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September 13, 2002

Exercise and Sports

Question from Barrie, Ontario, Canada:

My son is a gifted athlete. If his blood sugars are in the normal range, what should he take before he plays a spirited game of soccer?


There is no easy answer to this question as the blood sugar response to exercise is individual and dependent on a number of factors. These factors include current levels of circulating insulin; insulin therapy type; relation of exercise time to previous insulin, peak insulin action time; as well as type, intensity, and duration of exercise. To learn how a particular sport or activity will affect blood sugar levels, and what to do pro-actively with both food and insulin to prevent highs and lows, your son will need to test blood sugars frequently before, during and after participation. The Diabetic Athlete by Sheri Colberg, Edward Horton is one of my favorite resources in this area, and should provide you with the guidance you are searching for.

As a general rule of thumb, one-half hour of moderate intensity aerobic exercise should require approximately 15-30 grams of carbohydrate to maintain blood sugar levels. Again, this can vary dramatically and should be individualized with blood glucose testing and patterning. With higher intensity or anaerobic “stop/start” types of activities, it is not uncommon to observe a rise in blood sugar as a result of exercise participation.

Since your son is beginning his sports participation with blood sugars in the normal range, you will most likely wish to start with a carbohydrate snack, using the 15-30 gm of carbohydrate for every one-half hour of exercise. Testing in the middle of participation would be a wise idea and assist in determining the blood sugar level’s directional trend and identify the need for further carbohydrate intake.

Congratulations to you for supporting and encouraging your son’s athletic endeavors. Here’s wishing him the best of success in his soccer season!