题目内容：
ExercisetoProtectAgingBodies--andBrains
A．Weallknowthatexerciseisgoodforyou.Stayingphysicallyactivehelpskeepyourhearthealthyandyourmusclesstrong,andincancerpatientsithasevenbeenshowntowardoffrelapse(复发).Nowaseriesofindependentlyconductedstudiesontheeffectsofexerciseonhealthyolderadults,publishedintheArchivesofInternalMedicine,confirmsthatlog-gingtimeatthegymnotonlyhelpsmaintaingoodhealthbutmayevenpreventtheattackofchronicdiseases,suchasheartdisease,osteoarthritisanddementia.
B．Inonesurprisingtrial,researchersledbyDrTeresaLiu-AmbroseattheUniversityofBritishColumbiarandomlyassigned155agingwomentothreeseparategroupsanddi-rectlycomparedthecognitiveeffectsoftwotypesofexercise:resistancetraining,doneonceortwiceweekly,inwhichparticipantsworkedoutwithfreeweightsandweightmachinesanddidsquatsandlunges,versustoningandbalanceexercises,whichpartici-pantsdidtwiceaweek.
C．Bytheendoftheyearlongstudy,thewomenwhoweight-trainedsawanimprovementintheirperformanceoncognitivetestsofmemoryandlearningaswellasinexecutivefunctionssuchasdecision-makingandconflictresolution--womenwhotrainedonceaweekimprovedtheirscoresinexecutivefunctioningby12.6%--whilethosewhodidbalanceandtoningexercisesshowednosuchimprovement.Themuscle-strengtheningexercisealsohelpedthevolunteers,ages65to75,boosttheirwalkingspeed,acommon-lyusedindicatorofoverallhealthstatusintheelderly,asfasterpacehasbeenlinkedwithlowermortality.
D．TheCanadianresearchers'findingsweresomewhatunexpected,giventhatpreviousstud-iesontheissuehavetypicallyfocusedonaerobicexercise,whichexpertsbelieveenhancescognitivefunctionbypromotingbloodflowtothebrain.Liu-Ambrosesaysherteamspec-ulatedthatanaerobicweighttrainingwouldhaveasimilareffectforotherreasons.First,aresistance-trainingregimenrequiresaconsiderableamountoflearning,especiallyforelderlypeoplewhomaynotbeaccustomedtotheequipment.Tolearnhowtousedumb-bells,alegpressoralatissimuspull-downmachinecorrectly,forexample,thevolunteerswererequiredtofocusonthetaskathand,masternewtechniquesandretainnewinforma-tionaboutproperandsafeuseofequipment.Previousstudieshaveshownthatsuchlearn-ingcanhelpolderadultsmaintainmentalacuity.
E.Thewomenalsohadtoremembertheirweightsettingsandadjustmentstotheseatsandkeeptrackofthenumberofrepetitionstheycompleted,saysLiu-Ambrose."Thereisalotmorelearninginvolvedthatmaynotoccurifyoutakeupawalkingprogram,"shesays,notingthatittookthevolunteersagoodtwomonthstogetcomfortablewiththeequipmentandthetrainingregimen.Inaddition,Liu-Ambrosesays,otherstudieshavefoundthatpeoplewhoweight-trainshowanincreaseinbloodlevelsofagrowthfactorthatisimportantformaintainingskeletalmass.Thisfactor,ittumsout,alsopromotesnervegrowth,whichcouldbeanotherwaythatresistancetrainingboostsmentalfunc-tion.
F.Inasecondbrain-functionstudy,publishedinthesamejournal,scientistsinGermanyfoundthatincreasedphysicalactivitywasassociatedwithalowerincidenceofdemen-tia.Inthisstudy,researchersrecruited3,485elderlyresidentsinBavariaandaskedthemabouttheirphysicalactivity.Noneoftheparticipantshaddementiaatthestartoftheanalysis,butaftertwoyearsoffollow-up,researchersfoundthatthose,whoexercisedatleastthreetimesaweekwerehalfaslikelytohavedevelopeddementia,comparedwiththepeoplewhoreportednophysicalactivity.Basedonhisresults,saysleadauthorDrThorleifEtgen,aprofessorofpsychiatryandpsychotherapyatMunchenUniversity,"itdoesn'tmakeabigdifferenceifyouhavemoderateorhighphysicalactivity.Theim-portantmessageisthatyoudoanyactivity.Andevenifyoustartlateinlife,at60or70,thereisabenefit,forit'snevertoolatetostartexercising."
G.Thekeywordsare"moderateorhigh",accordingtoanotherstudythatwaspublishedintheArchivesofInternalMedicine.DrQiSun,aresearcheratHarvardSchoolofPublicHealth,analyzed13,000womenparticipatingintheNurses'HealthStudyandfoundthatwhenitcametoexercise,morewasbetter.Comparedwithwomenwhojoggedfor20minutesaweek,thosewhojoggedthreehoursaweekorwalkedbrisklyforfivehoursaweekwere76%morelikelytoagesuccessfully,freeofchronicillnessessuchascancerandheartdisease,aswellasmentalandphysicalimpairment.Sun'sgroupfoundthatthisbenefitoccurredacrossallweightdivisions,meaningthatevenamongthosewhowereoverweightorobese,womenwhoexercisedimprovedtheiroddsofagingwithoutchronicdisease.Theeffectsmayapplyacrossdifferentagegroupsaswell;thewomenwereatleast60yearsoldbythetimetheyenrolledinthestudy,andwhileSunwasnotabletodeterminehowlongtheyhadbeenexercisingpriortothat,theresultssuggestthatthehealthbenefitsarenotlimitedtotheyoung.
H.Thatwasthesamemessageofthefinalexercisepaperinthejoumal,byresearchersatUniversityofErlangen-NuremberginGermany.Inthistrial,agroupof246elderlywomenwererandomlyassignedtoan18-monthexerciseregimenorwellnessprogram.Thewomenparticipatinginthefour-times-weeNyexercisesessions,whichinvolvedaerobicsandbal-anceandmuscletraining,improvedtheirbonemineraldensitybynearly2%.Thewomeninthewellnessgroup,whichfocusedonwalking,musclerelaxationandbreathingskills,hada0.33%increaseinbonemineraldensityoverthesametimeperiod.
I.Despitethepositiveevidence,however,notallresearchersarereadytosuggestthatexerciseisasure-fireprescriptionagainstmentaldeclineorchronicdiseaseinhealthypeople.Tomakethatclaim,alarge,longer-term,controlledtrialwouldbeneeded,inwhichparticipantsarerandomlyassignedtoexerciseornot,andarethenfollowedforthedevelopmentofchronicconditionssuchascancer,heartdiseaseordementia.Still,saysDrMarcoPahor,directoroftheInstituteonAgingattheUniversityofFloridaandauthorofacommentaryonthestudiesappearinginthejournal,"ifyoupoolalltheevi-dencetogether,thebenefitsofexerciseseempromising."
Expertsbelievethattheaerobicexercisesraisepeople'scognitivefunctionbystimulat-ingbloodblowtobrain.
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