In endurance athletes, the intensity of exercise—measured relative to their individual performance threshold—is the main factor that causes glucose levels in the tissue fluid to rise during training, regardless of how many carbohydrates they eat.

When athletes consume carbohydrates before running for a long time, higher rates of carbohydrate use and insulin release are linked to less decline in the brain's ability to fully activate muscles during the run.

Doing light, steady exercise like walking or slow cycling doesn’t seem to change blood sugar levels much in healthy adults who don’t usually exercise.

After a hard, short workout, your body releases more sugar and insulin into the blood, which helps your muscles refill their energy faster.