" Aerobic activity is beneficial in several ways. Exercise strengthens your cardiovascular system and improves your circulation, which means your body can deliver more blood to your brain when it’s working. Because the brain’s demand for oxygen and sugar rises when you’re concentrating hard, this can make the difference between grasping that insight or feeling like it’s just out of reach. A firing neuron uses as much energy as a leg muscle cell during a marathon. Further, sustained aerobic exercise stimulates the body to generate more small blood vessels in the brain, and a better-developed cerebral vasculature can deliver blood to the brain faster and more effectively. A 2012 study found that episodic memory improves as maximal oxygen capacity increases. (Conversely, comparative studies of adults who do and don’t exercise find that couch potatoes have lower scores on tests of executive function and processing speed and in middle age have faster rates of brain "

― Alex Soojung-Kim Pang , Rest: Why You Get More Done When You Work Less