November/December 2020 Issue
Focus on Fitness: Exercise and Type 1 Diabetes
By Jennifer Van Pelt, MA
Vol. 22, No. 9, P. 56
November is National Diabetes Awareness Month. Type 2 diabetes is the most prevalent type, so awareness efforts frequently emphasize it. With much of the focus on preventing type 2 diabetes with lifestyle changes, the public often isn’t aware of type 1 diabetes and its management.
In type 2 diabetes, which is considered a metabolic and endocrine disorder, the body either resists the effects of the insulin it produces or doesn’t produce enough insulin. Those with type 2 diabetes may be able to manage their condition with diet and exercise alone, or they may require medications or insulin.
In type 1 diabetes, the body doesn’t produce insulin. Type 1 diabetes is considered an autoimmune disease because the body’s immune system attacks insulin-producing cells in the pancreas. Those with type 1 diabetes require insulin, but diet and exercise are important to help prevent complications. According to the American Diabetes Association (ADA), type 1 diabetes affects approximately 1.6 million American adults and children.
ADA guidelines for diabetes care provide the following physical activity recommendations for those with type 1 diabetes1:
• Children and adolescents should exercise for 60 minutes or more daily, including moderate- or vigorous-intensity aerobic activities, with vigorous muscle-strengthening and bone-strengthening activities at least three days per week.
• Most adults should exercise—partaking in moderate- to vigorous-intensity aerobic activities—150 minutes or more per week, at least three days per week, with no more than two consecutive days without exercise. Shorter durations (minimum 75 minutes per week) of vigorous-intensity or interval training may be appropriate for younger and more physically fit adults.
• Adults should perform resistance (strength) training two to three sessions per week on nonconsecutive days.
• Flexibility and balance training are recommended, especially for older adults, and should be performed two to three times per week. Types of flexibility and balance exercises should be based on personal preferences; for example, yoga and tai chi are considered flexibility and balance training.
Managing regular exercise is challenging for those with type 1 diabetes due to fluctuations in blood glucose caused by physical activity, and determining appropriate insulin dosing in response to exercise. Exercise management is further complicated in type 1 diabetes due to unpredictable responses to the same type and intensity of exercise, which may be affected by other factors, such as stress/anxiety levels and comorbidities. Research has shown that different exercise activities and intensities, as well as time of day, can affect blood glucose to the extent that hypoglycemia or hyperglycemia occurs, such as in the following ways2:
• Aerobic exercise can lead to decreased blood glucose and thereby a higher risk of hypoglycemia.
• Aerobic activity in the early morning in a fasting state can increase blood glucose.
• Resistance training in the afternoon can decrease blood glucose, but morning resistance training can increase or not affect blood glucose.
• High-intensity, or anaerobic, exercise when performed for a short time can increase blood glucose and is associated with a potentially greater risk of postexercise hyperglycemia.
• Compared with moderate-intensity aerobic exercise, intermittent high-intensity exercise (eg, high-intensity interval training) may protect against exercise-related hypoglycemia.
Hypoglycemia can develop within 45 minutes of beginning aerobic exercise, and risk of hypoglycemia may be higher for at least 24 hours after exercise. With afternoon and evening aerobic exercise, risk of developing hypoglycemia overnight is higher.3
Exercising with type 1 diabetes, therefore, generally requires more monitoring and diligence than with type 2 diabetes. The relatively recent introduction of continuous glucose monitoring (CGM) has resulted in better research regarding the interaction between blood glucose and exercise. In addition, CGM enables those with type 1 diabetes to better manage exercise and blood glucose, which may lead to improved adherence to regular exercise.2,4
The ADA recommends monitoring blood glucose relative to daily activities and diet to prevent extreme fluctuations, and to consider blood glucose levels before exercise, intensity and duration of exercise, and insulin dosing for effective exercise management. Blood glucose should be monitored before, during, and after exercise, and responses should be tracked to identify patterns. Those with type 1 diabetes may require carbohydrate consumption before and/or during an exercise session to maintain blood glucose levels.
Ketone levels also need to be monitored to avoid diabetic ketoacidosis. High blood glucose before exercise may require that exercise be postponed or modified, depending on ketone levels. Vigorous exercise should be avoided if a ketone test is positive, and the cause of elevated ketone levels should be determined. Endurance exercise, such as marathon running and long-distance swimming, can elevate ketones, as can illness, diet, and missed insulin.1,3
In 2017, an international team of diabetes experts published a consensus statement on exercise management for type 1 diabetes. In their statement, they also identified challenges for those with type 1 diabetes. Approximately 60% of those with type 1 diabetes also have overweight or obesity and high cholesterol, and approximately 40% have hypertension; the majority of those with type 1 diabetes don’t exercise regularly.3
Regular exercise is important to reduce cardiovascular morbidity and mortality, as well as reduce diabetes-related complications. Research has demonstrated that individuals with type 1 diabetes who exercised two or more times weekly had better blood glucose measurements, lower BMI, healthier cholesterol levels, less hypertension, and fewer diabetes complications (eg, retinopathy, ketoacidosis, severe hypoglycemic episodes).3
The consensus statement researchers also identified fear of developing hypo- or hyperglycemia and lack of knowledge of appropriate exercise management as barriers to regular exercise for those with type 1 diabetes.3 For clients with type 1 diabetes, the following strategies may be helpful for motivating them to develop and adhere to a regular exercise routine:
• education about different types of exercise and their effects on blood glucose levels;
• assessing risk of exercise-related diabetes complications and comorbidities that may affect exercise ability (eg, arthritis);
• counseling about appropriate exercise activities for the client’s fitness level and interests that address cardiovascular health, strength, and flexibility;
• assisting parents with managing blood glucose monitoring, diet, and exercise for their children and adolescents with type 1 diabetes;
• reviewing appropriate carbohydrate consumption before, during, and after exercise in response to blood glucose levels;
• encouraging preparation to treat potential exercise-induced hypoglycemia by carrying blood glucose monitoring supplies (or wearing a CGM) and carbohydrate snacks or drinks, as well as wearing or carrying diabetes identification; and
• facilitating discussions with the client’s health care providers regarding the need to adjust insulin dosing in response to a regular exercise program.
Advances in diabetes monitoring and exercise tracking technologies and their integration with smartphone apps can help with motivation and overcoming barriers to exercise, such as fear of hypoglycemia. Daily tracking of blood glucose in relation to exercise can identify patterns associated with exercise activities and duration and improve management of exercise responses. Some CGM systems enable “followers” to be added to view real-time glucose measurements and alerts, a capability commonly being used for management of athletes with type 1 diabetes.3,4
— Jennifer Van Pelt, MA, is a certified group fitness instructor and health care researcher in the Lancaster, Pennsylvania, area.
1. American Diabetes Association. Standards of Medical Care in Diabetes — 2020 abridged for primary care providers. Clin Diabetes. 2020;38(1):10-38.
2. Houlder SK, Yardley JE. Continuous glucose monitoring and exercise in type 1 diabetes: past, present and future. Biosensors (Basel). 2018;8(3):73.
3. Riddell MC, Gallen IW, Smart CE, et al. Exercise management in type 1 diabetes: a consensus statement. Lancet Diabetes Endocrinol. 2017;5(5):377-390.
4. Riddell MC, Pooni R, Fontana FY, Scott SN. Diabetes technology and exercise. Endocrinol Metab Clin North Am. 2020;49(1):109-125.