Spark: The Revolutionary New Science of Exercise and the Brain

by John J. Ratey

head comparison until researchers at Duke University took up the task in 1999. In a landmark study affectionately called SMILE (Standard Medical Intervention and Long-term Exercise), James Blumenthal and his colleagues pitted exercise against the SSRI sertraline (Zoloft) in a sixteen-week trial. They randomly divided 156 patients into three groups: Zoloft, exercise, or a combination of the two. The exercise group was assigned to supervised walking or jogging, at 70 to 85 percent of their aerobic capacity, for thirty minutes (not including a ten-minute warm-up and a five-minute cool-down) three times a week. The results? All three groups showed a significant drop in depression, and about half of each group was completely out of the woods—in remission. Another 13 percent experienced fewer symptoms but didn’t fully recover.

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About 30 percent of the exercise group remained depressed versus 52 percent of those on medication and 55 percent for those in the combined treatment group.

And of the patients who were in remission after the initial study, just 8 percent of the exercise group had a relapse versus 38 percent in the medication group—quite a significant difference.

Specifically, every fifty minutes of weekly exercise correlated to a 50 percent drop in the odds of being depressed.

it was only after she started a family that she fell out of the habit of exercise. “I just got too busy and forgot the benefits of working out,” she says. “Now I feel like I have my brain back.”

She also found evidence that the degree of shrinkage was directly related to the length of depression, and this was news. It might explain why so many patients with depression complain of learning and memory trouble, and why mood deteriorates in Alzheimer’s, the neurodegenerative disease that begins with erosion of the hippocampus.

With cognitive behavioral therapy and psychotherapy, we feel better about ourselves before we feel better physically. Therapy works from the prefrontal cortex down, to modify our thinking so we can challenge the learned helplessness and spring ourselves out of the hopeless spiral.

The high-intensity groups burned an average of 1,400 calories (eight calories per pound) during the course of either three or five sessions per week. At the end of three months, regardless of frequency, the high-intensity groups cut their depression scores in half.

If you weigh 150 pounds, that would translate into about three hours at moderate intensity per week.

Just multiply your body weight by eight to figure out how much you should be burning for the high dose, and then head to the gym to find out how many calories you burn during a given workout (most of the aerobic machines track this for you). If you weigh 150 pounds and burn 200 calories in thirty minutes on the elliptical trainer, you’d want to do six sessions a week to meet the high dose.

But the glitch in the attention system isn’t strictly a deficit—it’s more of an inability to direct attention or to focus on command. I tell my patients a more helpful way to think of ADHD is as an attention variability disorder; the deficit is one of consistency.

One of the classic signs is the pirouette: stepping out the door, the ADHD patient will spin around and go back upstairs to get something she forgot. Everyone does this, of course, but for some of my patients it’s a daily occurrence.

the amygdala is responsible for assigning emotional intensity to incoming stimuli before we’re conscious of it, and then sends it along for higher processing. In the context of ADHD, the amygdala determines the “noticeableness” of things. An unregulated amygdala is what feeds the tantrums or blind aggression in patients with ADHD, and their oversensitivity to excitement can lead to panic attacks. Sometimes excitability is a positive—people with ADHD can get so enthusiastic about something that they energize a roomful of people. (Holding the attention of others is no problem for those with ADHD.)

We can think of inattention in general as an inability to inhibit interest in unimportant stimuli and motor impulses.

The prefrontal cortex is also the home of working memory, which sustains attention during a delay for a reward, and holds multiple issues in the mind at once. If working memory is impaired, we can’t stay on task or work toward a long-term goal because we can’t keep an idea in mind long enough to operate on it or to ponder, process, sequence, plan, rehearse, and evaluate consequences. Working memory, which is like our random-access memory (RAM), can be considered the backbone of all the executive functions. A failure of working memory is also why people with ADHD are terrible at keeping track of time and thus prone to procrastination.

That’s also when he noticed the symptoms of what we would agree was ADHD. He explained that he would have a tantrum if his girlfriend interrupted his writing, or yank the phone out of the wall if it rang while he was trying to concentrate. He was slipping out of touch with his friends. He fit the profile, and we decided to put him on ADHD medication, which helped.

Driven to Distraction.

The best strategy is to exercise in the morning, and then take the medication about an hour later, which is generally when the immediate focusing effects of exercise begin to wear off. For a number of patients, I find that if they exercise daily, they need a lower dose of stimulant.

general, I tell my patients to make every effort to institute a regimen of daily exercise—or at least during the five weekdays, when they need to focus at school or work. Dishman’s study suggests that submaximal exercise, which would be 65 to 75 percent of maximum heart rate, is more effective with girls, while more vigorous exercise (just below the anaerobic threshold, which I’ll explain in chapter 10) works better for boys. We don’t really have parallel data for adults, but from what I’ve seen, it’s important to get the heart rate up there—maybe 75 percent of your maximum for twenty or thirty minutes.

