The principles in the book are listed as “Brain Rules.” The first rule is, “Exercise boosts brain power.”
The brain, as an organ, requires great amounts of brain food. It also generates lots of toxic waste. Physical activity is an helps in feeding the brain and eliminating waste.
“When you exercise, you increase the blood flow across the tissues of your body. This is because exercise stimulates the blood vessels to create a powerful, flow-regulating molecule called nitric oxide. As the flow improves, the body makes new blood vessels, which penetrate deeper and deeper into the tissues of the body. This allows more access to the bloodstream’s goods and services, which include food distribution and waste disposal. The more you exercise, the more tissues you can feed and the more toxic waste you can remove,” (pp. 21 & 22).
“All of the evidence points in one direction: Physical activity is cognitive candy,” (p. 22).
For more information, Dr. Medina has a brief and entertaining video on this subject Exercise: Good for brain and body.