Exercise and Type 1 Diabetes (T1DM)

Abstract

Physical exercise is firmly incorporated in the management of type 1 diabetes (T1DM), due to multiple recognized beneficial health effects (cardiovascular disease prevention being preeminent). When glycemic values are not excessively low or high at the time of exercise, few absolute contraindications exist; practical guidelines regarding amount, type, and duration of age-appropriate exercise are regularly updated by entities such as the American Diabetes Association and the International Society for Pediatric and Adolescent Diabetes. Practical implementation of exercise regimens, however, may at times be problematic. In the poorly controlled patient, specific structural changes may occur within skeletal muscle fiber, which is considered by some to be a disease-specific myopathy. Further, even in well-controlled patients, several homeostatic mechanisms regulating carbohydrate metabolism often become impaired, causing hypo- or hyperglycemia during and/or after exercise. Some altered responses may be related to inappropriate exogenous insulin administration, but are often also partly caused by the "metabolic memory" of prior glycemic events. In this context, prior hyperglycemia correlates with increased inflammatory and oxidative stress responses, possibly modulating key exercise-associated cardio-protective pathways. Similarly, prior hypoglycemia correlates with impaired glucose counterregulation, resulting in greater likelihood of further hypoglycemia to develop. Additional exercise responses that may be altered in T1DM include growth factor release, which may be especially important in children and adolescents. These multiple alterations in the exercise response should not discourage physical activity in patients with T1DM, but rather should stimulate the quest for the identification of the exercise formats that maximize beneficial health effects.

The time has come to test the beta cell preserving effects of exercise in patients with new onset type 1 diabetes

“…Exercise promotes fitness, reduces insulin requirement and lipids, improves endothelial function and well-being, and reduces insulin resistance, cardiovascular disease and mortality in patients with type 1 diabetes [62]. However, exercise is associated with an increased risk of hypoglycaemia and increased fluctuations of glucose levels that may explain why it does not always improve glycaemic control [63].…”

Glucagon responses to exercise-induced hypoglycaemia are improved by somatostatin receptor type 2 antagonism in a rat model of diabetes

“…Aerobic exercise is generally thought to promote hypoglycaemia in type 1 diabetes because it enhances insulin-independent glucose disposal without promoting the usual reduction in insulin secretion to help augment hepatic glucose production [33]. Rather than drop during exercise, insulin levels tend to rise [14], likely because of enhanced blood flow and insulin absorption [34].…”

“…Rather than drop during exercise, insulin levels tend to rise [14], likely because of enhanced blood flow and insulin absorption [34]. Other factors, such as impaired counterregulatory responses [33] or reduced hepatic glycogen stores [35], might also contribute to increased risk for exercise-induced hypoglycaemia. There may also be impairments in glucagon secretion during exercise [14], particularly in a setting of hypoglycaemia [7].…”

Short-Acting Insulin Reduction Strategies for Continuous Cycle Ergometer Exercises in Patients with Type 1 Diabetes Mellitus

“…Despite this evidence, the fear of hypoglycemia is the strongest barrier when these patients consider physical activity (3). Exercise-induced hypoglycemia occurs if insulin levels are not adequately lowered before starting to exercise, resulting in an elevated risk of a high glucose uptake rate into the tissue (4). Three possible strategies have been identified to prevent exercise-induced hypoglycemia in patients with type 1 diabetes: first, insulin reduction (short-acting insulin (5)(6)(7) or insulin basal rate in pump therapy (8)), second, supplementation with carbohydrates (9) and third, the combination of insulin reduction and carbohydrate ingestion (10).…”