(14 percent miss school or work at some point because of PMS). Every month since she was about sixteen, if she doesn’t exercise Patty gets tired, irritable, itchy, anxious, agitated, and aggressive in the days leading up to her period. She has difficulty focusing; she tosses and turns at night; and she craves carbohydrates. Her ankles and belly swell; her face develops a rash; she gets constipated; and her breasts hurt. “That’s when I really push myself,” she says. “The week before my period I have to do an hour of cardio four days a week or I can’t stand myself.” She learned early on that aerobic exercise dramatically dials back her symptoms.

It’s impossible to say where the gap is in Patty’s brain chemistry, for example, but there’s no question that exercise helps close it. “It’s almost like I’m in a fog before my period,” she says. “I could take my ADHD medication, and it won’t do a damn thing. Exercise helps clear my head.”

Many women already know this: one survey of more than eighteen hundred women found that at least half of them use exercise to alleviate the symptoms of PMS. In addition to reporting less physical pain, the women who exercise scored better on evaluations of concentration, mood, and erratic behavior.

Each group trained for an hour three times a week. The twelve aerobic women did thirty minutes of running at 70 to 85 percent of their aerobic capacity, along with a fifteen minute warm-up and cool-down. The other eleven used weight machines for supervised strength training. Both groups’ physical symptoms improved, but the runners improved significantly more on the mental side. They felt better on eighteen of twenty-three measures, the most significant of which were depression, irritability, and concentration.

You start to lose track of the events that have shaped who you are, which is a terribly threatening feeling that eats away at your sense of self. A lot of people who find themselves in this position tend to retreat, unknowingly mirroring their dendrites. They don’t venture out and make new connections for fear that they won’t know how to react, and they withdraw from the world, either out of embarrassment or simply because they feel uncomfortable outside the familiarity of home. Either way, the result is that they get cut off from meaningful relationships, which are an important form of stimulation for the brain. Isolation and inactivity feed the cellular death spiral,

test for the disease is to show someone a list of words and ask what she can recall half an hour later.

The major implication is that exercise not only keeps the brain from rotting, but it also reverses the cell deterioration associated with aging.

would recommend 1000 IU (international units) of vitamin D and for women, 1500 mg of calcium. I would also recommend taking vitamin B with at least 800 mg of folate, which improves memory and processing speed.

AEROBIC. Exercise four days a week, varying from thirty minutes to an hour, at 60 to 65 percent of your maximum heart rate.

Try a more intense pace for two days a week—70 to 75 percent of your maximum—for twenty to thirty minutes.

STRENGTH. Hit the weights or resistance machines twice a week, doing three sets of your exercises at weights that allows you to do ten to fifteen repetitions in each set.

tennis, dancing, aerobics class, jumping rope, basketball, and, of course, running.

BALANCE AND FLEXIBILITY. Focus on these abilities twice a week for thirty minutes or so. Yoga, Pilates, tai chi, martial arts, and dance all involve these skills, which are important to staying agile.

Volunteering is beneficial because it involves social contact, which is inherently challenging for the brain. Anything that keeps you in contact with other people helps you live better and longer—statistics show a tight inverse relationship between sociability and mortality. Novel experiences demand more from your brain, and this builds its ability to compensate. You get more Miracle-Gro, more connections, more neurons, and more possibilities.

low-intensity (walking), moderate-intensity (jogging), and high-intensity (running) exercise. If you want to make the most of your time and effort, you’ll need a way to accurately judge your level of exertion along these divisions. When I talk about walking, or low-intensity exercise, I’m referring specifically to exercising at 55 to 65 percent of your maximum heart rate. By my definition, moderate intensity falls in the range of 65 to 75 percent, while high intensity is 75 to 90 percent. The upper end of high-intensity exercise is sometimes painful but always powerful territory that has gained a lot of scientific interest recently.

The best, however, 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. 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;

Normally HGH stays in the bloodstream only a few minutes, but a session of sprinting can keep the level elevated for up to four hours. In

One factor clearly affected by strength training is HGH. A recent study looked at the hormone levels during weight training versus aerobic activity in well-trained men. Doing squats doubled HGH levels compared with running at high intensity for thirty minutes, and I think this will turn out to have important implications for exercise recommendations.

yogic breathing reduces stress and anxiety levels, and tai chi reduces the activity of the sympathetic nervous system (judging from heart rate and blood pressure). One recent study used MRI scans on eight yoga practitioners and found that their levels of the neurotransmitter gamma-aminobutyric acid (GABA) increased 27 percent after a sixty-minute session. GABA is the target of Xanax-like drugs and is very involved with anxiety, so this may be part of the reason why yoga helps some people relax. Much of the evidence from this realm is anecdotal, but I’m sure that as neuroscientists delve deeper into the brain they’ll discover pathways that connect the dots.