Nova YorkScientist Henriette van Praagh, born in the Netherlands, was always very active: when she was young she played sports and biked to school every day. In the late 1990s, while working as a scientist at the Salk Institute for Biological Studies in San Diego, she discovered that exercise could stimulate the growth of new brain cells in older mice. Since then, his attitude towards exercise has changed. “I started taking it seriously,” says Van Praagh, now an associate professor of biomedical sciences at Florida Atlantic University. For her these days, that means doing CrossFit and running eight or nine miles a few days a week.
However, in adult humans, there is still debate about whether exercise can cause the growth of new neurons, something that was previously thought to be impossible but is an enticing prospect for the treatment of many neurodegenerative diseases. But even if that’s not possible, physical activity is good for the brain, because it improves mood and cognition through “a large number” of cellular changes, Van Praagh points out.
What are some benefits?
Exercise improves short-term 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 due in part to the fact that movement promotes the release of neurotransmitters in the brain, particularly epinephrine and norepinephrine. “These types of molecules are essential for paying attention to information,” says Marc Roig, a Catalan researcher and associate professor in the Faculty of Physical Therapy and Occupational Therapy at McGill University. Attention is essential for working memory and executive functioning, he adds.
The neurotransmitters dopamine and serotonin are also released with exercise, which is thought to be one of the main reasons why people tend to feel good after going for a run or a long bike ride. However, the brain benefits really start to show when you exercise consistently over time. Studies prove this People who exercise several times a week get, on average, better results on cognitive tests than people who don’t exercise. Other research has found this A person’s cognition tends to improve After participating in a new aerobic exercise program for several months. Roig highlights the caveat that the effects on cognition are not huge and not everyone improves to the same degree. “You can’t gain super memory just by exercising,” he says.
in other hand, Physical activity also improves mood. People who exercise regularly claim to have better mental health than sedentary people. Exercise programs can be effective in treating depression, leading some psychiatrists and therapists to prescribe physical activity. A good starting point is the recommendation to do 150 minutes of moderate aerobic exercise or 75 minutes of vigorous aerobic exercise per week.
Perhaps most notably, exercise provides protection against some neurodegenerative diseases. “Physical activity is one of the health behaviors that has been shown to be most beneficial to cognitive function and reduce the risk of Alzheimer’s disease and dementia,” explains Michelle Voss, assistant professor of psychological and brain sciences at the University of Iowa.
How does exercise achieve all this?
The process begins with the muscles. When we exercise, muscles release molecules that travel through the blood to the brain. Some, like a hormone called irisin, have “neuroprotective” qualities and have been shown to be linked to the benefits of exercise for cognitive health, says Christiane Wran, an assistant professor of medicine at Massachusetts General Hospital and Harvard Medical School, who studies irisin. Ran is also an advisor to the pharmaceutical company Aevum Therapeutics, which hopes to harness the effects of irisin in medicine).
Good blood flow is essential to getting the benefits of physical activity. Conveniently, exercise improves circulation and stimulates the growth of new blood vessels in the brain. “It’s not just about increasing blood flow,” Voss points out. “The problem is that there’s more potential for signaling molecules from the muscles to get to the brain.”
Once these signals reach the brain, other chemicals are released locally. The star of the show is a hormone called brain-derived neurotrophic factor, or BDNF, which is essential for nerve cell health and the creation of new connections — called synapses — between nerve cells. “It acts as a fertilizer for brain cells to recover from damage,” Vos explains. “And also so that the synapses of neurons communicate with each other and maintain these connections.”
Having a greater number of blood vessels and connections between neurons can increase the size of different brain regions. This effect is especially noticeable in older people because it can compensate for the loss of brain volume that occurs with age. The hippocampus is particularly affected, an area important for memory and mood. “We know that it decreases with age,” Roig says. “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 people with depression, and effective treatments for depression, including medications and exercise, increase the size of this area.
What exercise is best for the brain?
Experts stress that any exercise is good and the type of activity does not seem to matter, although most research has focused on aerobic exercise. However, they add that more intense exercise seems to bring more benefits to the brain. It also appears to be key to improving overall cardiovascular health. “It depends on the dose,” Wran says. “The more you can improve your cardiorespiratory capacity, the greater the benefits.” Like Van Praagh, Vos integrated his research into daily life, making a concerted effort to exercise more intensely. For example, on busy days when you can’t train as much as you could, find ramps to bike to work. “Even if it’s a little, it’s better than nothing.”
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