How physical exercise strengthens your brain – 04/07/2024 – Balance

Growing up in the Netherlands, Henriette van Praag was always 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, she discovered that exercise can stimulate the growth of new brain cells in mature mice. After that, her relationship with physical exercise changed.

“I started taking it more seriously,” said van Praag, now an associate professor of biomedical sciences at Florida Atlantic University. Today, this involves doing CrossFit and running 8 to 10 km several days a week.

Whether exercise can cause new neurons to grow in adult humans — a feat previously thought impossible and a tantalizing prospect for treating neurodegenerative diseases — is still up for debate. But even if it’s not possible, physical activity is great for your brain, improving mood and cognition through “a multitude” of cellular changes, says van Praag.

What are the benefits?

Exercise provides short-term boosts in cognition. Studies show that immediately after a session of physical activity, people perform better on tests of working memory and other executive functions. This may be in part because movement increases the release of neurotransmitters in the brain, particularly epinephrine and norepinephrine.

“These molecules are necessary to pay attention to information,” says Marc Roig, associate professor in the School of Physiotherapy and Occupational Therapy at McGill University. Attention is essential for working memory and executive function, he added.

Dopamine and serotonin, which are neurotransmitters, are also released with exercise, which may be the main reason why people often feel so good after running or cycling for a long time.

The benefits for the brain 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 adds the caveat that the effects on cognition are not huge, and not everyone improves to the same extent. “You can’t get a super memory just because you exercised,” he said.

Physical activity also benefits mood. People who exercise regularly report having better mental health than sedentary people. And exercise programs can be effective in treating depression, which leads some psychiatrists and therapists to prescribe physical activities. A good reference is from the Centers for Disease Control and Prevention, which recommends 150 minutes of moderate aerobic activity or 75 minutes of vigorous aerobic activity per week.

Perhaps most notably, exercise offers protection against neurodegenerative diseases. “Physical activity is one of the healthy behaviors 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.

How does exercise do all this?

It starts with the muscles. When we exercise, they release molecules that travel through the blood to the brain. Some, like a hormone called irisin, have “neuroprotective” qualities and are linked to the cognitive health benefits of exercise, said Christiane Wrann, an associate professor of medicine at Massachusetts General Hospital and Harvard Medical School who studies irisin. . (Wrann is also a consultant for a pharmaceutical company, Aevum Therapeutics, that hopes to harness irisin’s effects in a medicine.)

Good blood flow is essential to obtain the benefits of physical activity. And conveniently, exercise improves circulation and stimulates the growth of new blood vessels in the brain. “It’s not that there’s an increase in blood flow,” Voss said. “It’s just that there is a greater chance of signaling molecules, which come from the muscle, being delivered to the brain.”

Once these signals are in the brain, other substances are released locally. The star of the show is a hormone called brain-derived neurotrophic factor, which is essential for the health of neurons and the creation of new connections — called synapses — between neurons. “It’s like fertilizer for brain cells to recover from damage,” Voss said. “And also for the synapses on the nerve cells to connect with each other and sustain those connections.”

A greater number of blood vessels and connections between neurons can increase the size of different areas of the brain. This effect is especially noticeable in older adults, as it can compensate for the loss of brain volume that occurs with age. The hippocampus, an area important for memory and mood, is particularly affected. “We know it shrinks with age,” Roig said. “And we know that if we exercise regularly, we can prevent this decline.”

The effect of exercise on the hippocampus may be one way to help protect against Alzheimer’s disease, which is associated with significant changes in this part of the brain. The same goes for depression; The hippocampus is smaller in depressed people, and effective treatments for depression, including medication and exercise, increase the size of the region.

What type of exercise is best for your brain?

Experts emphasize that any exercise is good and the type of activity doesn’t seem to matter, although most research has involved aerobic exercise. However, they added that higher intensity workouts appear to confer a greater benefit to the brain.

Improving your overall level of cardiovascular fitness also appears to be key. “It’s dose-dependent,” Wrann said. “The more you can improve your cardiorespiratory fitness, the greater the benefits.”

Like van Praag, Voss incorporated his research into his life, making a conscious effort to engage in higher-intensity exercise. For example, on busy days when she can’t fit in a full workout, she looks for hills to bike up on the way to work. “Even if it’s a little,” she said, “it’s still better than nothing.”

This article was originally published in The New York Times.