For people with type 2 diabetes, exercise is an imperative companion piece to managing blood sugars. For people with type 1 diabetes, however, it is a more difficult proposition.
According to Marion J. Franz of the International Diabetes Center in Minneapolis, how a type 1’s blood glucose responds to exercise depends on the timing, intensity, duration and type of exercise conducted. Also, the type of insulin used and state of metabolic control prior to the exercise regimen are important factors.
Franz’ observations were published in the December 1998 Canadian Journal of Diabetes Care.
Exercise and Hypoglycemia
Franz points out that “the acute risks of exercise [in people with type 1 diabetes] include both low blood sugar and high blood sugar. In a study of 300 people with type 1 diabetes, low blood sugar usually occurred between six and 15 hours after completion of the exercise. Franz adds that it rarely occurred during or immediately after the exercise.
Exercise and Hyperglycemia
Franz also points out that high blood sugar following exercise can be due to either insulin deficiency or an increase in counterregulatory hormones and excessive glucose release from the person’s liver.
Insulin Adjustments for Exercise
In considering times to exercise, individuals need to consider peak times of insulin action. Franz points out that if Regular insulin is administered before a meal, exercising immediately after eating can control after-meal blood glucose responses. On the other hand, if the faster-acting Humalog is administered before a meal, exercising after a meal could increase the chances of having low blood sugar. Franz recommends exercising two-to-three hours after eating if Humalog is administered.
For some people, blood sugars are at their lowest in the early morning. Franz suggests that exercising early in the morning before a prebreakfast insulin dose appears to be the most convenient way to offset hypoglycemia. If a type 1 wants to exercise later in the day, it is more advisable to increase the time between insulin injection and the onset of exercise. On the other hand, if a type 1 exercises over an extended period of time (i.e., all morning, all afternoon, all day), a greater reduction in the dose of insulin that works during the time of activity may be advisable. One technique that Franz suggests is to reduce insulin by 10 percent when you exercise. If you take 48 units per day, reduce your Regular insulin dose 4.8 units (10 percent). If your exercise activity takes the entire day (i.e., hiking, cross-country skiing) both the Regular and intermediate-acting insulin should be decreased by 10 percent (total of 9.6 units). Also, insulin taken after the all-day activity might be decreased to prevent late-onset hypoglycemia.
Nutrient Adjustments for Exercise
Franz says that if blood sugars are below 100 mg/dl prior to a workout, a type 1 should not exercise without first ingesting a carbohydrate. On the other hand, if blood glucose is greater than 250 mg/dl before exercise, you should check your urine for ketones. If ketones are moderate to large, wait to exercise until blood glucose is better controlled.
One suggestion Franz has is to record blood sugar readings which can be used to determine patterns that develop as a result of exercise. From there, a type 1 can adjust food and/or insulin intake accordingly.
Franz adds that to avoid fatigue, it is imperative for a type 1 to coordinate insulin doses with carbohydrate intake to assure glucose control and liver glycogen stores. Franz says that coordinating insulin doses with carbohydrate intake is essential to assure good glucose control.
“If exercise is done on a regular basis, snacks should be part of the usual meal plan and usual insulin doses should be adjusted,” says Franz.
Water and other fluids are also essential for any exercise regimen, and should be taken for any exercise lasting up to one hour. For exercise lasting longer than one hour, water and extra carbohydrate are needed.
For more information on diabetes and exercise, you can contact the International Diabetic Athletes Association at (800) 898-4322 or [email protected]