Growing up in the Netherlands, Henriette van Praag had always been active, playing sports and cycling to school every day. Then, in the late 1990s, while working as a scientist at the Salk Institute for Biological Studies in San Diego, California, she discovered that exercise can stimulate the growth of new brain cells in mature mice. After that, her approach to exercise changed.
“I started taking it more seriously,” said Van Praag, now an associate professor of biomedical sciences at Florida Atlantic University. Nowadays, that means doing CrossFit and running 5 miles a few days a week.
It is still a matter of debate whether exercise can cause new neurons to grow in adult humans, a tantalizing prospect for treating neurodegenerative diseases. But even if it's not possible, physical activity is great for the brain, improving mood and cognition through “a huge number” of cellular changes, Van Praag said.
Studies show that immediately after physical activity, people score better on tests of working memory and other executive functions. This may be because movement increases the release of neurotransmitters in the brain, such as epinephrine and norepinephrine.
“These kinds of molecules are necessary to pay attention to information,” said Marc Roig, an associate professor at the School of Physical and Occupational Therapy at McGill University in Montreal.
The neurotransmitters dopamine and serotonin are also released with exercise, which is believed to be one of the main reasons why people often feel good after going for a run or a long bike ride.
However, the brain benefits really start to emerge when we exercise consistently over time. Studies show that people who exercise several times a week score higher on cognitive tests, on average, than more sedentary people. Other research has found that a person's cognition tends to improve after participating in a new aerobic exercise program for several months.
Roig added the caveat that the effects on cognition are not huge. “You can't develop a super memory just because you exercise,” he said.
People who exercise regularly report having better mental health than sedentary people. And exercise programs can be effective in treating depression.
The US Centers for Disease Control and Prevention's recommendation of 150 minutes of moderate aerobic activity or 75 minutes of vigorous aerobic activity per week is a good reference.
“Physical activity is one of the health behaviors that has been shown to be most beneficial for cognitive function and reducing the risk of Alzheimer's and dementia,” said Michelle Voss, associate professor of psychological and brain sciences at the University of Iowa.
The star is a hormone called brain-derived neurotrophic factor, or BDNF, which is essential for the health of neurons and for creating new connections — called synapses — between neurons.
“It's like fertilizer for brain cells to recover from damage,” Voss said.
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