Research Article. Relative analysis of Taekwondo back kick skills biomechanics based on 3D photograph parsing. Mingming Guo

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1 Available olie Joural of Chemical ad Pharmaceutical Research, 203, 5(2):64-69 Research Article ISSN : CODEN(USA) : JCPRC5 Relative aalysis of Taekwodo back kick skills biomechaics based o 3D photograph parsig Migmig Guo Istitute of Wushu, Sheyag Sports Uiversity, Sheyag, Liaoig, Chia ABSTRACT As photographig ad video parsig techiques improved, it provides a boost for taekwodo techical researchig. This paper make aalysis of every stage features of back kick skills by usig video parsig data, the based o aalysis huma gravity shiftig features ad relative features betwee hip agle ad kick velocity i motio process, through aalysis of each lik of lower limbs velocity status i five time phrases, get every liks of lower limbs velocity feature i 4 stages. With the aalysis data of taekwodo back kick motios time cosumig i 4 stages, get the order of time cosumig proportio from biggest to smallest like : the 4th stage> the st stage>the 2d stage>the 3rd stage; it provides theoretical basis to sports aalyzig ad data refereces to taekwodo traiig. Key words: Back Kick Techiques, 3D Photograph Aalysis, Correlatio Idex, Gravity Displacemet INTRODUCTION Taekwodo is a kid of kickboxig sport, itegrated competitio of athlete s itelligece, eergy, techiques, skills ad willpower as well as others are required to wi the game, but the movemet core still is the utilizatio of sports techique, therefore lots of resources are ivested to the research of techique motios, while by far the best the studyig method is to get every motio of oppoets i close rage through visual chaels, ad the decode sports mechaics parameters accordig to video aalysis system. Out of may skilled motios i taekwodo, back kick plays a role i sports score, ad this paper is accordigly study the 3D photograph aalysis data of taekwodo back kick motio to gai its sports feature. May scholars have made efforts i successio to the study of taekwodo ad 3D image resolutio techiques, provide theoretical basis ad experimetal platform to their orgaic itegratio, ad image resolutio techiques cotiuously ifiltratio to sports aalysis, some domestic scholars cotribute their ow thought ad research results. Amog them, Zhag Yog [] Apply 3D image resolutio techiques i trackig techical moitorig ad aalyzig of me ad wome athletes o 20km trai walk at our 29th Olympic games. Che Yu[2] Started from diagosis, researchig taekwodo crescet kick techiques, fid out athletes motios advatage ad disadvatage through compariso of two athletes joit velocity, joit movemet trajectory ad required time i completig motios; Zhag B. [3] use 3D photography ad electromechaically sychroous method, make biomechaics aalysis of taekwodo players o-site back kick motios, get back kick motios data as time, displacemet, velocity, gravity chages as well as the residual motios mai muscle s origial electromyography,itegrated electromyography ad every muscle s active order so o other data through 3D photographig, from which the essetial traits of back kick techical motio be more deeply, comprehesively revealed,provide theoretical basis refereces to taekwodo back kick techical traiig[4]. This paper, o the basis of previous study, use 3D photography techiques ad image resolutio system, collect sports parameter ad biomechaical parameters of taekwodo back kick techical motio, explore back kick techical motios features through data, provide theoretical basis to sports aalysis ad scietific guidace. 64

