During a 10k run, you’ll need more than strong legs to cross the finish line. Your brain works just as hard and, like your muscles, it needs constant energy in order to keep going. One source of energy for your brain is the glucose—or sugar—in your bloodstream. Scientists once thought this was the only food enjoyed by your brain’s neurons. They now know that neurons also rely upon energy provided by support cells called astrocytes, which increase with regular exercise. These cells contain glycogen—like that stored in the liver—that acts as an energy reserve. When the glucose in the blood is depleted, astrocytes break down the glycogen in order to feed the neurons. In one study by Japanese researchers, they found that prolonged exercise by rats drastically decreased the energy stores in the areas of the brain involved in thinking, memory and moving. These contain the neurons that would be the most active as you navigate a 10k course. Howeer, in a second study, the researchers showed what happens after the rat’s big race. When animals were allowed to eat after exercise, the glycogen stores increased past their pre-exercise levels, what is called “supercompensation.” For rats that exercised only one time, this effect lasted only 24 hours. After four weeks of moderate exercise, though, the glycogen levels remained at a higher level than that seen in sedentary animals. Exercise had reset the baseline level of the energy stores, basically prepping the brain for increased activity during exercise. Even more, the researchers found that rats who ate carbohydrates right after exercise had higher levels of supercompensation. While this research was done in animals, it does hint at what’s going on in your brain as you hit the mental wall toward the end of your run. So keep your body and brain fueled, and try eating some healthy carbs after you cross the finish line.