Muscles hold enough energy for a 30-second burst of activity. After that, they depend on increased blood supply to deliver oxygen and blood sugar to manufacture more energy. Your body burns the sugar in your blood, and then calls for your liver to supply stored glucose to keep up with energy demands. This causes fluctuations in your blood sugar when you exercise.
Blood Supply
As you warm up, your muscles start to call for supplies to manufacture energy. Glucose carried in your blood and delivered to the muscles is an energy supply. This helps balance high blood sugar and provide fuel at the same time. As blood flow to your muscles increases, the glucose supplies increase as well. Your muscle cells send signals to start burning glucose, and more of it is delivered to the cells. This lowers your blood sugar levels.
Stored Sugars
Sugars from the foods you eat are stored in your liver. When your body requires more sugar than is available in your blood, it starts to convert stored sugars to a usable form called glycogen. Blood sugar levels in your blood increase as glycogen releases into your bloodstream. When glycogen is the fuel for your muscles, your blood sugar fluctuates.
Elevated Blood Sugar
If your blood sugar is high when you begin to exercise, it can climb higher. This is because your body does not recognize the glucose in your blood, and calls for your liver to release more glycogen. The activity of insulin in your body is low, and it is not regulating the sugar. If your blood sugar is high before exercise, you should wait until it is within normal range before you exercise, according to Johns Hopkins Medicine.
Post Exercise Blood Sugar
Your body uses all available and stored sugars when you exercise. It is possible to burn off all the glycogen. When this happens, you feel dizzy, your vision gets poor and you become unconscious. This is because your brain requires a certain level of glucose to work. If the level becomes too low, you lose consciousness. When your exercise session is complete, your blood sugar levels stay low as the stores are rebuilt in your liver and muscles.
