Effects of Exercise on Glucose Levels in Children With Type 1 Diabetes

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The effects of aerobic exercise on glucose and counterregulatory hormone concentrations in children with type 1 diabetes, by the Diabetes Research in Children Network (DirecNet) Study Group. Diabetes Care 29:20–25, 2006

What is the problem and what is known about it so far?

Exercise is known to be good for children and teens with type 1 diabetes. However, whenever children with type 1 diabetes exercise or take part in other physical activities, such as sports, they run the risk of having a hypoglycemic episode (when blood glucose levels are too low) or, if they snack too much before the activity, a hyperglycemic episode (when blood glucose levels are too high).

Why did the researchers do this particular study?

Exercise plays a big part in the lives of children and teens with type 1 diabetes, but there aren't many standard recommendations on how to manage blood glucose levels during exercise in kids with diabetes. The researchers wanted to study the effects of aerobic exercise on glucose levels in children and adolescents who have type 1 diabetes.

Aerobic exercise is a type of exercise that works the heart and lungs for an extended period of time. Walking, biking, swimming, jogging, dancing, jump-roping, and many other activities are considered aerobic exercise.

Who was studied?

Fifty children and teens who have type 1 diabetes. At the time of the study, the children and teens were between the ages of 10 and 18.

How was the study done?

The kids took part in four different 15-minute walking sessions, with each session separated by 5 minutes. During the exercise sessions, the kids got their heart rates up to 140 beats each minute, which is considered a moderate level of aerobic activity for children and teens. The exercise sessions started around 4:00 in the afternoon. The researchers measured the kids' blood glucose levels before, during, and after the exercise sessions.

The researchers also measured the levels of counter-regulatory hormones in the youths. Counter-regulatory hormones are body chemicals that raise blood glucose levels. The body releases these chemicals when blood glucose levels drop too low and during times of stress.

The researchers compared these measurements with measurements taken on a day when the children and teens did not exercise.

What did the researchers find?

Forty-six of 50 youths completed the full exercise session. For most of them, blood glucose levels dropped about 25%. Fifteen became hypoglycemic (blood glucose levels too low) either during or right after the exercise, but only one had an increase in blood glucose concentrations.

In the group as a whole, exercise made counter-regulatory hormone levels go up.

This study showed that children and teens who exercise at the time of day when after-school activities usually take place (around 4 p.m.) will usually have a 40% drop in their blood glucose levels. About 30% of the youths tested in this study were treated for blood glucose levels that were too low; most of these episodes occurred in children or teens who had a glucose level under 120 mg/dL before the start of the exercise sessions.

The researchers also found that a tablet containing 15 grams of glucose, which is the standard treatment for hypoglycemia in children who have not exercised, is not enough for children who have exercised (or are exercising) and have hypoglycemia; if kids are exercising, they'll need two or three 15-gram glucose tablets.

What were the limitations of the study?

The researchers did not adjust the rate of insulin during exercise. Further studies are needed to determine whether altering insulin doses at the start of exercise can prevent hypoglycemia.

What are the implications of the study?

The type of exercise, how long the exercise is done, and time of day all play roles in how exercise affects glucose levels in youngsters with type 1 diabetes. Because all cases are different, preventing hypoglycemia or hyperglycemia is difficult and more studies need to be done. The researchers of this study, though, show how important it is to check glucose levels before exercising to see if a snack is required to prevent hypoglycemia (the researchers recommend that a child’s glucose level is above 120 mg/dL before exercising). They also show that kids with type 1 who are exercising will require a larger amount of glucose or carbs (30-45 grams) to treat hypoglycemic episodes.

Visit the American Diabetes Association's clinical recommendations on physical activity/exercise and diabetes.

FOR MORE INFORMATION

Nighttime and Exercise-Induced Hypoglycemia

Youth Zone Web site for kids

Guide to Raising a Child With Diabetes, 2nd ed.

487 Really Cool Tips for Kids With Diabetes