This article is about how exercise affects the brain. It is not health advice. Before making any changes to your exercise routine, please consult your doctor and, if you’re under 18, your parents. Safety should always be your top priority.
Life Lessons From a Sea Squirt
The sea squirt is a strange animal. It is a marine invertebrate that spends most of its life stuck to a rock, eating whatever floats by. But young sea squirts are free-swimming creatures that look like tadpoles. They swim around, exploring and finding food until they’re old enough to settle down into their sedentary adult lifestyle. And this is where it gets weird: A free-swimming sea squirt larva has a primitive brain, but as soon as it settles down and attaches itself to a rock, the sea squirt eats its own brain!1
Human history parallels this process, though to a less extreme degree. Our hunter-gatherer ancestors were very active. They had to move all the time in order to stay alive. Later, when we became farmers and herders, most of us remained very active. But in recent decades, more and more people have taken desk jobs, and nearly all children spend huge portions of their time sitting in school. We now spend countless hours sitting in front of televisions and computer screens. And although our bodies have not dissolved and digested our brains as the sea squirts do, the sedentary lifestyle we now live is doing great harm to our brains.
“Paleolithic man had to walk five to ten miles on an average day, just to be able to eat. … Today, of course, there’s no need to forage and hunt to survive. Yet our genes are coded for this activity, and our brains are meant to direct it. Take that activity away, and you’re disrupting a delicate biological balance that has been fine-tuned over half a million years.”
–John J. Ratey, M.D.2
Stuart Brown, M.D., who wrote Play: How it Shapes the Brain, Opens the Imagination, and Invigorates the Soul, put it this way:
“When we stop playing, we stop developing, and when that happens, the laws of entropy take over—things fall apart. Ultimately, we share the fate of the sea squirt and become vegetative, staying in one spot, not fully interacting with the world, more plant than animal.”1
The Academic Benefits of Exercise
Researchers have repeatedly demonstrated that exercise improves cognitive performance. A 2018 meta-analysis of 26 academic studies which covered, in total, 10,000 students, found that “physical activity benefits learning in all academic subjects.”3 Exercise has also been shown to improve cognitive flexibility2 and enhance creativity,4 both of which are essential for academic success.
In one study, elementary school kids who were put on an exercise program saw academic performance jump by a whole grade level, that is, until the exercise program was taken away, at which point they reverted back to where they started.5 This shows that exercise gives us an immediate intelligence boost, but that we have to keep doing it to keep getting the benefits. And we should keep doing it for the long haul; exercise has long-term cognitive benefits and even helps prevent Alzheimer’s.5
Another reason to exercise is to increase your mental endurance. Most people’s performance declines throughout the day, whether it is a workday or a school day. But if you can get some exercise at some point during the day, you may be protected. When NASA gave their engineers an optional, mid-day exercise break and tracked everyone’s performance, it found that the exercisers had much better mental endurance than the non-exercisers.5
It gets even better. Executive function improves with physical activity,6 as does willpower.7 The meta-analysis found that exercise helps with “keeping kids on task and focused on their work.”3 It should come as no surprise then that regular exercise is one of the most effective interventions for ADHD, reducing symptoms of “impulsivity and inattention.”6 More broadly, recent research has shown that “kids with autism, attention deficit hyperactivity disorder and other brain-based conditions could stand the most to gain from boosting physical activity.”8
“To keep our brains at peak performance, our bodies need to work hard.” –John J. Ratey, M.D.2
Unfortunately, less than half of school-age children and teens get enough exercise!8 Part of the reason for this is surely that few people are aware of all these academic benefits. Everyone knows that exercise is a key part of physical health, but few people know how important it is for brain health. Please spread the word and lead by example.
So why does it help?
One reason exercise improves cognitive performance is that it increases blood flow to the brain, which has many positive effects, neatly summarized by Ivan Cavero Redondo, co-author of the 2018 meta-analysis mentioned above:
“‘Exercise influences the brain by increasing cerebral blood flow, which increases the supply of oxygen and nutrients and promotes blood capillaries’ formation, increases the neuronal connectivity through the promotion of the synaptogenesis and the availability of neurotransmitters.’”3
On the other hand, research from UCLA found that both lack of exercise and high blood pressure were associated with memory problems.9 And it has been suggested that clogged arteries will have a harder time delivering oxygen and nutrients to the brain, hurting cognitive function.10
The brain is constantly growing new connections as we learn – a rewiring process called neuroplasticity – and it is constantly growing new neurons – a process known as neurogenesis. Exercise promotes both of these brain-changing functions.11, 2 This should not only make learning easier, but also behavioral change and habit formation.
Mental Health Benefits
Another reason exercise benefits students academically is that it benefits them emotionally.
