Mar 12, 2026
3 min read
The expert argues that movement has beneficial effects on our cognitive ability, "especially if you have been sedentary all your life and started doing this when you were very old."
José Luis Trejo, neurologist: "There is no antidepressant more effective than exercise for depression and anxiety"
Experts maintain that movement has a beneficial effect on our cognitive abilities, "even if you have been sedentary all your life and start doing so when you are very old."
March 11, 2026. Updated at 05:00 AM.Physical exercise is not just a physical activity, but a fundamental tool to train, protect and strengthen the brain throughout life and even beyond a generation.This is defended by José Luis Trejo, a neuroscientist who brings his research work to the Cajal Neuroscience Center of the Superior Council of Scientific Research (CSIC), which also relies on scientific evidence to defend the key idea: movement is an essential biological need for mental, cognitive and emotional health.He recently published Neuronas en march (geoPlaneta Ciencia, 2026), a work of scientific dissemination that deals with physical training at several levels.
- When we talk about physical activity, what is considered light, moderate or vigorous?
—Indeed, from an academic perspective, this is a complex issue that when you talk to the average person, they don't always understand. Because if we talk about METs, metabolic equivalents, they are concepts that people don't understand - it's a unit of measurement used to quantify energy expenditure and intensity of physical activities. But a scientifically validated option that anyone can do is to count the heart rate you can saywhen walking, for example, or when running at a low intensity. Because the heart rate we have when speech sounds compete with breathing is just the optimal level for physical activity.
For example, if a person begins to walk softly, they may speak quietly.As you start walking faster and faster, there comes a point where breathing becomes difficult.When this happens, this is the heart rate your heart needs for healthy exercise.If we run faster, of course there will come a time when we can no longer speak, but we don't care about that anymore.
- Why is it no longer important?
- Because it is a very strong exercise.And if it continues, it will get tired.You can know for yourself how much exercise you need to do to get all the benefits for your brain, without becoming stressed.
— He comments that moving is not mandatory, it is a biological necessity.
- Yes.Over millions of years of evolution, the brain has fine-tuned its function.Along with the moving body it is accustomed to receiving information from the various places it passes.Metabolism, repair, blood flushing, and energy and fueling of neural cells, neurons, and astrocytes, mitochondria function all based on movement.Of course, there are no creatures that move all the time, and you should alternate rest periods.The problem is that when we use less of our neural resources for active life, the brain begins to atrophy.It is very simple.What's more, a sedentary brain has all the symptoms and all the phenotypic parameters of an aged person.
- What is a sedentary lifestyle?Do you think we have the wrong idea?
- Yes, because various recent scientific discoveries have shown that there are many types of sedentary lifestyles.It's not just about not exercising, it's about sitting for too many hours to rest your heart rate.In addition, there are two types of sedentary lifestyle: mentally active and inactive, the latter is even worse.
- I mean, can you still sit for eight hours at work and go to the gym?
-If you exercise for an hour at the gym every day, you will do very well because you are moving your joints and your brain.The problem is that those are eight hours where you only get up to go to the bathroom, get coffee, and little else.Because this causes brain damage, metabolic problems, dehydration and premature aging, whether you exercise for an hour at the gym every day or not.Therefore, the ideal is to minimize the time spent sitting in addition to exercising for that hour per day.The person may not have the money, ability or even time to go to the gym, but then finding a way to get up and move around for four minutes every hour is crucial.If you're in a building, go up or down two or three floors and get your heart rate up a little.
- When it comes to physical exercise, more is better?
- The belief that "more is better" comes from the fact that we have always paid attention to the body, the physiology of the body.Indeed, there are many components and organs in the body that benefit greatly from exercise.But as neurobiologists, we study the brain, and it has a response curve that differs from the rest of the body.By the way, not all muscles use "more is better".There is no benefit.Many elite athletes often suffer from heart disease as a result of overtraining.
-Does the same thing happen in the brain?
- Yes, when we go to a certain point - each person has his own needs - what we see is that we have lost many of the benefits that we have gained through physical activity.
- The most surprising effects are, first of all, it increases synaptic efficiency.Synapses are the connection points of one neuron to another in a neural circuit.And through this mechanism one neuron talks to another and transmits information to it.Fast and accurate, this is how our thoughts are formed.This increases synaptic efficiency, which is similar to the fact that our thoughts flow better.Also, to give us an idea of another very important effect, it increases dendritic arborization, which is that of neurons synapsing on the surface, and one neuron talking to another.That is, not only do they speak better, but there are more places to speak.Suddenly, not only do people speak louder and more clearly, but more people seem to speak.
The third thing is that all this has to be fed.Neurons and astrocytes need more energy to function.Exercise increases the efficiency of mitochondria, the organelles that feed and function neurons and astrocytes.This whole panorama is talking about the neurons you already have in your brain.But it also exercises neurogenesis in adults.
- What do you say creates neurogenesis in adults?
— This has been known since the end of the 90s until now.In the adult brain, there are small areas where neurons are still functioning.And although they are small, they are not insignificant, because one of them is the hippocampus region, which is actively involved in learning and memory, but also in mood, tension and anxiety.The number of neurons in the hippocampus, some are formed in an adult.And look at the surprise, this is where new neurons are born, which is one of the areas of the brain that is focused on physical activity.The health of the neurons and cells of the hippocampus is improved by movement, which also increases the number of stem cells living in it.in the hippocampus.So when you exercise, not only better neurons, but more neurons.And we call this neurogenesis.
- So I think it's important to exercise even as you get older.
- It is important for two reasons.First, it has been shown, and a Spanish group has recently done so, that this formation of new neurons, this neurogenesis, is found even in the elderly.It is less than in young people, but it exists.And the interesting thing is that exercise has beneficial effects on our cognitive ability, even if you have been sedentary all your life and even if you start exercising when you are very old.You can always reduce and delay the onset of symptoms of neurodegenerative diseases.
Could exercise be more effective than some medications?
- Well, I don't really know, or I, at least, I don't know of any antidepressant or anxiolytic drug that is more effective for depression and anxiety than moderate physical exercise.And it has no side effects.
- One surprising thing you address in the book is that exercise is inherited, right?
-It's very funny;Many find it hard to believe.Exercise is inherited.What needs to be explained are certain biological variables that are conditioned by the intergenerational inheritance of that acquired character and others that are not.In fact, my five fingers are so firmly imprinted in my genes that even if I lose one, my children will have five.Instead, the number of neurons in a rat's brain depends on its lifestyle, movement behavior, and whether it moves more or less.And it's genetically programmed, it's programmed in such a way that this acquired character can be inherited epigenetically.That is, if the mouse runs more and has more neurons in its hippocampus, its offspring, even if they are sedentary, will have more neurons in the hippocampus.
