Since working as a research fellow at Harvard in the 70s, John J. Ratey has been researching the brain-body connection. Spark is his way of checking in with the general public to share good news from the field of neuroscience about the amazing impact of exercise on brain development and the deterioration we suffer without it. Ratey argues that exercise is one of the best treatments out there for many of the issues we look to psychology to fix.

We are killing ourselves. When we sit in front of a computer all day at work and then return home only to stare at another screen, we go against the grain of nature. There is a mismatch between our sedentary lifestyle and what our genetics have equipped us to do. We humans are animals, and our species has been on the move for a couple million years. Modern technology and convenience have reached the point that our food moves to us rather than us moving toward it (and killing it and cooking it). This state of affairs is a relatively brief hiatus from the hunter-gatherer norm and high mobility our ancestors experienced.

Brain and body worked in tandem until recently. Now two-thirds of American adults are overweight and exercise is far from habitual for most. To add another layer of tragedy to it all, the modern story has not been one of the mental life triumphing at the expense of the body: Not only are our bodies breaking down without exercise, but our brains are deteriorating, too.

Our culture has been splitting apart body and brain, and the divorce has been hard on the kids (i.e., us, posterity). We need to reunite both aspects of personhood, and aerobic exercise is an excellent way to do so. Exercise strengthens the body and sharpens the mind, clears up mental fog, and gives us more energy. This isn’t just the “runner’s high” that outdoor enthusiasts relish. Exercise rewires the brain’s circuitry by slowing aging, catalyzing the brain’s learning processes, and attacking stress.

So if we want to save our bodies and brains, we need to recouple what was never meant to be separated.

Naperville, Illinois, gained national attention in 1999 when its students scored 6th in the word in math and 1st in science on the TIMSS (or Trends in International Mathematics and Science Study). This put Naperville ahead of China, Japan, and Singapore, which all routinely beat the United States. What made Naperville District 203 such an outstanding exception?

It all began when Naperville Central High converted its old cafeteria into a fitness center and offered students the opportunity to be guinea pigs in a fitness experiment. By giving students the opportunity to work out before classes (“Zero Hour,” they called it) students came into class ready to learn. Studies show this is not just a placebo. The students who went to reading class right after Zero Hour improved the most dramatically in reading. Their literacy scores were almost double that of students who slept in or took the standard gym class. The experiment was such a success that the school began rearranging students’ schedules so their hardest classes would be right after Zero Hour. The results were similarly impressive, and the initiative spread to the rest of the district.

Naperville’s initiative has made their students both healthier and smarter. Youth obesity rates there are a tenth the national average, and their standardized test scores are often significantly higher than national averages. These results are stunning and encouraging. With robust debate around the educational system and the best ways to help students who are often overweight and short on motivation, this is one of the most heartening findings in decades—precisely because it is easier to implement than many of the changes being debated.

Zero Hour offers students an experience very different from the gym classes of yesteryear. In Naperville, students aren’t just graded for showing up. They are graded for how long they spend in their target heart range. In other words, they have to stay active—active enough to bring up the heart rate to an aerobic level.

The Zero Hour model promotes fitness as a rhythm and lifestyle of working out—not just to pass a class but to have a pattern of life they can take with them into adulthood, one that will foster a happier and healthier and probably longer life. Traditional gym classes feature more team sports and competitions. The downside is that only 3 percent of adults continue to pursue team sports after age 24. The model fails to inculcate a lifestyle of fitness and training in the vast majority of students.

Naperville District 203's Zero Hour has been in place for years now and the district continues to rank in the top 10 districts in Illinois each year—even though Naperville’s schools have far less money per student than other school districts in the top 10. Education money per student is considered the best determinant of success, but Naperville found another, more economical way forward: fitness.

In the 21st century, most of us don’t regularly run from lions or fend off wolves like our ancestors did. The same mechanisms that trigger stress, however, still live in us even if they manifest themselves differently. If your boss yells at you, you probably won’t punch him in the face or run out of his office in a fit of terror. But that doesn’t mean you’re not stressed or that your body isn’t delivering adrenaline, tensing your muscles, or constricting your breathing. The instincts are all still there, operating before conscious thought. But you are not at the mercy of your body’s fear response. You actually have control over how stress impacts you.

The Department of Energy conducted an intriguing study in the 1980s—one they never published because the conclusion did not align with their hypothesis. They had two groups of shipyard workers in Baltimore, with tens of thousands in each group. All were engaged in the same kind of work. The sole difference was one group handled cargo that emitted very low levels of radiation. Researchers expected that exposure to radiation—even in trace amounts—would have deleterious effects on the workers’ health. Scientists were shocked to find that those exposed to radiation over years were healthier than those who were not. The mortality rate was 24 percent lower among those exposed to radiation. Massive amounts of radiation kills cells, but small doses invigorate them, making them tougher, much like immunization. 

This experiment with the dock workers gives us vital insight into the stress-recovery cycle in nature. The brain cells of those dock workers took the radiation as a challenge, and they were strengthened by the stress the radiation brought on. We see the same stress-recovery mechanisms at work in athletes, too. Muscles tear when people stress  them through exercise. As they rest, the muscles recover and grow stronger than they were. The same thing happens with how we process stress. Assuming the stress is not chronic and crippling, exposing ourselves to a moderate amount of stress and working through it is healthy, a fact that most modern de-stressing strategies tend to overlook.

We can think our way into a panic state simply by envisioning a stressful scenario. We can also, quite literally, run our way out of a panic. When we are stressed, the amygdala signals the adrenal glands in a hundredth of a second that it is time to release epinephrine, or adrenaline. Adrenaline coursing through our body triggers all kinds of physiological responses: Blood moves from the digestive tract to the arms and legs, the heart pumps harder, and we become hypervigilant. Endorphins reduce sensitivity to the sensation of pain. We are already primed to fight or flee—so why not just flee? Or at least go for a run.

