摘要：New research suggests the connection between exercise and the brain goes deeper than you might think. These six kinds of movement can help make you more creative, boost your self-esteem and reach altered states of consciousness
FILTER-FEEDERS aside, humans are the only creatures that can get away with sitting around all day. As a species, we have been remarkably successful at devising ways to feed, entertain ourselves and even find mates, all while barely lifting a finger.
True, this is a sign of just how clever and adaptable we are. But there is a huge cost to our sedentary ways, not only to our bodies, but also our minds. Falling IQs and the rise in mental health conditions have both been linked to our lack of physical movement.
But the connection between movement and the brain goes deeper than you might think. A revolutionary new understanding of the mind-body connection is revealing how our thoughts and emotions don’t just happen inside our heads, and that the way we move has a profound influence on how our minds operate. This opens up the possibility of using our bodies as tools to change the way we think and feel.
Evidence is starting to stack up that this is indeed the case, and it isn’t all about doing more exercise. In my new book, Move! The new science of body over mind, I explore emerging research in evolutionary biology, physiology, neuroscience and cell biology to find out which body movements affect the mind and why.
Whatever it is that you want from your mind – more creativity, improved resilience or higher self-esteem – the evidence shows that there is a way of moving the body that can help. Here is my pick of the best ways to use your body to achieve a healthier, better-functioning mind.
Get on your feet
It isn’t exactly news that walking and running help to clear the mind, but research into the reasons why these activities affect our heads suggests that different speeds provide different mental benefits.
Running or walking at a pace that feels easy to you allows the mind to wander by temporarily reducing activity in the prefrontal regions of the brain. These areas favour rational, straight-line thinking, and studies suggest that reducing their activity allows broader, more creative ideas to flow.
The effects spill over for at least 15 minutes after you have finished walking, according to researchers at Stanford University, California, who speculated that a walk before an ideas meeting could pay dividends. But there is a catch: walkers performed slightly worse in tests of straightforward, linear problem-solving compared with those who remained seated.
Intriguingly, even the gentle pressure of footfall on a slow walk has a big impact on blood flow to the brain. Studies by Dick Greene at New Mexico Highlands University in Las Vegas and his colleagues suggest that when our feet hit the ground, their arteries are compressed. This increases turbulence in the blood, providing it with an extra rush towards the brain of up to 15 per cent.
Pick up the speed to a marching pace and things get even more interesting. In Greene’s experiments, the biggest boost to blood flow happened when people’s step rate and heart rate synchronised at 120 steps and 120 beats per minute, hinting at a possible sweet spot. What exactly this extra blood does when it gets to the brain is unclear, but we do know that exercise in general increases grey matter in the hippocampus, which is crucial for memory processing and spatial awareness.
All this makes sense if you consider that walking a lot, running a little and using our big brains to hunt and gather are what humans are built for. Anthropologist David Raichlen at the University of Southern California has said that we evolved to be “cognitively-engaged endurance athletes“, so it shouldn’t be surprising that our bodies are set up in a way that means moving and thinking are intertwined.
If you are a millennial, you might want to avoid picking a fight with your dad. Today’s men appear to be markedly weaker than their counterparts in the 1980s, according to a 2016 study in the US that measured maximum grip strength, which is a proxy for overall muscle strength. The next generation, it seems, are weaker still. A 2019 study found that 10-year-olds in England were 20 per cent weaker and had 30 per cent less muscle endurance in 2014 compared with children of the same age measured in 1998.
Sedentary lifestyles are almost certainly to blame, and it matters for our physical and mental health alike. People who are stronger in middle age have more grey matter and better memory a decade later. One explanation for this could be a hormone called osteocalcin, which is released from bones when we move against gravity in any form of weight-bearing exercise. In rodent studies, its release has been linked to the size and connectivity of the hippocampus. Studies in humans are ongoing, but there are signs that a lack of osteocalcin could be linked to age-related cognitive decline and neurodegenerative disease.
