Exercised: The Science of Physical Activity, Rest and Health

by Daniel E. Lieberman

Altogether, regular physical activity alters brain chemistry, enhances electrical activity, and improves brain structure.

Among other differences, the brains of more physically active people have enlarged memory regions, more cells, and increased blood supply.

As we have previously seen, regular physical activity lowers overall reactivity to stressful situations, keeping down chronic levels of cortisol, which has noxious effects on the brain.

May be the reason of resilience

Altogether, exercise can improve confidence and our belief in the ability to achieve our goals (self-efficacy).

Given these somber statistics, there needs to be wider recognition that regular physical inactivity is a mismatch that sometimes increases people’s vulnerability to many diseases of the mind including dementia, depression, and anxiety.

If you want to maximize levels of BDNF in your brain as a form of prevention, cardio appears to be more effective than weights, especially if you do high-intensity workouts.

Some studies find that self-selected doses of exercise are more effective than specific prescribed doses,

That avoidance makes sense because, as we have seen from the very start of this book, exercise is a fundamentally strange and unusual behavior from an evolutionary perspective.

But as the last few decades have shown, we won’t succeed solely by medicalizing and commodifying exercise; instead, we should treat exercise the way we treat education by making it fun, social, emotionally worthwhile, and something that we willingly commit ourselves to do.

The widespread, collective benefits of physical activity aren’t always obvious until we face the consequences of its absence.

Researching and writing this book has convinced me that a philosophy for how to use one’s body is just as useful as a philosophy for how to live one’s life.

By following deep and ancient instincts to avoid the discomfort that comes with physical exertion, we increase the chances we will senesce faster and die younger, and we become more vulnerable to many diseases and chronic, disabling illnesses.

But thanks to our evolutionary history, lifelong physical activity dramatically increases the chances we will die healthy after seven or more decades.

So on cold, miserable mornings when I am exercised about exercise and struggle to head out the door for a run, I remind my brain, which thinks the rest of my body is a vehicle for moving it from place to place, that it really evolved to advise my body on when and how to move. Fortunately, that advice can be boiled down concisely and simply.

Make exercise necessary and fun. Do mostly cardio, but also some weights. Some is better than ...

For a terrific exploration of these challenges among Western athletes, see Hutchinson, A. (2018), Endure: Mind, Body, and the Curiously Elastic Limits of Human Performance (New York: William Morrow).

James, W. P. T., and Schofield, E. C. (1990), Human Energy Requirements: A Manual for Planners and Nutritionists (Oxford: Oxford University Press).

I am sorry to report that an entire day of intense thinking amounts to only twenty to fifty extra calories, about what you get from eating half a dozen peanuts.

A common formula for maximum heart rate is to subtract your age from the number 220, but for healthy adults a better equation is 208 – 0.7 • age.

Another classification is based on measuring energy use from oxygen using METs (metabolic equivalents) in which 1 MET is the rate of energy used during quiet sitting, usually 3.5 milliliters of oxygen per kilogram of body weight per minute.

By this convention, sedentary activity is 1 to 1.5 METs, light is 1.5 to 2.9 METs, moderate is 3 to 6 METs, and ...

As an example, one worldwide best-selling book claimed that wheat and other foods with gluten cause inflammation of the brain. The data, however, indicate that unless you have celiac disease, eating wheat (especially whole wheat) or other grains will not cause your body, including your brain, to become inflamed unless you eat too much and become obese.

The body’s main energy store are adenosine molecules with three phosphates attached: ATP (adenosine triphosphate). When ATPs break down, releasing energy, adenosine molecules slowly accumulate in the brain, helping make you drowsy. Caffeine keeps you awake by binding to the receptors in the brain that normally bind to adenosine, blocking their effect.

The brain is bathed in cerebrospinal fluid that keeps blood away from brain cells. This is because direct contact with blood destroys neurons (as, for example, during a stroke). In addition, by keeping blood away from direct contact with the brain, the blood-brain barrier prevents infectious agents and toxins in the bloodstream from getting into the brain.

Some muscle men and women think they need to eat enormous amounts of protein to supply their growing, strapping muscles. Careful studies, however, find that the added muscle mass power lifters pack onto their bodies requires only about an additional 20 percent more protein than needed by elite endurance athletes like distance runners.

Apparently, a two-hundred-pound bodybuilder gets little benefit from consuming more than about four to five ounces of extra protein. Further, the body cannot store excess protein but instead must break it down and excrete it. Consequently, protein overconsumption can potentially lead to a variety of troubles, especially for the kidneys.

A caveat to this inference, however, is that exercise doesn’t affect bones as simply as muscles. If I were to work out my upper body in the gym for the next year, my biceps and triceps would bulk up noticeably, but my arm bones would thicken almost imperceptibly. Unlike muscles, bones primarily grow bigger in response to loads only during youth.

If you want to learn the science behind how to train like Batman, check out Zehr, E. P. (2008), Becoming Batman: The Possibility of a Superhero (Baltimore: Johns Hopkins University Press).

The tendency to postpone long-term benefits for short-term alternatives is known as temporal discounting. Economists and psychologists have shown this is a common behavior that leads people to make irrational decisions.

Several studies have identified genes associated with avoiding physical activity.

Many studies find that physical activity levels and socioeconomic status are inversely related.

It is widely agreed that children should get at least 300 minutes per week, but the worldwide average is 103 minutes a week for primary schools and 100 minutes a week for secondary schools.

Although widely used, BMI has many problems including not making a distinction between fat and muscle mass. Waist circumference or, even better, the ratio of waist circumference to height is generally a better measure of how much organ visceral fat you have. That said, BMI accurately categorizes people’s percentage of body fat about 82 percent of the time.