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Coaching the Sprints, Hurdles, and Relays 71

4.TeachathletesthattypeIIb(fast-twitch)fibersareonlyrecruitedduring greatforcedemand.Forcedemandcanbeincreasedbysprintingshort distancesatfullspeedandbyrunningwithaslightresistance.

Biomechanical Principles of Sprinting

Biomechanicsisthestudyofhowthebodyrespondstothelawsandprinciplesofmechanicsandphysics.Conceptssuchaslevers,gravity,Newton's laws,andsoforthareusedtolearnhowthebodycanbemoreeffective.Here, weconsiderthesethreepoints:actionandreaction,conservationofangular momentum,andtheroleofpostureincreatingastretchreflex.

Action and Reaction

YoumayrecallNewton'sthirdlaw:Foreveryaction,thereisanequaland oppositereaction.Insprinting,thisfundamentalconceptcanbeusedtomake surethatarunnerisfocusingontherighttechnicalpoints.Whatactionscan sprintersperformthatwillcausetheintendedreactionofmovingdownthe track?Themainideaistostrikethetrackwiththefootinawaythatwill propelthebodytowardthefinishlineasquicklyaspossible.Thismeanstwo majorthings.First,theathletemuststrikethetrackwiththefootinawaythat generatesmovementhorizontallytowardthefinishline.Bouncingupand downisinefficientandslow.Thesecondpointisgroundcontacttime.The quickerandmoreforcefullythesprinterstrikesthetrack,thefasterthereturn willbe.Long,slowgroundcontactscauseslowrunning.Sprintingrequires quickandpowerfulfootcontacts.

Conservation of Angular Momentum

Ashortlimbmovesfasterthanalonglimb,butalonglimbcangeneratemore force.Thistrade-off,knownasconservationofangularmomentum,comes intoplayinsprintingintwomajorways--heelrecoveryanddevelopmental considerations. Asprinterneedstomakethelegasshortaspossibleasitswingsforward (thispartoftherunningstrokeisknownasheelrecovery).Liftingtheheelto thetopofthehamstringimmediatelyfollowingtheactivebackwardcontact strokeshortenstheleverofthefreelegandcreatesfasterreturn.Also,when thelowerlegistuckedclosetothethighduringtherecoveryphase,strainon thehamstringisreduced.Alowheelrecoverycreatesalongandslowlever thatthehamstringhastocontroltokeepthekneefromoverextending.In otherwords,becausetheleverislong,itcanproducemoreforce,andthe hamstringhastoworkhardtodeceleratethelowerleg.Properheelrecovery ismoreefficientandreducesthechanceofinjury. Regardingdevelopment,youmustunderstandthatchildrenmightnothave themuscularstrengthtoholdtheirarmsinadisciplinedform.Thelimbs, especiallythearms,formlongleversthatmaybecreatinggreaterforcethan theathletecancontrol.Someathletesregulatethisbyfoldingtheirarmstightly

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Coaching Youth Track & Field

attheelbowstocreateveryshortarmlevers.Thissolutionmaystopthecoach fromnaggingaboutwavingarms,butitisnotpropertechnique.Learning tocontrolthearmsisimportant,butitmustbeaddressedthroughgeneral strengthdevelopment,aswellaspatientteachingofpropertechnique.

Posture and Stretch Reflex

Connective tissue has elastic qualities, and recruiting this elastic potential makessprintingmoreefficient.Elasticityisincreasedbyholdingproperposture.Tomaintainproperposture,athletesmustlearnthatthehipsneedto beheldinaslightly"tucked"positionduringallphasesofthesprintraces. Tuckedhippostureisefficientbecauseitsetsupastretchreflexoftheconnectivetissueonthefrontofthehipsandlegs.Thistissueactslikerubberbands andpullsthelegbackinfrontofthebody.Thinkofthiselasticresponseas "freeenergy"thatdramaticallyimprovesrunningeconomy.Failuretohold thehipsintheproperpositionshortensthelengthofthestretchinthefront ofthebodyandreducestheelasticresponse.Furthermore,whenpoorhip postureshortensthestretchinthefrontofthebody,itlengthensthestretchin thebackofthebody.Thiscausesthehamstringtodomoreworkandexposes ittorangesofmotionthatcanberisky,especiallyinstatesoffatigue. Theshouldergirdlealsousesastretchreflexinsprinting.Theactivephase ofthearmactioniswhenthearmmovesaggressivelybackward.Asthearm movesback,theelbowopensslightlytoelongatetheleverandcreateabitmore force.Thearmshouldgototheendoftherangeofmotion(elbowaboutas highastheshoulder)andcreateastretchoftheshoulder'sconnectivetissue. Thearmclosesabitattheelbowasthearmreturnsinanelasticreflex.

The Three Phases of Sprinting

Thesprints--whetherit'stheactualsprints,thehurdles,ortherelays--are brokendownintothreephases:acceleration,full-speedrunning,andrunning fastinastateoffatigue. Asacoach,youwillwanttoteachthesephasesintheordertheyoccur.In otherwords,athletesmustfirstlearnhowtogetuptofullspeed.Thenthey canpracticerunninghigh-qualityeffortsatfullspeed,includingusingproper techniqueatmaximumvelocity.Finally,theycanworkonmaintainingfast runningwhilefatigued.Toooften,coachesputtogethertrainingprogramsin theoppositeorder.Startingtheseasonwithspeedenduranceworkwhenasolid baseofspeedhasnotbeenestablishedisaquickroutetoplateaus,frustration, andinjury.Ifanathleteisnotgoingfastduringasetofrepeats,especiallynear thefinishline,theathleteisnotreallytrainingforthesprints.

Acceleration

Theobjectistotransitionfromastillpositiontofull-speedrunningasquickly andefficientlyaspossible.Theathleteshoulduseaforwardlean(seefigure 7.1a)whenacceleratingfromastillposition.However,thismustnotbeover-

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