Rich Weil, M.Ed., CDE
Managing blood glucose during exercise can be a real challenge. Hypoglycemia occurs often during exercise. This is the greatest risk of exercise for people who have diabetes, especially for those who take insulin. High or low blood glucose can harm your physical performance and mental ability. It is also inconvenient to have to stop your workout, or leave the playing field, to test and treat when necessary. In this article, we will cover the why’s and what-to-do’s of managing blood glucose during exercise.
Understanding Blood Glucose and Your Body
To learn how to manage your blood glucose during exercise you will need a simple physiology lesson. Think muscles. They are the engines in your body that burn calories and make you move. And just like any engine that burns fuel to make it go (such as a car burning gasoline), muscles need fuel too. That fuel is fat and carbohydrate (glucose).
During exercise, the demand for fuel increases and the body responds accordingly.
On the wall of every muscle cell are special receptors, like doors, that allow glucose to pass from the bloodstream to the muscle. These doors do not open unless they are unlocked by insulin. The good news is that exercise has an insulin-like effect, making insulin work better in your body. During bouts of activity, the doors swing open easily, allowing more and more glucose to enter the muscle to be burned up for energy. Of course, the problem is that as you continue to exercise, and glucose continues to leave the blood, you may end up with low blood glucose.
Sometimes blood glucose continues to drop after exercise. That is because the glucose in the muscle that was used at the beginning of exercise needs to be replaced. The muscles, all revved up from exercise, continue to take glucose from the bloodstream to replace what was lost.
Sometimes blood glucose rises with exercise, especially vigorous activity such as weight lifting. This is because the liver pumps out glucose at very high rates during high intensity exercise, and sometimes the supply of glucose is greater than your body needs. The muscles cannot burn the glucose as fast as the liver is producing it.
No one disputes the benefits of exercise, but exercise-induced hypoglycemia is a problem to be reckoned with. I am often asked, “What’s the point of exercising if I have to eat to control my blood glucose every time I work out?” It is a fair question. After all, who wants to gain weight from exercise? The good news is that blood glucose can be managed effectively for exercise.
One way to control your blood glucose during exercise is to test often. You can also adjust your insulin or oral medications, and you can adjust your snacks. Look at the example of blood glucose management during exercise on the side of this article.
Meet The Challenge
There’s no question that managing blood glucose during exercise can be a challenge, but it can be done, and the benefits of exercise – weight control, decreased risk of heart disease, improved mood, and many others – are worth it. We recommend that you check in with your doctor or diabetes educator for assistance, and wish you good luck with exercise!
Richard Weil, M.Ed., CDE, is an exercise physiologist, Certified Diabetes Educator, and a Certified Strength and Conditioning Specialist. He is on staff at The New York Obesity Research Center at St. Luke's-Roosevelt Hospital Center in New York City and is in private practice. He has published dozens of articles on exercise, diabetes, and obesity, is on the editorial board of Diabetes Self-Management magazine, has contributed to the exercise chapters of several books, and speaks locally and nationally about exercise, obesity, diabetes, and health, to health professionals and the general public. He is currently involved in research investigating the effects of exercise on prevention of Type 2 diabetes in teenagers.
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Important note: The content of this article is not intended to be a substitute for professional medical advice, diagnosis or treatment. Do not disregard your doctor's advice or delay in seeking it because of something you have read on this article.