Exercise does more than build muscles andhelp prevent heart disease. New science showsthat it also boosts brainpower-and may offerhope in the battle against Alzheimer's.

BY MARY CARMICHAELHE STEREOTYPE OF THE "DUMB JOCK' HAS NEVERsounded right to Charles Hillman. A jock himself, heplays hockey four times a week, but when he isn'tbody-checking his opponents on the ice, he's givinghis mind a comparable workout in his neuroscienceand kinesiology lab at the University of Illinois. Nearly

every semester in his classroom, he says, students on the women'scross-country team set the curve on his exams. So recently hestarted wondering if there was a vital and overlooked link betweenbrawn and brains-if long hours at the gym could somehowbuild up not just muscles, but minds. WIdI colleagues, he roundedup 259 Illinois third and fifdI graders, measured their body-mass index and put them dIrough classic PE routines: dIe "sit-and-reach;' a brisk run and timed push-ups and sit-ups. Then hechecked their physical abilities against their math and readingscores on a statewide standardized test. Sure enough, on dIe whole,

38 NEWSWEEK MARCH 26. 2007

exercise are far more pro-

found and complex than

they once thought. The

process starts in the mus-

cles. Every time a bicep or

quad contracts and re-

leases, it sends out chemi-

cals, including a protein

called IGF-I that travels

through the bloodstream,

across the blood-brain bar-

rier and into the brain it-

self: There, IGF-I takes

on the role of foreman in

the body's neurotransmit-

ter factory. It issues orders

to ramp up production of

several chemicals, includ-

ing one called brain-

derived neurotrophic fac-

tor, or BDNF. Ratey, author

of the upcoming book

"Spark: The Revolutionary

New Science of Exercise

and the Brain:' calls this

molecule "Miracle-Gro for

the brain:' It fuels almost

all the activities that lead

to higher thought.

With regular exercise,

the body builds up its lev-

els of BDNF, and the

brain's nerve cells start to

branch out, join together

and communicate with

each other in new ways.

This is the process that

underlies learning: every

change in the junctions

between brain cells signi-

fies a new fact or skill that's been picked

up and stowed away for future use.

BDNF makes that process possible.

Brains with more of it have a greater ca-

pacity for knowledge. On the other

hand, says UCLA neuroscientist Fernan-

do G6mez- Pinilla, a brain that's low on

BDNF shuts itself off to new informa-

tion. In his experiments, rats were put

through weeks of running on a wheel,

a workout that increased their BDNF

levels. G6mez-Pinilla left half of the

animals alone; in the other half, he

blocked the chemical's effects with a

I( (m) )) For more wellness coverage, read To, ~ Yo-Ur&alfuat xtra.Newsweek.c:mD-

the kids with the fittest bod-ies were the ones with thefittest brains, even whenfactors such as socioeco-nomic status were taken in-to account.Sports, Hillmanconcluded,might indeed beboosting the students' intel-lect-and also, as long as hedidn't "take a puck to thehead," his own.

Hillman's study, whichwill be published later thisyear, isn't definitive enoughto stand alone. But itdoesn't have to: it's part ofa recent and rapidly grow-ing movement in scienceshowing that exercise canmake people smarter. Lastweek, in a landmark pa-per, researchers announcedthat they had coaxed thehuman brain into growingnew nerve cells, a processthat for decades had beenthought impossible, sim-ply by putting subjects ona three-month aerobic-workout regimen. Otherscientists have found thatvigorous exercise cancause older nerve cells toform dense, interconnect-ed webs that make thebrain run faster and moreefficiently. And there areclues that physical activitycan stave off the begin-nings of Alzheimer's dis-ease, ADHD and other cognitive disor-ders. No matter your age, it seems, astrong, active body is crucial for buildinga strong, active mind.