The benefits of being strong don’t stop there. It has been known for many years that physical strength is linked to higher self-esteem and a feeling of being capable in all walks of life.
One explanation for why physical strength provides mental resilience is that our sense of self – and, more importantly, our sense of what we can achieve in the world – is built on the foundations of our bodily sensations. Neuroscientist and philosopher Antonio Damasio at the University of Southern California says that as well as keeping tabs on heart rate, blood pressure and blood sugar levels, our body has an unconscious sense of the health and state of our muscles and bones. This “musculoskeletal division” constantly sends messages about the strength and agility of the body’s movement apparatus – the muscles, bones, tendons and ligaments that allow us to move. This then feeds into our implicit sense of what we can handle.
If that is the case, the decreasing levels of strength in modern society are troubling. It is tempting to think that this decline may even play into the epidemic of anxiety and mental health conditions that is affecting people of all ages – perhaps the message from the musculoskeletal divisions of our bodies is giving us nothing to feel confident about?
The good news is that we can update this body-mind conversation at any time. Strength training is emerging as a powerful tool to tackle depression and anxiety, even when it isn’t done as part of a wider fitness programme. This doesn’t have to involve going to a gym or even buying a set of dumb-bells; you can use your own body weight. Spending more time sitting on the floor, for example, is a good way to strengthen leg muscles, because at some point you have to stand up. Strong legs also boost balance and coordination, both of which are suffering in our sedentary lifestyles.
The power of dance to bring humans together is so strong that some governments and religious groups around the world have tried to ban it at times.
It is a futile strategy. As a species, we are born to dance. Brain-imaging studies of newborns have shown that they notice if rhythmic music unexpectedly skips a beat. By the time they are 5 months old, this ability ties in with movement, too. Research shows that babies are able to move their bodies in time with music at this stage, and that the better they are at bopping along, the more they smile. Even at a tender age, moving to music seems to make us feel good.
“We are born to dance – even babies notice if rhythmic music skips a beat”
According to studies led by Morten Kringlebach at the University of Oxford, the feel-good factor is because our brains work as prediction machines that constantly make guesses about what is likely to happen next. In this view, a regular beat is satisfying because it makes it easy to predict what is coming. Each time we are correct, we get a small hit of dopamine, a neurotransmitter involved in feelings of pleasure.
Following the beat with your body provides a second dopamine hit, and may also create the illusion that our movements are producing the beat in the first place, says music psychologist Edith Van Dyck at Ghent University in Belgium, which makes us feel powerful and in control.
As such, moving to music when we are alone can make us happy. Doing it in a room with others takes things to the next level, adding the pleasure of social bonding into the mix, too.
Experiments with toddlers have shown that they are more likely to help an adult, by picking up a dropped item for instance, after being bounced in time to music, than after they have been bounced out of time with the beat. In adults, studies have shown something similar: moving in synchrony with others makes us more likely to care about them and share with them.
One proposal for how this happens is that we usually base our sense of self on our perception of our bodies’ movements. When we synchronise with other people, this “proprioceptive” sense gets blended with information about others’ movements coming in through our additional senses in such a way that the boundaries of self and other become temporarily blurred.
The result is a state of closeness and understanding, as well as a desire to help others – which sounds like something the world could really do with right now.
It is the smallest of movements, and you don’t need to be fit to do it. But controlling the muscles in your chest and diaphragm can make a big difference to the way you think and feel.
Incredibly, when you regulate your breath, what you are really doing is taking charge of your brainwaves and tying them to the rate at which air travels into and out of your nose.
This link comes via sensory neurons at the top of the nose, which fire when air flows past them. Because this air contains information about the outside world, it makes sense that activity in scent-related brain regions begins to synchronise with the breathing rate, allowing information to be processed as it comes in. Recent studies, however, have shown that this synchronisation doesn’t stop there. It spreads to areas involved in assigning meaning to the information, such as memory, and those involved in planning and decision-making.
