Author: AnneMarie Rousseau, DNP, FNP-BC, APRN, CDCES
Exercise or physical activity is an important element of a healthy lifestyle. It can improve sleep, increase energy, strengthen bones and muscles, and improve heart health. The U.S. Department of Health and Human Services (2018) recommends that all adults complete at least 150 minutes of physical activity each week with no more than two consecutive days of no physical activity. They also recommend resistance exercise 2-3 times per week.
Exercise has an especially important role in diabetes management. It improves insulin sensitivity by helping insulin work more efficiently. This can, however, lead to hypoglycemia (low blood sugar) in people with type 1 diabetes. This can make it difficult and discouraging to engage in regular physical activity. It is important for people with type 1 diabetes to identify strategies to maintain optimal glucose management with exercise.
Many such strategies were identified by Riddell et al. in their 2017 publication in The Lancet: Diabetes & Endocrinology titled, “Exercise management in type 1 diabetes: a consensus statement.”
Aerobic exercise causes blood glucose levels to fall. Insulin concentrations increase during exercise, promoting glucose disposal. Hypoglycemia usually develops within 45 minutes of starting aerobic exercise. To resolve and prevent this issue, insulin needs to be reduced and/or carbohydrate intake needs to be increased. Resistance exercise provides better glucose stability or can cause a rise in glucose. High intensity interval training (HIIT) and resistance exercise can slow hypoglycemia. The risk of hypoglycemia is elevated for at least 24 hours during resistance exercise recovery. Due to these different responses to exercise, it is recommended to engage in resistance exercise before aerobic exercise to help prevent hypoglycemia.
This consensus statement identified exercise goals and targets to help optimize glucose levels during exercise. For aerobic activity, it’s recommended for blood sugars to be between 126-180mg/dL at the start of exercise. For anaerobic and HIIT activity, blood sugars should be between 90-129mg/dL.
Starting blood sugar below target (<90 mg/dL)
- Eat/drink 10-20g of carbs before starting exercise
- Wait until blood glucose is >90mg/dL before starting exercise
- Monitor closely for hypoglycemia
Starting blood sugar near target (90-124mg/dL)
- Eat/drink 10g of carbs before starting aerobic exercise
- Anaerobic and HIIT sessions can be started
Starting blood sugar at target levels (126-180mg/dL)
- Aerobic exercise can be started
- Anaerobic exercise and HIIT sessions can be started, but blood glucose could rise
Starting blood sugar slightly above target (182-270mg/dL)
- Aerobic exercise can be started
- Anaerobic exercise can be started, but blood glucose could rise
Starting blood sugar above target (>270mg/dL)
- If the hyperglycemia is not associated with a recent meal or is otherwise unexplained, check blood ketones.
- If blood ketones are elevated, exercise is contraindicated and recommendations from your healthcare team should be followed.
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Riddell, M. C. et al., (2017). Exercise management in type 1 diabetes: a consensus statement. The Lancet: Diabetes & Endocrinology, 5, 377-390. https://www.thelancet.com/action/showPdf?pii=S2213-8587%2817%2930014-1
U.S. Department of Health and Human Services (2018). Physical Activity Guidelines for Americans, 2nd Edition. https://health.gov/sites/default/files/2019-09/Physical_Activity_Guidelines_2nd_edition.pdf