CIENTISTS HAVE ALWAYS SUS-as much, although they

have not been able to proveThe idea of the "scholar-

athlete" isn't just a marketingploy dreamed up by the NCAA; it goesback to the culture of ancient Greece, inwhich "fitness was almost as importantas learning itself," says Harvard psychia-trist John Ratey. The Greeks, he adds,were clued into "the mind-body connec-tion." And they probably intuited a basic

principle

that Western researchers alsofigured out long ago: aerobic exercisehelps

the heart pump more blood to thebrain, along with the rest of the body.More

blood means more oxygen, andthus better-nourished brain cells. For

decades, that has been the only link be-tween athletic and mental prowess thatscience has been able to demonstratewith any degree of certainty. "Peoplehave

been slow to grasp that exercise canreally affect cognition," says Hillman,'~ust as it affects muscles:'

Now, however, armed with brain-scanning tools and a sophisticated un-derstanding of biochemistry, researchersare realizing that the mental effects of

40 NEWSWEEK MARCH 26. 2007

BLOOD VOLUME IN THE BRAIN: NEUTRAL INCREASED

Gage's experiment, the new neurons cre-ated by exercise cropped up in only oneplace: the dentate gyrus of the hip-pocampus, an area that controls learn-ing and memory. This region, tuckedunder the temporal lobes, helps thebrain match names to faces-one of thefirst skills to erode as we age. Fortunate-ly, the hippocampus is especially re-sponsive to BDNF's effects, and exerciseseems to restore it to a healthier,"younger" state. "It's not just a matter ofslowing down the aging process," saysArthur Kramer, a psychologist at theUniversity of Illinois. "It's a matter ofre-versing it." Kramer's work also has im-plications for the frontal lobes, the seatof "executive functioning"-a type ofhigher thought that entails decision-making, multitasking and planningahead. With scanning technology, hehas found that exercise causes thefrontal lobes to increase in size. Andin dozens of previous studies of menand women in their 60s and 70s, brisk

THE EVIDENCE: Whennew nerve cells form inthe brain, their growthis accompanied by thecreation of blood vessels.

Researchers found that exercise increasedblood volume in the dentate gyrus (a region ofthe hippocampus, which is used in memory),implying new cells were forming in the area.

SOURCES NATIONAL ACAOEMY OF SCIENCES OFTNE USA, COLUMBIA UNIVERSITY

Relative blood volume inthe brain with exercise

2.0 Af!er

1.5IBefore

1.0 exe~cise!

0.5 i

0 JIDENTATE GYRUS

-MARC BAIN

111.1

NUKE NJf.URUGJf.NESIS WHICH,can take weeks to occur, mostof these additional effects ap-pear almost immediately. Getoff the treadmill after a half-

hour workout, says Hillman, and "within48 minutes" your brain will be in bettershape. But alas, these benefits are some-what transient. Like weight, mental fit-ness has to be maintained. New neurons,

II:

drug. Then he subjectedboth groups of athleticrats to a test of wits, en-couraging them to find anobject that was hidden un-derwater. The first groupeasily pinpointed its loca-tion, but the second, BDNF-deprived group wasn't near-ly as quick or sharp.Nature has conducted asimilar experiment on hu-mans. In unlucky peoplewith a faulty variant of thegene that makes BDNF,the brain has trouble bothcreating new memories andcalling up old ones.

Most people maintainfairly constant levels ofBDNF in adulthood. But asthey age, their individualneurons slowly start to dieoft: Until the mid-'90s, sci-entists thought the loss waspermanent-that the braincouldn't make new nervecells to replace the deadones. But animal studiesover the last decade haveoverturned that assump-tion, showing that "neuro-genesis" in some parts of the brain can beinduced easily with exercise. Last week'sstudy, published in the Proceedings ofthe National Academy of Sciences, ex-tended that principle to humans for thefirst time. After working out for threemonths, all the subjects appeared tosprout new neurons; those who gainedthe most in cardiovascular fitness alsogrew the most nerve cells. This, too,might be BDNF at work, transformingstem cells into full-grown, functionalneurons. "It was extremely exciting to seethis

exercise effect in humans for the firsttime," says Scott Small, a Columbia Uni-

versity Medical Center neurologist whocoauthored the study with Salk Instituteneurobiologist Fred Gage. "In terms oftrying

to understand what it means, thefield is just exploding."