When you exercise in response to stress, you are going with the physiological momentum your body just generated. Leaning into your biological cues is far healthier than sitting and stewing in your stress. All the energy built up from fight or flight responses that we curb in civilized society means we have to find other ways to release the pent up energy accruing in our bodies.

Stress and recovery happens in the brain just as it happens in the body. By exercising regularly, exposing your body to mild or moderate stress, you raise the threshold of what you think you can tolerate—mentally and physically.

On average, women spend between four days to a week out of every month or so in premenstrual syndrome or PMS, which adds up to about 9 years of pain and mood swings over the course of a lifetime. That’s a lot of life to spend in discomfort. Three out of four women report experiencing some kind of pain once a month. For 14 percent, the pain can be so severe that they skip class or call in sick. Thankfully, exercise can help.

The hormonal peaks and troughs throughout a woman’s life can be extreme. PMS floods the system with up to five times the usual supply of estrogen, and progesterone spikes, too. During pregnancy, the body releases 50 times the standard drip of estrogen, and 10 times the average flow of progesterone. Menopause is an extreme shift in the opposite direction, as progesterone and estrogen levels dwindle to very low levels.

A lot of women are already aware of the connection between exercise and reduced PMS-related pain. The research on this is not extensive compared to other body-brain repair research, but there is a Duke study that found women who exercised three times a week for an hour noticed improvements in 18 of 23 factors, including irritability, erratic action, and depression.

One popular myth surrounding pregnancy is that soon-to-be mothers should avoid exercise because the jostling will disturb the in-utero child, that rest and pausing exercise are best. But doctors are changing their tune. The American College of Obstetricians and Gynecologists (ACOG) recommends light to moderate exercise for pregnant women and those experiencing postpartum depression. It turns out staying sedentary, allowing stress and depression and all the related hormones to build up in the body, poses far bigger risks to the baby than exercise.

Much of what we know about how exercise alters the body and brain comes from studying depression. In England, exercise is the top recommendation medical professionals give to patients feeling down. In the United States, however, it’s not a common talking point in doctors offices. That advice would serve the US well because depression is the number one health concern, followed by cardiovascular disease and cancer.

Sadly suicide is prevalent in the United States, too: the country has a successful attempt every 17 minutes. Exercise is literally a lifeline for those struggling with depression. It could dramatically reduce those heartbreaking figures. Ratey defines depression as an “erosion of the connections in your life and between your brain cells.” Exercise can help repair both.

Study after study from the United States and Europe has found a negative correlation between exercise and depression. In other words, as regular exercise goes up, depression tends to go down. A Dutch study found people who exercised tended to be more outgoing and less neurotic and cynical. Another study found that serotonin, dopamine, and norepinephrine are produced in larger quantities when people exercise. These factors all help undercut depression, stabilizing mood, boosting motivation and satisfaction.  

Duke conducted a study in 1999 that discovered that regular exercise (three times a week for 30 minutes at 70-85 percent for this study) helped participants feel just as good as participants who were taking Zoloft. These findings corroborated a longstanding hunch that exercise was a viable alternative to meds for treating depression. The Duke study, now a landmark in the field, should be a wake up call for the entire medical industry, from medical students to practicing doctors to insurance companies to assisted living workers. Twenty percent of nursing home residents have depression. Just think of what an exercise regimen could do for the mental health of the elderly.

Blumenthal at Duke University followed up with students half a year after the study and discovered that only 30 percent of the exercise group were still depressed. From the group on meds, 52 percent were still depressed. In other words, in the long-term, exercise was more effective in treating depression than Zoloft. Interestingly, exercise also proves more effective than meds and exercise taken together.

The time element matters a lot when talking about depression and exercise. When people are depressed, they might feel happy for five minutes, but wonder if it will last. The struggle for hope intensifies when moments of hope last only a few minutes or hours. With prescription medication, you might feel relief in just a few days, but it might not deliver over the long-term. In the same way, if you go for only one run, you might feel depressed after the endorphins wear off post-exercise. But if you build up the habit, you give your brain a chance to transform itself to build more dopamine receptors. Those dopamine receptors help strengthen the association between aerobic exercise and reward.

There remains much to be learned about depression. We do not know depression’s biological origins, but we are measuring its symptoms with increasing clarity. PET scans and fMRI scans show us where they light up the brain—and where they tend to deplete it, like the prefrontal cortex and the hippocampus.

The results are in: If you want to improve your mental and physical resilience, exercise. Most programs recommend walking for 30 minutes a day, but studies find that aerobic exercise like running tends to beat stress, depression, and anxiety far faster. 

As one physiologist at Duke puts it, “A little is good, more is better.” He became an exercise guru hounded by journalists after his study found that even just three hours of walking a week improved cardiovascular function. He is modest in what he tells reporters as he does not want to make the threshold for jumpstarting a workout rhythm so high that people stop trying altogether. The main thing is to do something. You have to start somewhere.

What is the right amount of exercise for you? Everyone is different, but your best bet is to get fit and push that threshold of your aerobic ability. To ensure you are getting the intensity you need, find some way to monitor your heart rate. By running and building up endurance you are tapping into ancient rhythms. Our ancestors could run for days—literally. They would chase antelope for hours or days and eventually wear them out. Antelope rely on quick sprints to evade predators, but people are built for endurance, for the long game. Build up your endurance, keep running, and you’ll likely see your stress levels drop, your depression lift, and your mood stabilize.