People with type 1 diabetes have variable responses to exercise. But in general, aerobic exercise causes blood sugar to drop while anaerobic exercise tends to cause blood sugar to rise. Activities that are a mix of both aerobic and anaerobic tend to be associated with better blood sugar balance. Of course the intensity of exercise influences these as well as your overall fitness.
With aerobic exercise blood sugar tends to fall (see figure above).
With anaerobic exercise blood sugar tends to rise.
Mixed aerobic and anaerobic exercise tends to stabilize blood sugar levels.
However responses can vary between individuals and also within a person according to a number of factors including fitness, meal composition and timing and recent blood sugar levels.
*Many sports combine aerobic and anaerobic exercise, for example: soccer, football, squash, etc.
Your goal is to reduce your risk of high and low blood glucose levels.
Also, exercise can lead to hypos during, immediately after, or even during the night or early morning after exercise.