Former paratrooper Keith Abraham – who fought for the British military elite as part of The Parachute Regiment for nine years, serving in both Iraq and Afghanistan – made a surprise discovery while training for combat in 2002. His regiment was forced to complete endurance runs that involved each carrying 120lb (54kg) of cargo over 10-kilometer (6.2-mile) runs up very steep hills—a feat most of us would find tortuous, painful and genuinely misery-inducing. And probably impossible.
But for Abraham, who now runs the charity Heroic Hearts to provide support and therapy to veterans, that military training – and the endurance running in particular – was magic for his mind, allowing his brain to reach states of clarity and flow he never imagined possible.
“That level of extreme physical endurance is very hard to get into unless you’re forced to, and it’s profoundly extreme by anyone’s definition of extreme. But what that trained us to do was to allow our minds to just turn off,” he says. “Because in order to continue moving for such a long period of time while carrying so much weight, you have to just turn off your mind and focus on your breathing patterns and controlling your breath. And in that flow state, you can just keep going forever.”
Abraham had played plenty of sports since childhood, from rugby to football and downhill skiing. But counter-intuitively, it was only when preparing for war that his mind achieved so much peace.
“As a kid, sports were just an outlet for energy, as opposed to a way to achieve flow state. I didn’t have the presence of mind then to understand what I do now: that endurance exercise was a way to connect to my mind itself,” he says. “Increasingly, I came to understand that hard exercise wasn’t just a physical outlet, it was also about joy.”
I can relate. I also played a huge range of sports as a kid, and was especially passionate about baseball. I always got a kick out of nailing my pitches or smacking a home run. But in my late-teens, like many academically inclined folk, I abandoned sports because it required too much time, and I needed to focus on my studies.
Twenty years later, I was forced to rediscover the power of exercise, and of endurance cardio in particular, after a near-fatal house fire almost destroyed my flat and left me homeless for two months. The stress eviscerated me and I became depressed, which is not my normal state. Though the fire was behind me, all the switches in my brain had been thrown into a depressive state and I couldn’t turn them off. I was tired all the time. My writing suffered, and therefore so did my career and my finances. It was not a good time.
So I did what any sensible person would do: I joined a gym for the first time in my life, having been told it was the best thing to reboot my body and mind. For the first time, I got myself onto an exercise bike and an elliptical machine to sweat out the evil of two months of stress and insomnia.
Only then did I rediscover what I never should have forgotten: exercise is magic for the mind. After every workout, I not only felt more relaxed and upbeat – glowing with that “endorphin high”– but I also felt sharper and smarter. I could remember phone numbers and directions without effort. Boring paperwork and tiresome admin became a breeze. Skimming a pile of newspapers took no time at all. My career reached new heights. I’ve since adopted the habit of a good half hour of cardio when I need to think about a piece I’m writing – away from my desk with just my heartbeat and my breath to listen to, I find it much easier to generate new ideas or new ways to open a story.
Thing is, I never should have forgotten about the magic of movement. I was an athlete before I was a writer. But ever since that fire, I have never failed to go to the gym—even if I don’t feel like it. “This is more for my brain than it is for my body,” I remind myself, every time I am not in the mood.
“We’ve all had that experience of not wanting to hit the gym but then feeling like you have the blood of the gods running through your veins when you leave,” says Dr. Jaime Tartar, Neuroscience Program Director in the Department of Psychology and Neuroscience at Nova Southeastern University in Florida.
Dr. Tartar is also one of the founders of the Society for Neurosports, an interdisciplinary project that brings neuroscientists and exercise scientists together for a common goal: “To understand what is this phenomenon: why do we feel smarter, stronger, and just plain better with a bit of exercise?”
We’ve all heard of the “runner’s high” and the “endorphin rush” that gifts us the happy post-workout glow, but according to Tatar, there’s so much more to it than that.
“Exercise is the best way to stave off depression, improve cognition, decrease stress, dampen anxiety and protect against dementia,” she summarizes. “This is true for everyone, whether you’re an NFL player or the average person on the street. If we could sell the benefits of exercise in a bottle, everybody – everybody – would buy it.”
She’s right.
As soon as your heart starts pumping, it floods the brain with blood. Even gentle walking can boost blow flow by 15 percent by compressing the arteries and veins in your feet¹. This boost of blood brings with it nourishing hormones, neurotransmitters and other biochemicals: the messengers of the mind, which shuttle information between brain cells, allowing them to communicate and therefore function optimally.
