Regular exercise has extensive, science-backed benefits on your metabolic health. Exercise elicits structural, functional, and metabolic adaptations to the body that improve heart health, insulin sensitivity, and glucose (blood sugar) control. Routine physical activity also promotes the efficient use of fuel in the muscle, decreases inflammation, and helps manage blood fat levels. (1)
Since exercise directly improves metabolic health, including improving glucose control, you’d probably expect that your glucose levels would be lower during physical activity. However, certain types of exercise can actually increase glucose temporarily. This short-term rise is completely normal and not a cause for concern.
In this article, we’ll explain what happens metabolically in your body during exercise, why it’s normal for your glucose levels to change, and which exercises can cause a temporary spike in glucose. Let’s dive in.
Glucose levels during exercise
It’s normal for your glucose levels to change during exercise. Muscle contractions use glucose for energy, and exercising muscles can take up and use glucose without the need for insulin.
When you start exercising, hormone levels typically increase in the blood, triggering the release of glucose into the blood stream for available use by the muscles. The type and intensity of the exercise will determine the net effect on glucose, in addition to if you consume carbohydrates before or during exercise.
Your individual fitness level can also play a role in how your glucose levels change during exercise. If you’re newer to exercising, almost any movement that gets your heart rate up may raise glucose. This is because exercise creates stress (the good kind) which temporarily raises stress hormones like cortisol, and muscle’s main fuel source: glucose.
As your fitness level improves or if you have years of training experience under your belt, you’ll see glucose rise with higher intensity exercise, such as high-intensity interval training, a hard effort run, or heavy weightlifting. However, not all exercise will spike glucose. Lower intensity exercise, such as walking or hatha style yoga, can actually lower glucose or flatten a glucose spike.
Will I experience glucose spikes during both low-intensity and high-intensity exercise?
Walking and other low- to moderate-intensity exercise that you can do while carrying on a conversation are more likely to lower blood glucose levels. Think: a leisurely bike ride, rowing at a slow pace, or using an elliptical machine.
Relative to higher intensity exercise, low and moderate intensity types of exercises don’t have as high of an energy demand but do help your muscles absorb more glucose, which is why we recommend walking after a meal.
During higher-intensity workouts, such as HIIT, heavy weightlifting, sprints, or competitive sports, your body requires more fuel and uses glucose as the fastest source of energy. Stress hormones including adrenaline are activated and stimulate your liver to release glucose.
This increase in blood glucose may last for an hour or so after exercise. It will eventually return to normal levels with the help of insulin working to lower blood glucose levels and restore glycogen in muscles.
Glucose levels after exercise
What is the science behind your increased glucose levels after hard activity? After exercise, the body is still working hard to restore normal metabolic function. During this time, your body continues to use glucose as a source of energy, and muscles continue to be more sensitive to insulin. (3) This is commonly called the afterburn effect and is scientifically known as oxygen debt.
You may then experience overall lower glucose levels in the 24-72 hours after your workout as your body remains more sensitive to insulin. This is why regular exercise can lower your fasting blood sugar level, a measure of long-term glucose control and metabolic health. (5)
Tips: improving your glucose levels with exercise
- How can exercise/movement improve my glucose?
The UK Chief Medical Officer report recommends at least 150 minutes of moderate-intensity activity, 75 minutes of vigorous activity, or a mixture of both each week. It also recommends muscle-strengthening activities two days per week and to reduce extended periods of sitting. (4) Following this guidance can improve your glucose by increasing insulin sensitivity and building and maintaining muscle, which is the primary user of glucose. - Does it matter what time of day I exercise?
Whatever time you can fit in exercise is the best time. While some research shows afternoon or evening exercise may be more effective than morning exercise to improve glucose control, other studies have found that morning training could provide additional benefits compared with evening exercise as it relates to changes in burning calories and appetite regulation. (6) - Does it matter whether I exercise before or after eating?
Again, whatever time you can fit in exercise is the best time. Incorporating walking soon after meals will promote steady glucose. If you have a hard workout planned, you may need a little more time to digest food before you get your heart rate up. - Is there anything I can use to measure my glucose levels?
Continuous glucose monitors (CGM) like the Lingo biosensor provide real-time glucose insights so you can see how different types of exercise impact your glucose. Lingo will help you understand why it’s still beneficial when your glucose elevates during certain activities and coach you to set healthy habits around exercise.
For active adults and competitive athletes, CGMs offer unique insights to optimise their fuel tank prior to exercise, ensure steady energy levels during exercise, and guide proper refuelling afterwards.
A final note from Lingo
Low- to moderate-intensity exercise (e.g. walking) lowers glucose, and higher intensity exercise (e.g. HIIT) temporarily raises glucose. All exercise is beneficial for metabolic health because it improves insulin sensitivity and glucose regulation over the long term. Furthermore, exercise reduces stress, which has a positive impact on glucose.
Overall, people who exercise regularly have a higher quality of life and better health outcomes. (7)