Coordinated, rhythmic activity across different regions allows the brain to share information more easily. Some researchers believe that the brain’s ability to synchronise with breath may be a fundamental feature of the way it processes information.
The easiest way to put this into practice is to close your mouth and breathe at the rate of six breaths per minute: inhaling for 5 seconds, then exhaling for 5 seconds. Breathing at this pace has been shown to be the most efficient way to fill the air sacs of the lungs, where oxygen diffuses into the blood. This can raise oxygen saturation by a couple of per cent, enough to make a small difference to brain function.
Inhaling and exhaling six times per minute has also been shown to stimulate the vagus nerve, part of the parasympathetic nervous system, which resets the body to a state of calm after stress. Intriguingly, studies of religious chanting and prayer have found that they tend to slow breathing to six breaths per minute – which may explain why people find these practices calming.
At three breaths per minute, something else happens entirely. A 2018 study led by Angelo Gemignani and Andrea Piarulli of the University of Pisa, Italy, in which volunteers had air wafted up their noses to simulate breathing at a rate of three inhalations per minute found that brainwaves synchronised in the low-frequency delta and theta bands, particularly in brain regions involved in emotional processing. Theta waves are associated with deep relaxation and a state of “being” rather than “thinking”, a condition that was experienced by many of the study volunteers. So it seems that slow breathing is a free ticket to an altered state of consciousness, no added chemicals necessary.
A slouched posture has long been linked to negative thinking and feelings of defeat, according to psychological research, while an upright, expanded posture brings a more positive mental attitude. Experiments also show that holding the body upright during a stressful event helps people experience less stress and recover faster.
The problem is that, until recently, there wasn’t a convincing mechanism to link the physical act of holding your body upright with a positive and confident state of mind.
“Slowing your breathing is a free ticket to an altered state of consciousness”
Intriguing new research hints at an answer. Peter Strick at the University of Pittsburgh in Pennsylvania stumbled on a potential explanation while tracing neural pathways that connect the brain and the adrenal glands, which are located at the top of the kidneys and are responsible for the adrenaline rush caused by acute stress. Strick and his team found that the inner part of these glands, called the adrenal medulla, is linked to regions of the brain’s motor cortex, which controls voluntary movements. In turn, this neural pathway connects to the muscles of the core that stabilise the torso and support posture.
While it is too soon to be certain what information is being relayed along these routes, Strick thinks that the link could explain the stress-relieving effects of core-based exercise, such as Pilates, yoga and tai chi. Then again, all movement involves bracing the core to some extent. So however you choose to move, this pathway almost certainly comes into play at some point.
Stretching out stiff muscles feels good, but there seem to be some surprising additional benefits of loosening tight muscles. Emerging research suggests that stretching leads to changes in the fascia, sheets of connective tissue that wrap our muscles and allow them to slide over each other when we move.
Research by Helene Langevin, then at Harvard Medical School, found that stretching rat tissue causes cells within the fascia to release adenosine triphosphate. This molecule manages levels of inflammation, which is the immune system response that ramps up in times of stress or when we have an injury or infection. In a 2016 study, Langevin and her team injected carrageenan, a substance that causes local inflammation, into rats’ back muscles. Two days later, half of the rats were encouraged to stretch, while the other half weren’t. The rats that stretched not only had significantly lower levels of inflammation, but also higher levels of molecules that help resolve inflammation at the cellular level.
Other studies have found that the fascia are structured like a fluid-soaked sponge that drains into the lymphatic system. This could mean that stretching helps move the body’s fluids along, allowing the immune system to give these liquids a regular clean-out and deal with inflammation as it arises.
This matters for the mind because uncontrolled inflammation is linked to depression, chronic pain and fatigue. It is also exacerbated by modern lifestyles and obesity, and accelerates as we age.
Human studies into stretching and inflammation are still ongoing, but if it is confirmed that stretching and squeezing the fascia turns off inflammation after the threat has passed, it could help explain why people who do yoga and tai chi have lower levels of inflammatory markers in their blood. This could provide yet another reason to take regular breaks to stretch.