Who knew? Exercising strengthens your muscles and your brain
Evolutionary scientists have long believed that those in good physical health also possess better mental health. Humans are mobile creatures, the thinking goes, and over the centuries our brains developed with our bodies. You can’t ignore one without harming the other.
“From an evolutionary perspective, it’s all about adapting,” says Dr. John Ratey, clinical associate professor of psychiatry at Harvard Medical School and co-author of the forthcoming book Spark: The Revolutionary New Science of Exercise and the Brain. “A big part of adapting is learning, and a big part of learning is moving well and moving fast enough to get out of the way of the tiger.”
That makes sense. But how are physical and mental health linked at the molecular level? Recent advances in medical technology have allowed a better understanding of how the brain operates, and many studies are under way in both lab animals and humans. These efforts are producing a raft of evidence that what’s good for the body is also good for the mind.
Sweating It Out
Exercise, it turns out, benefits the brain in two major ways. First, it helps generate new brain cells. And second, it strengthens the connections between those cells, providing more mental agility and actually allowing the brain to stay young even as the body ages.
One of the more encouraging discoveries of recent years is that the body continues to create new brain cells later in life. The general assumption had been that after midlife (around 50 years of age) the production of brain cells slows markedly, leaving the aged trying to do more with less. But it’s now understood that brain cell production — called neurogenesis — can occur throughout life, even as we advance into old age.
However, neurogenesis doesn’t occur at an equal rate in every person or throughout the different times in one’s life. Among the variables affecting the rate of production is exercise. Each time a muscle tenses and relaxes, it releases various chemicals into the body. Among these is a protein called IGF-1 that, when it is conveyed through the bloodstream to the brain, helps organize the production of other beneficial chemicals called “neurotrophic factors.”
One neurotrophic factor, BDNF, or “brain-derived neurotrophic factor,” prompts brain cells to reproduce with remarkable speed. Ratey has called BDNF “Miracle-Gro for the brain,” and a brain surging with BDNF, researchers say, has healthy cells with numerous branches, making it better equipped to process new information. A brain with scant amounts of this chemical closes itself off to new information, and memory tends to suffer as well.
However, intelligence is not just a matter of more cells. “Neurogenesis without connectivity doesn’t work,” says Fernando Gómez-Pinilla, a professor of neurosurgery and physiological science at UCLA. “The cells need to make the connection.”
Our brains consist of the gray matter responsible for information processing, but also include white matter, made up of nerve cells that allow the transmission of information between brain cells. Exercise also aids in maintaining and improving these connections — or what’s called the synaptic plasticity of the brain. People who exercise have higher levels of neurotrophins, resulting in a brain that’s able to function with more agility.
Researchers have found that the positive impacts of exercise on the brain come quickly. In under an hour, improvements in mental fitness often kick in, with synapses firing more efficiently.
Time to Get Physical
These discoveries are the good news. The bad news? Well, the benefits of exercise tend to fall off fairly quickly. People have to keep at it, and these days Americans often don’t place much of a premium on physical fitness. We may be getting not only slower, but also slower on the uptake.
Evolutionary pressures no longer require that we be in top physical shape at all times. We don’t need to elude predators to stay alive, and there’s every reason to give into the siren song of the Barcalounger. As a result, Americans are becoming more sedentary — and thus not only more susceptible to obesity and other diseases, but also to slowing mental function.
If the allure of remaining mentally sharp into old age isn’t enough to get you off the couch, here’s more incentive. Recent studies suggest — though have not yet proved — that some of the same molecular mechanisms that keep the brain pliable may also slow the onset of Parkinson’s and Alzheimer’s diseases. These conjectures remain controversial, but the early research is promising.
In any event, experts say that regular exercise can ensure a fuller life as we age, both physically and mentally. That’s increasingly important as each generation outlives the last. For example, a child born in the United States in 2004 can expect to live to 77.9 years of age, or nearly 10 years longer than someone born in 1950. Fortunately, good results don’t require a Quantico-level exercise regimen. Even just a few hours a week of brisk walking can help sustain body and mind.
Although the optimal amount of exercise is still a matter of debate, researchers agree on one thing: “Any exercise is better than no exercise,” says Gómez-Pinilla. “I’m talking about even a minimal amount of exercise. For example, if you need to go to the next floor, don’t take the elevator. Walk.”
Gómez-Pinilla is quick to add that physical conditioning is really just one selection on a menu of sensible lifestyle choices that promote a better-functioning mind. A healthy diet and a regimen of sound sleep also help to conserve and improve mental powers. Gómez-Pinilla believes that the role of diet in brain health will receive far more attention as new discoveries crop up in coming years.
While your mileage may vary, the important point is that by making the right decisions, you can subtly take control and alter your aging process, keeping your mind sharp. And that, at least, is a positive prognosis for those who see the calendar chiefly as a harbinger of bad news.
“The big impact is not just that we’re making those new cells, but that it signifies growth rather than death,” says Ratey. “If you’re not in the business of growing, you’re in the business of dying.”
— Wayne Curtis
