglycemia and hypoglycemia.
3. The type of insulin regimen may determine the method utilized to avoid hypoglycemia.
Conventional split mixed insulin with NPH/regular or analog (two or three shots/day):
1. Consider an extra snack before exercising - especially in the afternoon.
2. Consider decreasing the fast or rapid acting insulin before exercising if after breakfast or dinner.
3. Consider decreasing bedtime long acting insulin (NPH or Levemir) to avoid post-exercise induced hypoglycemia.
Basal/bolus: multiple injections:
1. Consider decreasing rapid acting insulin (if eating) before an activity.
2. Consider having a snack with less insulin based on the insulin/carbohydrate ratio and correction factor.
3. Consider giving a small snack before the activity and bolusing for half the amount to avoid the hyperglycemia that may accompany the activity. Giving a snack with a small amount of insulin will help to prevent the liver from breaking down stored glucose (glycogen) into glucose that will be released into circulation.
4. Consider decreasing the bedtime analog basal insulin such as Levemir (which may last 12-16 hours). Note that it may be problematic to decrease Lantus due to the fact that higher blood sugars may result secondary to its 24-hour profile.
5. Check blood sugars frequently and use only the amount of carbohydrates necessary to increase the blood sugar an appropriate amount.
For example, if the blood sugar is 50 mg/dl, insulin/carbohydrate ratio is 15 and the correction factor (insulin sensitivity factor) is 50, the relationship is such that 15 grams of carbs will increase the blood sugar 50 mg/dl. So, eat 30 grams of carbs to increase blood sugar 100 mg/dl resulting in an @ blood sugar of 150 mg/dl. DO NOT eat 90 grams of carbs to increase the blood sugar by 300 mg/dl!
Insulin Pump Therapy:
1. May apply same principles as basal/bolus therapy with multiple injections
2. Consider removing the pump; but would suggest only for one hour at a time and then reconnect as necessary depending on blood sugar or if snacking.
3. Consider using lower temporary basal rates as necessary to avoid immediate hypoglycemia and post exercise induced hypoglycemia.
4. Consider use of Lantus or Levemir as basal insulin and connecting to the pump to bolus as necessary for meals or correction if you intend to be active all day while on vacation or swimming. In this way, one can avoid some of the connection/reconnection conundrums. (Levemir and Lantus doses would initially approximate the total daily basal rate, one would then decrease as necessary depending on blood sugars.)
Our diabetes team commonly provides these tips throughout our clinic visits. There are many books that can give more specific advice. Check out this site (especially Anna's post: "Different Exercise, Different Energy System, Different Blood Sugars," the American Diabetes Association, and the Children with Diabetes web sites. Likewise, exercise physiologists may also be an excellent source of information especially for specific sports.
The most important message to remember is that exercise enables many positive events to occur, such as increased insulin sensitivity, stimulation of brain and memory, cell growth, improved healing and stress reduction. Therefore, it is incumbent for caregivers of children and teens with type 1 or 2 diabetes to help us to help you develop proactive strategies to avoid hypoglycemia and enable your child to participate in all activities.