Why is exercise good for you? A reasonable question that, at first, might seem obvious. When we exercise, we burn calories and lose weight. Okay, but does simply being lighter make us healthier? I know some older people who weigh in at around 90 pounds, and they are not healthy. You might say, then, that exercise strengthens your heart by making it beat faster; well, we should all have heart failure then. Well what about our muscles? When we exercise, our muscles get stronger, right? In reality, our muscles are torn down during prolonged use. All of these statements are true. It turns out that the benefits of exercise all have to do with the body’s amazing ability to adapt.
A few years ago, I read an article about Chilean miners that worked at an elevation of about 12,000 feet. Over time, they developed higher levels of hemoglobin in their blood, and their chests grew in response to greater lung growth. Both of these modifications increase the oxygen-carrying capacity of the blood, enabling the miners to work more efficiently.
All of the adaptations the miners experienced were the result of a protein in the body called NRF-2. When we exercise, we break down tissues; muscle, tendons, ligaments, bone, cartilage, and even blood get damaged. All of this damage causes an increase in free radical production in the cells, which, in turn, stimulate NRF-2 to then unleash a genetic cascade of over 2,000 genes known as 
“survival genes.” It is the survival genes that cause our bodies to rebuild muscle bigger than it was before the damaging event, making our heart, tendons, and ligaments a little stronger after each exercise session. It is by this mechanism that we can actually have some small control over our “evolution,” by actually altering our genes. This improved survival stimulated by small repetitive “damaging events” is termed hormesis, and it is an area that thousands of researchers around the world are focusing on.
What’s really fascinating is that it now appears that we can pass this “evolved” genetic structure to our kids. More on that in my blog next week.