You’ve heard of most of them: endorphins, which give us that famous rush. Endocannabinoids, our innate painkillers. Dopamine, the addictive pleasure chemical sparked by drugs, alcohol, gambling and other vices. Adrenaline (also known as cortisol), the “fight or flight” hormone which readies us for battle. Plus, to sweeten the deal: anti-inflammatory cytokines, which dampen systemic inflammation–increasingly implicated as a key component in depression.
Taken together, exercise is one hell of a drug. And like any good drug, the effects are felt immediately.
That rush of blood to the head is disproportionately channelled into the frontal cortex. This region, nicknamed the “CEO” or the “command and control center”, is one of the most recently evolved regions of the brain, generally associated with higher reasoning and cognition. Study after study³¯¹² has demonstrated that pumping blood, with its nourishing neurochemicals, into the frontal cortex induces immediate improvements in just about every measure of cognition or intelligence: memory recall, spatial reasoning, problem-solving, processing speed, focus, concentration, lateral thinking, creativity, and so much more.
That combination of elevated mood with an increased capacity to process complex information is what leads to another one of the magic tricks of exercise: alleviating anxiety and heightening resilience. “Exercise inoculates the brain against negative information,” summarizes Tartar.
Put another way, “Exercise gets all your nerve cells fired up and ready for grabbing what you can today,” says neuropsychiatrist Dr. John Ratey, Associate Clinical Professor of Psychiatry at Harvard Medical School, the author of 11 books and more than 60 peer-reviewed studies. He is widely regarded as one of the “elder statesmen” in the field, having pioneered the study of the cognitive benefits of exercise when few neuroscientists paid it much heed in the 1990s.
Though the long-term benefits of daily exercise – from cognitive improvements to a lowered risk of dementia – are clear, Dr. Ratey says that it’s more important that we think about exercise as “something you do for that day.”
“It gets you excited about being alive.”
Dopamine, endorphins, adrenaline, cytokines: that is one dense biochemical menu.
It’s crucial to note that the brain consumes 20 percent of our energy budget while only accounting for two percent of our body weight. It takes far more than its fair share, and there’s a reason for that. As legendary Ukrainian-American scientist Theodosius Dobzhansky famously put it in 1973: “Nothing in biology makes sense except in the light of evolution.”
“We see in the fossil record that when we became hunter-gatherers, the frontal cortex expanded with the addition of new nerve cells, precisely because we needed to track our movements,” explains Dr. Ratey. “We became more dexterous, we became more strategic, and we needed an improved capacity to focus.”
Which makes complete sense. Foraging over wide areas of terrain to feed an omnivorous diet required us to remember far more than our primate ancestors: which plants would nourish us, and which plants would kill us. Where they were located. When they were ripe to eat and when they were not.
Throw hunting into the mix – requiring the ability to track and predict the movement of prey, plus the ability to outsmart them – and it becomes even easier to understand how moving our bodies more drove the evolution of our brains (and not the other way round).
Traditional thinking held that our big, juicy brains predated our Olympian physiques, but new research has flipped that on its head: we needed larger brains because we were moving more. In other words, we would not have developed the capacity for calculus if we hadn’t been the original “gym monkeys”.
“There is a ‘bidirectional’ relationship between movement and brain health. If you want a healthy brain, you absolutely need a moving body,” says Dr. Tartar. “Many neuroscientists argue that the only reason animals have brains at all is because they move so much.”
Take tunicates, also known as sea squirts, she says. When afloat in the ocean, moving around, they carry primitive brains. But if they switch to a benthic form, stuck permanently to rocks, their bodies absorb and digest their precious brains, because the energetically expensive organ is no longer required.
We might be separated from sea squirts by several hundred million years of evolution, but we share 80 percent of our genes with them. Brain shrinkage from inactivity is therefore, unsurprisingly, also found in humans. A 2018 study¹³ in the highly regarded journal PLOS One – inoffensively titled “Sedentary behavior associated with reduced medial temporal lobe thickness in middle-aged and older adults” – found that inactivity correlated with a reduction in the size of the region of the brain that contains the hippocampus and amygdala, which are crucial for the formation and retention of memories.
The implications should give all of us pause for thought.