School is demanding and stressful. Teen and preteen life can be very socially stressful. And while it is possible to have a healthy, even helpful response to stress,12 stress often makes people feel worse and perform poorly. Exercise provides a physiological release for stressful energy, and it improves the way the body and brain respond to stress.13 Exercise reduces levels of the stress hormone cortisol, and can even help with clinical anxiety.14 Exercise also leads to better sleep,14 which is critical for stress recovery15 and memory formation.4
“Just keep in mind that the more stress you have, the more your body needs to move to keep your brain running smoothly.” –John J. Ratey, M.D.2
(Note: exercise is just one component of strategic stress-management.)
Exercise also makes you happier,2 and happiness improves cognitive performance.16 Exercise improves levels of endorphins, norepinephrine, and serotonin, all of which improve mood.14 In fact, exercising can give you a 12-hour mood boost, so getting in a morning workout can improve your mood all day.17 This isn’t just a good thing because it feels better to be in a better mood, it’s also a good thing because improving your mood increases your intelligence, creativity, motivation, and productivity.16 This is the biggest reason why exercise is part of my morning routine.
Meanwhile, depression makes it more difficult to do everything, including schoolwork.16 Plus, depression is linked to memory problems.9
Longitudinal research done over many years shows that exercise prevents depression, so it’s wise to exercise regularly to protect yourself from getting depressed.2 Or if you’re already depressed, you should know that research shows exercise to be an effective treatment for depression, on par with the best antidepressant medications available.2 Exercise also helps teens feel better about their bodies and have improved overall self-esteem.14 Exercise is certainly not the only thing you should do to prevent or treat depression, but it’s an important part of the puzzle.
And really, since exercise is what our ancestors did all the time, it’s our baseline state of existence. When we stop exercising, we fall below our baseline level of happiness and mental health. Or, as former Harvard professor Tal Ben-Shahar put it, “Not exercising is like taking a depressant.”15
Teens who exercise are less likely to develop substance abuse disorders, and drug addicts are more likely to recover if exercise is part of their treatment program.14 I wouldn’t be at all surprised if it helps with video-game addiction too. At the very least, getting outside to run around and play gets you away from screens for a while, which is something we all need.
How much exercise does it take?
It depends who you ask. Some experts say that “teens who do some sort of physical activity three to five times a week, for at least 30 minutes, can reap mental health benefits.”14 While John J. Ratey, M.D., author of Spark: The Revolutionary New Science of Exercise and the Brain, calls on people to do more than that:
“The best, … based on everything I’ve read and seen, would be to do some form of aerobic activity six days a week, for forty-five minutes to an hour. Four of those days should be on the longer side, at moderate intensity, and two on the shorter side, at high intensity. … In total, I’m talking about committing six hours a week to your brain. That works out to 5 percent of your waking hours.”2
But, Ratey also says that just doing something, anything, is what’s most important.2 Just get started. We have to remember that everything counts, and perfectionism isn’t helpful. Any exercise is better than none. 5 minutes is much better than 0 minutes. 10 minutes is better than 5 minutes. 20 minutes is better than 10 minutes.
But this pattern doesn’t continue forever. If you get too much, you’ll wear yourself out and just want to sleep. An all-day hike or a 90 minute run might drain you of so much physical energy that your mind will feel tired too. It’s not that you should never get that much exercise in a day, just maybe not before you have studying to do or an exam to take.
And for safety’s sake, don’t overdo it. It’s better to do too little than too much, especially at first. If you haven’t been exercising regularly, ease into it by doing little bits, giving yourself time to rest and recover. Remember, if you push it too hard and get hurt, you won’t be able to exercise at all. Ratey says, “If you haven’t been active, I think the best way to begin is to start walking. Take the stairs instead of the elevator, park at the back of the lot, and go for a stroll around the block at lunchtime.”2
What type of exercise is best?
Although most of the research looks at aerobic exercise – running, hiking, biking, swimming – any kind of exercise is likely be beneficial. Play sports, go rock climbing, do yoga – whatever you like. If you enjoy it, you’ll probably do it more and therefore get more benefit. You’ll also exercise more often if you apply The 20-Second Rule and make it more convenient to work out.
And when in doubt, mix it up. Some research shows that your brain gets a larger benefit from doing a variety of exercises.5 Ratey agrees:
“And while there’s conflicting evidence about whether high-intensity activity, which can force your body into anaerobic metabolism, impacts thinking and mood, it clearly releases some of the important growth factors from the body that build up the brain. So, on the shorter, high-intensity days, include some form of strength or resistance training. These days should not be back to back; your body and brain need recovery time to grow after high-intensity days.”2
Not sure where to start? No gym membership? No problem. Groomandstyle.com created this excellent run-down of the many, many great ways to exercise without going to the gym.