The first step toward that under-standing is to figure out exactly wherethe new brain cells are growing-andwhether that is a part of the brain thatneeds to be rejuvenated. In Small and

MARCH 26, 2007 NEWSWEEK 43

walking and other aero-bic workouts have yieldedimprovements in execu-tive functioning. Subjectshave fared better on psy-chological tests, answer-ing questions more accu-rately and quickly. Withthe new brain studies, re-searchers can now beginto explain why.

As far as scientists know,new neurons can't growthroughout the rest of thebrain. But other regionsbenefit from exercise inmany secondary ways.Blood volume, like brainvolume, increases with ex-ercise, says Small: "Wher-ever you have the birth ofnew brain cells, you havethe birth of new capillar-ies." Active adults haveless inflammation in thebrain. They also have few-er "little bitty strokes thatcan impair cognitionwithout the person evenknowing," says Universityof California, San Francis-co, neuroscientist Kristine

Yaffe. Still other researchers have foundthat athletes have more astrocytes, orcells that support neurons and mop upneurotransmitters after they're used tosend messages from cell to cell. Andeven the levels of those neurotrans-mitters are higher in people who exercisefrequently. "Dopamine, serotonin, nor-epinephrine-all of these are elevatedafter a bout of exercise," says Ratey. "Sohaving a workout will help with focus,calming down, impulsivity-it's liketaking a little bit of Prozac and a littlebit of Ritalin."

r ~ ~--

For!

brainsome

.be-stick, but

and

thetween 1around for

ity,"(

.down again, and then theneurons don't function aswell anymore," says Wil-liam Greenough, a psy'

~

of Illinois. bod;go, then, 'i brainwill follow.

Th keep the effects,you've got to keep work'-ing out. "If you're think-ing that by exercising: at,age 20' ,

have someyou're likeGreenoughbetter bemit to 50ting the r

~

what70",

hit-

kid.is,

have

just

focused

onthe folks

minds

aused to be-!

_r- ., i

they

bi.

group atyoung ('even morecise J " ,

fect onsays ]"

in

don't have fully developed frontal lobes,so they "recruit" other parts of the brainto perform necessary functions, includ-ing those involved in learning. In Hill-man's look at third- and fifth-grade PEstudents, exercise sped up not just exec-utive functioning, but a broad variety ofskills ranging from math to logic toreading, all of which rope in many re-gions of the brain. "In kids you have atremendous amount of growing braintissue, particularly in the frontal lobe,"says Thmporowski. "So we can't justbreak it down to hippocampal func-tion in them. Exactly what else is go-ing on in there, I don't think any-body knows."

Exer-more long-lasting ef-

are still developing,"T -r r

In kids, asreaps manywon't (: .ADHD

r ~,

Gal activity ;~ "'for drugs. In ':

, the hippocampusfrom exercise. This

.of kids with

or supplementwith the disorder,, 'and it may

.in abnor-

mal

ways that affect its function.But a good workout, or for that mat-

ter a boisterous session of kickball, canalso have much more widespread effectson children's brains. Until about 20, kids

With that science inmind, many educatorsare now pushing foran overhaul of physicaleducation in publicschools. Teachers canensure their students'success in other sub-jects, they argue, bymaking PE longer andmore focused on brain-strengthening cardiovas-cular exercise. Inspiredby Hillman's work, Ken-tucky state Sen. KatieStine recently proposeda bill making a daily halfhour of PE mandatoryfor kids up to eighthgrade. It passed the Sen-ate last month. And atschools in Naperville,111., students with poorverbal skills have startedtaking PE immediatelybefore reading class.Their report cards, saysRatey, are already look-ing better.