“I’m still shocked that most people know so little about the connection between physical fitness and mental acuity,” says Dr. Ratey. He chalks it all up to the rise of the internet and the modern focus on desk jobs. “It’s an incredible story, in a way, that we have ignored the needs of our bodies. We have gotten to the point that we are actually taught to ignore those needs.”
Exercise physiologist Sue Hitzmann, based in New York, frames it in even more stark terms:
“The most simplistic way to explain how exercise is so important for your brain is this: when you sit in a chair all day and don’t move, you are literally shrinking your brain,” she says.
The good news is you only need a moderate amount of exercise per day to ameliorate the deleterious impacts of inactivity, says Dr. Allison Brager, military scientist and the author of Meathead: Unraveling the Athletic Brain.
“You only need between 45 minutes and an hour per day – that’s the sweet spot that benefits your health, in every regard,” she says.
“Like many things in biology, there’s a ‘dose-response curve’,” says Brager. “If you exercise too little, the body’s response is negative. Too much, also negative. You just need a moderate and healthy balance to promote brain health.”
The benefits from moving our bodies are not simply felt during and after a workout, they accumulate over time. Practice might not make perfect, but repetition certainly reaps benefits. Every measure of human cognition, from long-term memory capacity to processing speed and problem-solving, has demonstrated that daily doses of exercise keeps brains plastic, young and healthy.
Again, we have neurotransmitters, hormones and other biochemicals – the postal workers of the mind – to thank for these benefits. Human growth hormone (HGH), which is integral to our development in puberty but drops off in our thirties, is boosted by daily movement. It keeps us young. The same goes for osteocalcin, the hormone responsible for reinforcing the integrity of our bones, something we all need as we age and become prone to accidents and falls. Irisin, nicknamed “the exercise hormone”, is also boosted by moving on a daily basis. Only recently discovered, its full benefits are yet to be revealed.
The most rigorously studied neurotransmitter demonstrated time and time again to induce measurable changes in brain anatomy and function: “Brain-Derived Neurotrophic Factor” (BDNF), which promotes “neurogenesis” (the formation of new brain cells) and “synaptogenesis” (the formation of new connections between brain cells). Think of BDNF as fertilizer for the brain, or as Dr. Ratey puts it: “Miracle-Gro for the mind.”
Outdated views held that we do not form new brain cells after adolescence, but nothing could be further from the truth. “If there is one thing I know about the brain, and what is fantastic about the brain, is how plastic it is,” says Hitzmann. “If you make exercise a habit, it will build new brain cells.”
And if you don’t make it a habit not only will you fail to make new brain cells, but you also increase your risk of Alzheimer’s, Parkinson’s, and other forms of neurodegeneration. In biology, to understand the function of something such as an organ or a gene you need to remove it from the system (such as a genetically modified mouse). And the same is true for exercise. The brain evolved to need daily physical movement and without that, it suffers.
It is estimated there are more than 57 million people worldwide today suffering from Alzheimer’s Disease¹⁴, predicted to number over 160 million by 2050.15 A ground-breaking 2011 study estimated that 13 percent of all cases of Alzheimer’s can be attributed to sedentary behavior, and that up to one million cases of this disease could be prevented with just a 25 percent decrease in our collective sedentary behavior¹⁵.
Simply put: sitting down is bad for us.
“It has become clear that physical activity is protective against neurodegenerative diseases. It helps us maintain our cognitive health,” says Dr. Art Kramer, Director of the Center for Cognitive and Brain Health and Professor of Psychology at Boston’s Northeastern University.
He speaks from a position of authority: Dr. Kramer published one of the earliest studies on the surprising cognitive benefits of exercise, nearly a quarter-century ago in 1999 in Nature¹⁶, one of the world’s top journals.
After providing 124 “previously sedentary” adults, aged 60 to 75, with one of two fitness prescriptions – aerobic exercise (walking) or anaerobic (stretching and toning) – he found the aerobic group improved in “executive control processes,” such as planning, scheduling, and working memory. But the anaerobic group did not¹⁷.
“Even in the elderly, aerobic exercise induces improvements in all cognitive aspects including memory, reasoning, problem-solving, and attention,” he says.
