How Physical Activity Affects Glucose: From Theory to Practice

Physical activity is a powerful non-pharmacological tool for managing diabetes. Its effect can be compared to adding an extra dose of insulin, but with many additional health benefits. However, like any powerful tool, exercise requires understanding physiology. The wrong approach can lead to dangerous hypoglycemia or, conversely, an unexpected rise in blood sugar. Let's understand how to make movement your ally.

The Mechanism: Why Muscles "Eat" Sugar

During physical activity, working muscles consume glucose in two ways:

• Insulin-independent pathway: Muscle contraction activates GLUT-4 glucose transporters directly during exercise, without insulin involvement. This allows lowering blood sugar even with insulin resistance.
• Increased sensitivity: After training, cell sensitivity to insulin remains elevated for several hours to 24–48 hours. This phenomenon is called the "delayed effect" of physical activity.

Two Types of Exercise — Different Effects on Glucose

Not all exercises affect blood sugar the same way. Understanding these differences will help you plan workouts safely.

1. Aerobic Exercise (Cardio)

• Examples: walking, jogging, swimming, cycling, elliptical trainer.
• Effect: Typically lowers glucose levels during and immediately after exercise. This is a predictable and desirable effect for most people with type 2 diabetes.
• Risks: With high insulin levels on board or prolonged training, hypoglycemia may develop.

2. Anaerobic Exercise (Strength and High-Intensity)

• Examples: weightlifting, sprinting, CrossFit, high-intensity interval training (HIIT).
• Effect: May cause a temporary increase in glucose. This occurs due to the release of counter-regulatory hormones (adrenaline, cortisol), which stimulate the liver to release stored glucose to fuel muscles.
• Important: This increase is generally safe and temporary. 1–2 hours after such training, blood sugar often becomes lower than baseline.

The optimal strategy is to combine both types of exercise. For example, warm-up (cardio), then strength training, then cool-down (cardio/stretching).

The "Three Times" Rule: How to Exercise Safely

1. Before Exercise

• Check your glucose level. The ideal range to start exercising is 7–10 mmol/L.
• If blood sugar is below 5 mmol/L — eat 10–15 g of slow carbohydrates (e.g., whole grain bread).
• If blood sugar is above 13–15 mmol/L — ensure no ketone bodies are present. If ketones are present, do not exercise — this can cause ketoacidosis. If no ketones, you can start with light aerobic exercise.

2. During Exercise

• If training lasts longer than 30–40 minutes, especially aerobic, monitor how you feel. Dizziness, weakness, cold sweat are signs of hypoglycemia.
• Keep fast-acting carbohydrates with you (juice, glucose tablets). If you feel hypoglycemia, stop and take 15 g of fast carbohydrates.

3. After Exercise ("Delayed Effect")

• This is the most important and often overlooked aspect. Increased insulin sensitivity lasts up to 48 hours.
• Risk of hypoglycemia may occur not immediately, but 4–12 hours after exercise (e.g., at night).
• After intense training, consider reducing your short-acting insulin dose for the next meal (by 20–50% depending on intensity) and monitor glucose more frequently.

Accurate Monitoring — The Key to Effective Exercise

Physical activity is not a sprint, but a marathon. The most important thing in this marathon is safety. It is impossible to find the ideal exercise regimen without a reliable self-monitoring tool.

Modern glucose meters with FAD-GDH technology provide high measurement accuracy, independent of oxygen fluctuations and the presence of other sugars in the blood. This is especially important for active people, as physical activity itself changes the gas composition of the blood.

Regular glucose measurement before, during (if needed), and after exercise will allow you to create your own map of safe activities. You will learn exactly how your body responds to different types of activity and can use exercise as an effective medicine without side effects.

Remember: Before starting any new exercise program, be sure to consult your endocrinologist.