21世纪第四单元课文

Unit4TextARunLiketheWindKristenHoelNotmanykidsknowthis,butapersoncanactuallylearnhowtorunfaster.It’strue.Eventheslowestpersonontheplaygroundcanbecomeafastrunnerbylearningandpracticingrunningtechniques.Here’show!TheBasicSkillsTherearetwobasicskillsneededforrunning:speedandendurance.Speedisthemeasureofhowfastapersoncanrun.Enduranceisthemeasureofhowfarapersoncanrun.Mostsportsrequireathletestobeskilledatbothspeedandendurance.Footballplayers,forexample,usespeedwhenmakingaplayandendurancetobeabletorunupanddownthefieldforanentiregame.Bothspeedandendurancecanbelearned.TheSecretsofSpeedTorunfast,anathletemustuseaspecialrunningtechniqueknownassprinting.Here’showitworks:First,thinkofthefootasfourseparateparts:1.heel,2.arch,3.pad,4.toes.Whensprinting,theathleteusesonlytwoparts,thepadandthetoes.Theathletestrikesthegroundwiththepadofthefoot,thenpushesoffwiththetoes.(Theheelsnevertouchtheground!)Byusingonlythesetwoparts,thestepsarequicker,andthespeedisincreased.Anotherpartofsprintingtechniqueistheuseofthearms.Itmaysoundsilly,butthearmsactuallydohelpusrunfaster.Ayoungathletecanincreasehisspeedbypracticingthesprintingtechniqueinhisbackyardorplayground.Itmaytakesometimetoperfect,butaswithanyotherathleticskill,themoreoftenonepractices,thebetteronebecomes!TheKeystoEnduranceThesecondrunningskillisendurance.Anathleteneedsgoodendurancetobeabletorunforalongtimewithoutgettingtired.Thisisaveryimportantskillinmostsports.Thekeytoendurancerunningistoconserveenergy.Thismeansusingaslittleenergyasneededtomoveoneselfforward.Aswithsprinting,thereisatechniquerunnersusetohelpthembecomebetterendurancerunners.Thistechniqueisknownasthegravitypulltechnique.Here’showitworks:First,theathleteleansforwardjustenoughsothathehastokeepsteppingforwardtokeepfromfalling.Second,heswingshisarmslong,tokeephisbalance.Finally—andhere’sthetrickypart—hestaysinthatpositionfortheentirecourseoftherun!Ittakesquiteabitofpracticetobecomeskilledatthistechnique.However,byrunningthisway,theathleteusesthepullofgravitytomoveforward,ratherthanhavingtousehisownenergytopushhimselfforward.Isn’tthatclever?ConclusionAthletesinnearlyeverysportusebothspeedandendurance.Thenicethingisthatanybodycanbecomeabetterathletebystudyingandpracticingtheserunningtechniques.Thefunnythingisthathardlyanyoneknowsthis!TextBExercise:WhatCanItDoforYou?AuthorUnknownAmericansofallagesarerunning,jumping,andliftingweightstokeepinshape.Manypeoplebelievethatexerciseisgoodforthebodyandforthemind.Theysaythatexercisehelpsthemloseweight,becomemoreattractive,orkeeptheirshapeastheygetolder.Somepeoplewhohaveverystressfullivessaythatexercisehelpsthemrelax.Thesepeoplethinkthatexercisewillhelpthemavoidthehealthproblemsthatstresscauses—suchasheartdisease.Someofthesebeliefsarefantasies:thingsthatareimpossibleoruntrue.Otherbeliefsarefacts:thingsthataretruebecausepeoplehaveproventheminstudies.Whatarethefactsaboutexercise?Canyouactuallychangetheshapeofyourbodysimplybyexercising?CananywomanlooklikeJaneFondaifsheworksout?CananymanlooklikeArnoldSchwarzeneggerifheliftsweightslongenough?Asamatteroffact,theanswerisno,notreally.Geneticsdeterminedthenumberoffatcellsyouhaveandyourmuscledefinition(howvisibleyourmusclesare)beforeyouwereborn,sothereisalimittohowmuchyourbodycanchangenowwithexercise.However,youcanloseweightbyburning(usingup)morecaloriesthanyoutakein.Exercisecombinedwithdietingcanhelp,butyouprobablywon’tlooklikeMs.Fondaunlessyoudidbeforeyoustarted.Also,youcanstrengthenandenlargeyourmuscles;thiscanimproveyouroverallappearance,butitprobablywon’tmakeyoulooklikeMr.Schwarzeneggerunlessyouwerebornwithhiskindofmuscledefinition.Whataboutreducingstressbyexercising?Infact,studieshaveshownthatdoingaerobicexercise(exercisethatincreasesyourheartrate)causesthebraintoreleaseendorphins,achemicalinyourbodythatreducespainandrelaxesthebody.Again,thereisnoguaranteethatexercisewillpreventaheartattackorastroke,especiallyifmembersofyourfamilyhavehadthesediseases.Butifyouexercise,haveagooddiet,don’tsmoke,andhavearelaxed,positiveattitude,youwillreduceyourchancesofgettingstress-relatedillnesses.TextCWalk,Don’tRunChristineGormanYouwanttogethealthy.Youknowyouneedtoexercisemore.Butifyou’renotreadytotakepartinintensephysicalactivities,don’tdespair（绝望）.There’sgrowingagreementamongexerciseresearchers（研究者）that,infact,thebestthingmostofuscandomaybetojustwalk.Yes,walk.Notrunorjog（慢跑）orsprint.Justwalkfiveorsixtimesaweek.Youmaynotfeelthebenefits（好处）allatonce,buttheevidence（证据）suggeststhatoverthelongterm（从长远来说）,aregularwalkingroutinecandoaworldofgoodtoyourhealth.Brisk（轻快的）walkingisknowntobegoodfortheheart,whichmakesalotofsense（很有道理）.Theheartisamuscle,afterall,andanythingthatmakesthebloodflowfasterthroughamusclehelpskeepitinshape.Butregularwalkingbenefitstheheartinotherwaysaswell.Itlowersbloodpressure,whichhelpsdecrease（减少）thestressonthearteries（动脉）.Walkingisalsoagreatwaytolosebodyfat,thoughmostpeoplefindtheyhavetodoitforatleastanhouradayinordertoloseweight.Thebodydoesn’treallystartburningitsfatstoresuntilafter30minutesofactivity.Exercisingtoointenselycanactuallyworkagainstyoubyinterferingwiththebody’sabilitytopullenergyfromfatcells.Youaremorelikelytomaintainanyweightlossyouachieveifyoutakeawalkregularlyeveryday.Walkingwon’tcure（治愈）everythingthattroublesyou,ofcourse,andnothinghappensovernight.“Peoplewhohaveneverexercisedregularlyshouldnotthinkthatinaweekthey’llsolve（解决）theirproblemsbywalking,”saysDr.DavidCurboftheUniversityofHawaii.Buttheycanexpectaregularwalkingpro