And gentle aerobic exercise is not only useful for maintaining our current state of cognition: it can improve it, even in our long-toothed years. His own research has shown that even small increases in physical activity can boost memory performance by up to 20 percent, no matter your age.*
With so many options on the table – running, walking, swimming, yoga, Zumba, boxing, high-intensity interval training (HIIT), CrossFit – how can anyone know what to choose for the best brain boost?
The answer is fairly simple: do what you like, and what comes naturally to you. Because if you enjoy it, you will continue to do it on a daily basis. “Just do whatever you will do,” summarizes Dr. Kramer.
If running is your physical drug of choice, evidence in both animals and humans shows us that it is physically good for our brains, and cognitively beneficial to our thinking. Rats put through exercises that mimicked going for a daily run experienced “neurogenesis” in their hippocampus¹⁸, which is crucial for the formation of memories.
Conducting similar experiments in humans has traditionally been next to impossible, as we cannot dissect a human brain to analyze cell structure right after a run. Thankfully, new imaging technologies allow us to see changes in the brain during and after running (previously tricky to measure due to the constant movement of our heads as we run – most studies on the cognitive benefits of cardio were therefore conducted on stationary cyclists). Another ground-breaking study published in Nature in 2021 demonstrated with near-infrared spectroscopy scans that running for just 10 minutes gives us a boost in blood flow to the prefrontal cortex (recall, the “CEO” of the brain) and improvements in “executive function” based on standard cognitive tests¹⁹.
If running isn’t your thing, or if you’re looking to vary your workouts, consider a team sport. Humans are social creatures, and any activity that requires us to coordinate with the movements of other people – from basketball to ballet and tennis – demands more from our brains than a solo activity.
“The secret to making your brain better is to stress it,” explains Dr. Ratey. “Which is why complex activities such as boxing and mixed martial arts can be surprisingly beneficial for the brain, as they require us to pay attention to multiple factors at the same time.”
According to Dr. Ratey, it is for this reason that neuroscientists recommend dance – and high-energy dance in particular – as the ultimate exercise for the frontal cortex.
“If your brain needs to coordinate physical actions in time to music – and pay attention to everyone around you – that’s quite a task,” says Dr. Ratey. Throw in the rush of endorphins, oxytocin, and dopamine from the pleasurable aspects of music, and that’s another neurological kick. “Just like martial arts, dancing demands you get the right form–you have to pay attention to so many things, and it’s incredibly complicated. That’s nothing but good for your brain.”
Which doesn’t surprise Professor Joe Verghese, Professor of Neurology & Medicine at the Albert Einstein College of Medicine, one bit. He has studied the cognitive benefits of dancing for nearly 20 years, after publishing a landmark study in the New England Journal of Medicine in 2003 on the surprising ways dancing is good for the brain²⁰. “Of 11 activities we studied, dance alone popped up as the one activity that was associated with a reduced risk of dementia,” he says.
“There are so many things going on at the same time: physical aspects, social aspects, creative aspects. All these things come together.”
This is uniquely challenging for the brain – and therefore uniquely good for the brain. “Because the best way to stress the brain as much as possible is to put multiple demands on it,” summarizes Dr. Ratey.
Given that the benefits of moving our bodies are rooted in biochemistry and biomechanics, could it be possible to hack the system? Could we gain the same benefits from a short but intense workout, such as HIIT?
Dr. Brager says that there is no need – pointing to the concept of “Non-Exercise Activity Thermogenesis”, or NEAT: we can gain as many benefits from gentle daily activities – such as gardening, taking the stairs, chasing our kids, walking to work, and more – as we can from an hour pumping iron. “All of it adds up. You don’t need to join a gym.”
But what if we could take – dare we ask – a pill?
“I don’t care what you think – no pill will ever recreate all those effects,” says Dr. Brager. She points to all the subtle but powerful impacts on our cells from just walking, such as the improvement in the “janitorial services” that glial cells perform, discarding cellular waste while we sleep. Or the singular ways that dance classes enrich the brain’s white matter – the high-speed highways of the mind²¹.
“Exercise also promotes the releases of neurotrophic factors from specialized organelles called exosomes, and that has impacts from skeletal muscles into the plasma and on to the brain,” argues Dr. Brager. “That cannot be replicated with a pill.”
I think Hitzmann put it far better than I ever could:
“Focusing on how the antidepressant effect of the ‘happy chemicals’ released by exercise gives you pleasure is missing the point,” she says. “The point is that exercise makes your brain more sensitive to all the joys that life can give you.”