Introduction

Imagine that your doctor told you that there was a simple, virtually side-effect-free treatment that would allow you to live a longer and better life. A treatment that significantly reduced the risk of diseases such as heart attack, stroke, diabetes, cancer, depression and dementia. The treatment would also improve your memory, help you cope with stress, enhance your creativity and probably make you more intelligent.

This sounds too good to be true. If such a treatment existed, I would have heard about it, you might think. But, the treatment does exist. It's not new either. We've known about it for thousands of years. I'm talking about physical activity.

It's common knowledge that physical activity is good for our bodies. Physical activity lowers blood pressure, reduces cholesterol levels and improves blood sugar regulation. Perhaps you already knew this?

What few people realise is that our brain is probably the organ most affected by physical activity. Put simply, our brains are completely dependent on physical activity to function optimally. Your brain is simply upgraded to a better version by being physically active.

Although we've known for a long time that exercise is good for your mood and mind, research has shown us why physical activity is so important for our brains. When we move our muscles to increase our heart rate, a number of chemicals are released that affect all of our tens of billions of nerve cells. These substances are the closest thing we have to miracle cures. Recent research has shown that the chemicals released during physical activity strengthen all areas of our brain. This explains the enormous effects physical activity has on brain function. It's no exaggeration to say that the most important thing you can do for your brain is to be active. Physical activity will not only make you feel better, but will also have a positive effect on stress management, learning, memory, creativity, concentration and intelligence. In addition, an active life will protect you from depression and anxiety and significantly reduce the risk of brain diseases such as dementia, Parkinson's and stroke. The research leaves no doubt: Physical activity makes your brain both healthier and faster.

Memorisation

All parts of our brains are affected by physical activity, but the hippocampus, the brain's memory centre, seems to be in a class of its own when it comes to the degree of impact. The hippocampus is a small banana-shaped structure, located deep inside the brain, which is of crucial importance for learning and memory. The structure shrinks by about one per cent per year as part of a normal ageing process.

The results of the research caused the scientists to open their eyes. In this case, the hippocampus had grown by around two per cent during a year of fitness training. Think about that! Instead of getting one year older, their hippocampus had become two years younger, size-wise. How was that possible? BDNF, of course. When BDNF was measured in the blood of the participants, it was clearly higher in the training group than in the control group. When the groups were tested, it turned out that the exercise group scored clearly better on memory tests. Physical activity leads to increased production of BDNF, which stimulates growth of the hippocampus, which in turn makes us remember better. Quite simply, moving improves our memory!

Inactivity in school

According to the World Health Organisation (WHO), inactivity is the biggest global public health problem of the 21st century. Too much sitting is proving to be as dangerous as smoking. In large parts of the world, including Norway, we are sitting ourselves to death. We're now seeing a trend in the western world where, for the first time, children and young people are in danger of living shorter lives than their parents.

It's unnatural for children to sit still for long periods of time. Given the opportunity, they want to play and move. Unfortunately, with all the sedentary behaviour in the classroom, schools are helping to unlearn physical activity in our children. This is both unnatural and dangerous to their health. All children are dependent on regular play and physical activity in order to develop normally.

More than twice as many Norwegian 7- and 8-year-olds have motor problems today than five years ago. Motor development is important for children's self-image, popularity and status among other children and, not least, for mastering practical tasks in everyday life. Several studies also show a link between motor problems and other challenges such as social problems, poor self-image and anxiety/nervousness.

We've known for a long time that physical activity and play are important for children's physical development. What we have realised relatively recently is how important physical activity is for our children's brains to develop normally and function optimally. Active schoolchildren learn more, thrive better and are less likely to be bullied. In addition, we see that children who fulfil the authorities' recommendations of one hour of physical activity and play every day become more concentrated, are less sensitive to stress, have better memory and learn better.

The knowledge is so new, and revolutionary, that it has not yet had a full impact on professionals and politicians. Fortunately, Norwegian politicians have taken action and recently decided ".... to introduce a scheme that ensures pupils in grades 1-10 have at least one hour of physical activity every day within the current timetable."

Depression

Knowledge about how physical activity can be used to treat depression is more important than ever. Around 20 % of all Norwegian women and 10 % of all Norwegian men will experience depression requiring treatment during their lifetime. And the frequency is increasing. Depression is one of the most common diseases worldwide and an important reason for sick leave and disability in Norway. Few diseases create as much suffering for individuals and the people around them, and drain society of as many resources, as depression.

You may already have heard of the Nord-Trøndelag Health Study (HUNT)? This is one of the world's largest health surveys, in which more than 120,000 people in Trøndelag have consented to (anonymised) health information about them being made available for research. In October 2017, an article from the HUNT study was published in the renowned American Journal of Psychiatry. Researchers had followed over 33,000 healthy Norwegians for eleven years. A range of data was recorded from these subjects, including how physically active they had been. They then looked at how many had developed depression during these eleven years, and found a significant reduction in the incidence of depression among those who were physically active. To put it another way: Physical inactivity is a significant risk factor for depression. An inactive person had a 44 % higher risk of developing depression over these eleven years than someone who was physically active. This was to be expected, as several larger studies have previously shown similar results. What was surprising, however, was how little physical activity was needed to prevent the development of depression. One hour of physical activity per week was enough. The intensity of the activity turned out not to matter. In other words, it takes much less to prevent depression than to treat it.

The great training paradox

With all the knowledge we have today about how important movement is for both the body and the brain, it would be natural to believe that we all live physically active lives. This is not the case; the majority of Norwegians are either completely inactive or not active enough to benefit their health. What is it that makes most of us live a sedentary life despite knowing that it is not good for us?

There are several reasons for this paradox, but there is one explanation that I think is very underestimated, namely that evolution has predisposed our brains to laziness. Our first ancestors were physically active because it was necessary for survival. At the same time, evolution has made us lazy and fond of being quiet when the opportunity arises. Our ancestors lived in a time when food was scarce, so to survive it was important to conserve energy and not waste it on unnecessary activity. To put it another way: We're made to run, but no more than is absolutely necessary for survival. The problem in modern society, and a major cause of the current epidemic of obesity and inactivity, is that physical activity is no longer necessary. We have free access to food, no natural enemies, and if we want to go somewhere, we have cars, escalators and lifts to take us there, with minimal consumption of calories. We've managed to completely remove the need for movement in everyday life. What we are left with is a brain that is lazy and wants us to be still. No wonder so many people struggle to get out and get active - their brains do everything they can to make them choose the sofa over trainers.

This doesn't mean we should just give in to our brain's laziness. It is entirely possible to overcome our evolutionary urge to be lazy and get active. The benefits are tremendous: a longer and better life and a strengthening of virtually all brain (and body) functions.

From bestselling "Strong brain with an active body" of Ole Petter Hjelle