The hope of educa-tors isn't just that John-ny and Susie will do bet-ter on the SAT. There's along-term goal as well. Ifkids develop a love ofsport early in life, they'remore likely to grow intoactive adults. And if theydo, they may avoid a fatetheir grandparents are

currently facing: a slow slide into mildcognitive impairment, followed byAlzheimer's. GOmez- Pinilla says thatAmericans' lazy lifestyles may be con-tributing to their high rates of the dis-ease. Humans have evolved, he notes, tothrive on physical activity; without it,"our brains aren't doing what they'resupposed to," and they go awry. Earlystudies suggest that people who exer-cise at least a few times a week tend todevelop Alzheimer's less often and laterthan their more sedentary counterparts.There are clues at the level of the brainas well: one of the disease's first targetsis the hippocampus.

More controversial is the proposal

44 N EWSWE EK MARCH 26. 2007

"~ " 'lonc-lasting ways-which is why

are lobbYing for more time in PE class.

Fitness." So far, though,for reasons that no onereally understands, thefew studies that have ex-amined stretching, toningand weight lifting havefound little to no effecton cognition. Researchersalso don't have a clearidea of how much exer-cise is too much. "Thereare very good rules forhow many hours a dayyou should work out, andhow many days a week,and what kinds of restperiods you should take-but that's all with respectto the rest of your body,"says Greenough. "As forthe brain, it's just notknown, and we need stud-ies like that."

Finally, there's the ques-tion that's been doggingCharles Hillman since hefirst picked up a hockeystick: why, if jocks on av-erage have more capablebrains than the rest of thepublic, do they have anunfair reputation for be-ing dumb? Why does aterm like "scholar-athlete:'which would have madeso much sense to the an-cient Greeks, get snick-ered at today? The reason,says Hillman, is found notin science but in common

sense: some of our schools have failedyoung athletes by cutting them too muchslack. '~lot of it comes from schools' giv-ing them an easy road:' he says. "Kids getthis wholly inaccurate label becausethey're good at sports, and then too muchemphasis is placed on their physical abili-ties at the expense of their mental abili-ties." Having a big, gorgeous, healthybrain isn't enough, of course; it also hasto be full. For that, kids have to hit thelibrary as well as the gym. "You can opti-mize your brain to learn:' says Ratey, "butthen you have to be in an environmentwhere you can do that-and you have towant it:' Sometimes, it's the "scholar," notthe "athlete," who counts. .

he "would much rather find that bio-chemical link and think about how wemight be able to reproduce the effect forthe couch potatoes."

that exercise might slowthe progression of Alzhei-mer's once it has takenhold. "By the time some-body has fairly well-developed Alzheimer's, it'sprobably too late," saysYaffe. "It's going to be dif-ficult to get them into anexercise program at thatpoint, and the damagemay already be done:'There's a grain of hope,however, to be found inanimal studies. In micethat develop a disease thatresembles Alzheimer's, atype of plaque similar towhat's found in peoplebuilds up in the brain.Carl Cotman, a neurosci-entist at the University ofCalifornia, Irvine, exam-ined those mice in 2005and found that those whospent more time runningon wheels fared betteron memory tests. Theyalso had lower levels ofplaque in their brains, hesays, possibly "because ex-ercise caused them to pro-duce less plaque and clearmore of it."

That gives rise to thequestion: if exercise is suchgood medicine, could sci-entists someday distill itsbrain-powering effects intochemical form-a sort of"workout in a pill"? The result mightend up resembling many of the drugsthat scientists are currently developingto bolster memory in Alzheimer's pa-tients. It would also surely appeal topeople who aren't willing to drag them-selves to the gym every other day."There's a resistance to maintaining anexercise program, since it involves a lotof work. People just don't feel like it,"says Ratey. "They're, like, 'I want it donefast, and I want it done now, and whyshould I have to labor over the tread-mill?' " Small, the Columbia researcher,

says many of his lab colleagues havestarted working out because of his studyresults. But, he adds, for his own part,

EFORE THAT CAN HAPPEN-that can happen-

scientists will have to answer

remain. Chief amongthem is why some forms of exercise af-fect the brain far more thanothers. Most researchers have focusedon aerobic exercise, "and they've ignoredstrength training" in the process, saysCarole Lewis, a physical therapist andcoauthor of the new book "Age-Defying

46 NEWSWEEK MARCH 26, 2007