From the Guidelines
Elevated glucose levels during extreme exercise are primarily caused by the body's stress response, which triggers the release of stress hormones like adrenaline, noradrenaline, and cortisol, leading to increased glucose release from the liver and reduced insulin sensitivity. This response is a normal physiological adaptation to provide energy for muscles during intense physical activity 1. The stress hormones stimulate the liver to release stored glucose into the bloodstream through a process called glycogenolysis, and also increase gluconeogenesis, creating new glucose from non-carbohydrate sources like amino acids.
Some key factors that contribute to elevated glucose levels during extreme exercise include:
- Intensity and duration of the activity
- Pre-exercise glucose levels
- Individual variability in glycemic response to exercise
- Use of insulin or insulin secretagogues, which can increase the risk of hypoglycemia if not adjusted for exercise
According to the most recent guidelines, intense activities may actually raise blood glucose levels instead of lowering them, especially if pre-exercise glucose levels are elevated 1. It is essential for individuals with diabetes to be educated on checking blood glucose levels before and after exercise and understanding the potential prolonged effects of exercise on glucose levels.
Proper hydration and balanced nutrition before and after extreme exercise can help manage glucose fluctuations more effectively. Additionally, individuals taking insulin or insulin secretagogues may need to adjust their medication doses or carbohydrate consumption to prevent hypoglycemia during and after exercise 1. Overall, understanding the physiological responses to extreme exercise can help individuals with diabetes better manage their glucose levels and improve their overall health outcomes.
From the Research
Causes of Elevated Glucose Levels with Extreme Exercises
- Elevated glucose levels during extreme exercise are caused by an increase in glucose production (GP) and a decrease in glucose utilization (GU) 2
- The marked catecholamine responses to intense exercise are responsible for both the GP increment and the restrained increase of GU 2
- During intense exercise, GP rises seven- to eightfold and GU rises three- to fourfold, leading to an increase in glycemia and a minimal decrease in plasma insulin 2
- The increase in glucose uptake by working skeletal muscle during prolonged exercise is due to an increase in the translocation of insulin and contraction-sensitive glucose transporter-4 (GLUT4) proteins to the plasma membrane 3
- The maintenance of normal blood glucose levels during exercise depends on the coordination and integration of several physiological systems, including the sympathetic nervous system and the endocrine system 3
Role of Hormones in Regulating Glucose Levels
- Insulin and glucagon play a crucial role in regulating hepatic glucose production and gluconeogenesis during exercise 4
- The rise in glucagon is essential for the increase in hepatic glucose production and the increase in gluconeogenesis during prolonged mild intensity exercise 4
- Insulin still exerts a restraining effect on glucagon-stimulated glucose production and gluconeogenesis, thus preventing hyperglycemia 4
- The catecholamine response to intense exercise increases disproportionately, leading to an increase in glucose levels 5
Factors Affecting Glucose Fluxes
- Work intensity affects the mechanisms by which glucose fluxes are regulated, with high-intensity exercise taking on characteristics of the stress response 5
- The increase in glucose utilization by the working muscle would lead to hypoglycemia were it not accompanied by an increase in hepatic glucose production 5
- The response of the liver to exercise appears to be closely controlled by the endocrine system, with glucagon and insulin playing a key role 5