If exercise can also incorporate some sort of play, then you’ll be getting all the additional benefits associated with play, not to mention having fun.
And if exercise is done in nature, such as hiking, this comes with bonus benefits as well. Ratey calls exercise done in nature “exercise squared.”2
But please no brain injuries! Please choose sports that don’t usually lead to concussions. I know this is radical to say, but brain damage does not make you smarter. Tackle football and heading soccer balls* are both known to cause brain damage.18, 19 Wear helmets when biking, climbing, skiing, or doing any other sport where your head is at risk. Protect your brain – it’s the only one you get!
*You can play soccer without heading the ball.
Movement matters too.
Returning to the idea that we live radically sedentary lives compared to our ancestors, it’s essential that we not only embrace exercise, but movement more broadly.
It’s possible to get in a serious workout, and then be sedentary for the rest of the day, and unfortunately, the workout doesn’t fully offset the harmful effects of not moving for most of the day.20 Indeed, research from UCLA showed that even if you exercise regularly, too much sitting can still harm the brain.21
Joan Vernikos, author of Sitting Kills, Moving Heals, suggests that we seek out “opportunities to move,” also known as OTMs, such as taking the stairs, standing up frequently from our desk, and parking farther away from the grocery store.20 The next time you have ten minutes to kill, consider putting your phone away and going for a short walk. Find as many OTMs as you can, take advantage of them, and be proud of yourself for doing so.
“From your genes to your emotions, your body and brain are dying to embrace the physical life. You are built to move.” –John J. Ratey, M.D.2
Movement and exercise are built into human nature. The human mind expects you to move your body, and it will reward you if you do.
Chris Loper has been an academic coach for Northwest Educational Services since 2014.
Chris also offers habit coaching, helping busy adults with habit formation and productivity.
In 2021, he published a humorous memoir titled Wood Floats and Other Brilliant Observations, a book that blends crazy stories with practical life lessons, available on Amazon and through most local bookstores.
He lives in Issaquah, WA, where he is the owner of South Cove Tutoring.
1 Brown, Stuart, M.D. and Christopher Vaughan. Play: How It Shapes the Brain, Opens the Imagination, and Invigorates the Soul. Avery, 2010.
2 Ratey, John J., M.D. Spark: The Revolutionary New Science of Exercise and the Brain. Little, Brown & Company, 2008.
3 Reuters. “Active children may also excel in school.” The Straits Times. April 8, 2018.
4 Oakley, Barbara. A Mind for Numbers: How to Excel at Math and Science (Even if you Flunked Algebra). Penguin, 2014.
5 Medina, John. Brain Rules: 12 Principles for Surviving and Thriving at Work, Home, and School. Pear Press, 2008.
6 Reynolds, Jennifer Lea. “Can Sports Help Kids Manage Their ADHD Symptoms?” US News & World Report. July 31, 2017.
7 Halvorson, Heidi Grant. Succeed: How We Can Reach Our Goals. Plume, 2011.
8 Szklarski, Cassandra. “Study says exercise fosters brain health for kids with autism, ADHD.” The Canadian Press. June 19, 2018.
9 University of California, Los Angeles. “Poor health, lifestyle factors linked to memory complaints, even among younger adults.” Medical Xpress. June 4, 2014.
10 Hospital, Craig. “Exercise and Your Brain.”
11 Perlmutter, David, MD. “Neurogenesis: How to Change Your Brain.” The Huffington Post. November 2, 2010.
12 McGonigal, Kelly. The Upside of Stress: Why Stress Is Good for You, and How to Get Good at It. Avery, 2015.
13 “Exercise fuels the brain’s stress buffers.” American Psychological Association.
14 Monroe, Jamison Jr. “Get Moving: The Benefits of Exercise for Teen Mental Health.” US News & World Report. May 28, 2018.
15 Ben-Shahar, Tal. Psychology 1504: Positive Psychology. Harvard Open Course, 2009.
16 Achor, Shawn. The Happiness Advantage: The Seven Principles of Positive Psychology That Fuel Success and Performance at Work. Crown Business, 2010.
17 Rath, Tom. Eat Move Sleep: How Small Choices Lead to Big Changes. Missionday, 2013.
18 Radiological Society of North America. “Brain impact of youth football: Brain changes after one season of play.” Science Daily. November 27, 2017.
19 Nutt, Amy Ellis. “Heading a soccer ball causes instant brain changes, study finds.” The Washington Post. October 25, 2016.
20 Vernikos, Joan. Sitting Kills, Moving Heals: How Everyday Movement Will Prevent Pain, Illness, and Early Death — and Exercise Alone Won’t. Quill Driver Books, 2011.
21 Walton, Alice G. “Too Much Sitting Is As Bad For The Brain As It Is For The Body: Study.” Forbes. April 12, 2018.