Depending on your blood glucose concentration, or blood sugar, prior to exercise, exercise can increase or decrease it. You should only exercise while your blood glucose concentration is in a normal and acceptable range for activity. However, if done correctly, regular physical activity can be effective in the long-term management of your diabetes and blood glucose concentration.
Immediate Response to Exercise
At the onset of exercise, two things happen. First, your body inhibits the release of insulin. This can affect your blood glucose concentration because insulin is the mechanism your body uses to move glucose from the blood and into your cells. Second, the body increases glucose output from the liver into the bloodstream for use by your muscles. Both of these responses cause a slight increase in blood glucose concentration at the onset of exercise.
Long-Term Response
The increase in blood glucose concentration at the start of exercise is short-lived. Your muscles are able to take in glucose through a noninsulin mediated method. The contractions of your muscles stimulate glucose transporters to the outside your muscle cells. These transporters take in glucose from the blood to produce energy. This as well as a reduction in insulin ensures that the cells that need glucose the most receive it.
Hyperglycemia
If you begin exercising at a dangerously high blood glucose concentration, exercise may make it even higher. If your blood glucose concentration measures 240 mg/dL or higher, check your urine for ketones. If ketones are present, do not exercise. This means there is a problem with your body's ability to move glucose from the blood and into cells. Upon exercise, your body will continue to release glucose into the bloodstream because it does not know how high your blood glucose concentration is, only that your cells are not receiving it. This can cause major problems including ketoacidosis, which can result in a coma.
Hypoglycemia
Exercising with too low of a blood glucose concentration can be dangerous as well. The non-insulin-mediated glucose transport into your cells may make it even lower. Never exercise if your blood glucose concentration is less than 100 mg/dL. If it is, eat a carbohydrate-rich snack and then retest until it reaches greater than 100 mg/dL. Exercising with too low of a blood glucose concentration can lead to hypoglycemia. This can be dangerous and, if left untreated, can lead to a seizure, coma or death.
Recommendations
Regular exercise can be effective in the long-term management of blood glucose concentration, when done properly. Participate in aerobic exercise four days per week for 20 to 60 minutes at a light to moderate intensity, recommends the American College of Sports Medicine. Include resistance training of a light intensity including working the large muscle groups for 10 to 15 repetitions. Only exercise if your blood glucose concentration is greater than 100 mg/dL but less than 250 mg/dL. Check with your doctor before starting an exercise program.
References
- "Exercise Physiology: Human Bioenergetics and Its Applications"; George A. Brooks, et al.; 2005
- American Diabetes Association: Hyperglycemia
- "ACSM's Guidelines For Exercise Testing and Prescription"; Mitchell H. Whaley, PhD, et al.; 2006
- MayoClinic.com; Hypoglycemia: Complications; 2010
