Exercise tips for type 1 diabetes offered by consensus statement

While there are benefits of regular exercise for people with type 1 diabetes, barriers exist that can be managed, according to an up-to-date consensus on exercise management in this population.

The consensus statement, which was published online Jan. 24 by The Lancet Diabetes and Endocrinology, advises physicians about ways to manage people with type 1 diabetes who exercise regularly, including glucose targets for safe and effective exercise and nutritional and insulin dose adjustments to protect against exercise-related glucose excursions.

For all patients, blood glucose monitoring before, during, and after exercise is essential to develop strategies and maintain stable glycemia, the consensus statement said. Patient goals for exercise, such as metabolic control, prevention of complications, fitness, weight loss, or competition and performance, should be considered. Patients should be aware of their starting glucose concentrations and should also have blood glucose monitoring equipment and snacks to treat hypoglycemia. They should also be advised to wear or carry some form of diabetes identification.

Strategies depend upon the intent of the exercise. Exercise for weight loss requires strategies that focus on reducing insulin concentrations during and after exercise, as opposed to consuming more carbohydrates, the statement said. If maximizing exercise performance is the primary goal, then nutritional guidance and a modified insulin plan specific to the sporting activity are needed.

The target blood glucose concentration at the start of exercise should be tailored to the individual. A reasonable starting range for most patients doing aerobic exercise lasting up to an hour is 7 to 10 mmol/L (~126 to 180 mg/dL), according to the consensus statement, because this range balances performance considerations against the risk of hypoglycemia.

Achieving and maintaining circulating glucose concentrations in this range is challenging, the statement continued. Glycemic response to exercise varies and is based on several factors, such as the duration and intensity of exercise, the starting level of glycemia, the individual's aerobic fitness, and the amount of insulin in circulation. Anaerobic exercise and a high-intensity interval training session can be started with a lower starting glucose concentration of about 5 to 7 mmol/L (~90 to 126 mg/dL) because glucose concentrations tend to remain relatively stable and fall to a lesser extent than with continuous aerobic exercise, or rise slightly.

Elevated blood ketones (≥1.5 mmol/L) or urine ketones (≥2+ or 4.0 mmol/L) before exercise should be managed before the start of the session by insulin with carbohydrate intake if needed. Physicians should identify the cause of elevated ketone concentrations, such as illness, diet changes, recent prolonged exercise, or skipping insulin. Prolonged endurance activities such as marathons or diets very low in carbohydrates can elevate blood ketone concentrations, and blood glucose level might not be markedly elevated. Physicians should adopt protocols for ketone monitoring and strategies for what to do when blood or urine ketones are elevated. Blood ketone concentrations of 3.0 mmol/L or more should be managed immediately by a hospital emergency department or physician.

Severe hypoglycemia (blood glucose level ≤2.8 mmol/L [~50 mg/dL]) or a hypoglycemic event requiring assistance from another individual within the previous 24 hours is a contraindication to exercise, because of the substantially increased risk of a more serious episode during exercise, according to the consensus statement. Mild hypoglycemia (blood glucose level 2.9 to 3.9 mmol/L [~50 to 70 mg/dL], with the ability to self-treat) requires that the person consider an increased risk of recurrence. Physicians should stress monitoring, and exercise should be avoided if the setting is particularly unsafe, such as alpine skiing, rock climbing, swimming, or trekking alone.

The consensus statement also included additional recommendations about nutritional management, glycemic management, and emerging technology for exercise management.