2 EXPERIMENTAL SECTION Measuremet techiques ad study method Utilize high-speed photography method to collect ad aalysis techical motios i sports, ad the method has bee valued uiversally by sports researchers. This paper study o taekwodo back kick motio s biomechaical features, provide reliable data for researchig. Measuremet techiques: Whe huma body proceeds with quick motio, image recordig system should be applied if all motios space features at every momet eed to be captured. I sports researchig, high speed photography test also do image aalysis to huma movemets, the aalysis is composed of 2D ad 3D aalysis, from which 2D aalysis is plae filmig, take photos of sports images ad defie the 2D coordiates of researchig objects huma body joits by usig a high speed camera, calculate relative data s origial idex as the required displacemet, velocity, accelerated velocity, agle, agular displacemet, agular velocity ad agular accelerated velocity so o through aalyzig ad smoothig, so as to evaluate sports techiques; While 3D photography ad aalysis is to take photos of huma movemets with 2 sychroous high speed camera from differet agles, get relative equipmet poits 3D space coordiates through liear trasformatio betwee 2 cameras 2D films, the calculate required displacemet,velocity, accelerated velocity, agular displacemet, agular velocity ad agular accelerated velocity so o relative idex, provide data basis to sports techical feature aalysis. This paper utilize 3D photography ad aalysis method, use two high camera at frequecy of 20HZ to do sychroously shot, take AI JIE 3D radiatio space frame as stadard frame, adopt America ARIEL sports biomechaics resolutio system APAS to aalyze videos, do aalytical processig by usig huma body iertial parameter model ad select 9 joits to whole back kick motios aalyzig based o model s stadards ad researches, smooth the aalytic data with filter method. Take two high speed cameras to shot fixed equipmet 3D video of athletes back kick techiques, oe camera located o the frot left side 2m ext to tester, its height is.m, the other located o the back right 2m ext to tester with the same.m height, the pricipal optic axis itersectio agle betwee such two camera is 20º,athletes eye frot foot target, left foot o the frot,right foot o the back, make back kick motio with passwords, foot would fially kick o the ceter of target, as Fig. the test spot overlook schematic diagram show, A-F i Fig. are respectively represets cameras. Fig.: Overlook figures o imagig testig spot Research Objects ad Methods: Research Objects: Select taekwodo domestic master sportsme ad first grade sportsme total players. I order to easily explaatios, express them with P-P, the players status show as below Table. Table: research objects status list Athletes Age Height Weight traiig years Grade P P P Master sportsme P P P P First grade sportsme P

3 Research method: Make features aalysis to camera s measurig data with mathematical statistics, take athletes every data s average value plus ad mius stadard deviatio to idicate every data features. The computatioal formula of average value plus ad mius stadard deviatio x ± SD as formula () show. x = SD = ( x + x + + x ) 2 L ( x x) i 2 () Taekwodo back kick techical aalysis Back kick motios stage divisio ad features: Motios of Taekwodo back kick ca be divided ito 4 stages as prelimiary posture, tur ad fold aticipatio of body ad kickig legs, hip extesio ad kee extesio kickig, fast reductio after kickig.so as to well aalysis every items data of taekwodo back kick techical motio, movemet process ca be divided ito 5 time phases ad 4 stages agai with above 4 stages basis, first phase is the momet that support foot start turig ad body turig back, secod phase is the momet that kickig foot off the groud ad kees start up, the first stage s turig start betwee first ad secod phases; third phase is the momet that kickig at miimum leg itersectio agle, the secod stage s turig ad kees up betwee secod ad third phase, fourth phase is the momet that leg kickig to the target, the third stage hip extesio ad kees extesio kickig betwee the third ad fourth phases, fifth phase is the momet that kickig legs ladig ad restorig, restorig after kickig stage betwee the fourth ad fifth phase. The eight research objects time cosumig status i 4 states as Table 2 show. Table 2: Table of Taekwodo back kick motios time cosumig status i 4 stages Athletes First stage time Secod stage time Third stage time Fourth stage time cosumig cosumig cosumig cosumig Total P s s s s.367 s P s 0.20 s 0.27 s s.325 s P s s 0.67 s s.259 s P s 0.3 s 0.27 s s.225 s P s s s s.20 s P s 0.20 s 0.34 s 0.54 s.23 s P s s 0.4 s 0.70 s.450 s P s 0.3 s 0.92 s s.40 s Taekwodo back kick is a typical turig ad kickig motio, its 4 stages closely coected, requirig better cosistecy of techical motio, i turig process, head should lead body fast tur ad shift body ceter, fold aticipatio betwee body ad kickig legs directly affects back kick s quality; i aticipatio process, hip extesio ad kees up kickig provides larger turig velocity, while i quick kick ad fast restorig process, the balace of body ceter of gravity should be adjusted well. Data i Table 2 idicates that o big differece amog athletes back kick motios total cosumig time, the average value i the rage of.36 ± s, the third hip extesio ad kees up stage out of the 4 stages cosume the shortest time, the average value i the rage of 0.9 ± s, ad the other stages time cosumig order from smallest to biggest are Secod stage <First stage< Fourth stage, their average values are respectively i the rage of ± 0.07 s,0.323 ± s ad ± s. It ca be cocluded from above that time features is more obviously i 4 stages, ad the 4 stages average time cosumig ituitive status as Fig.2 show. Fig.2: Proportios of every stages average time cosumig o totals 66

4 I Fig.2, -4 are respectively represeted as the first stage, secod stage, third stage ad fourth stage s average cosumig time ad average total cosumig time ratios. Data i Table 2 idicates that the shortest time cosumig i stage is 0.233s from P5,while both P6 ad P used the logest time of 0.400s, sice athletes muscle i differet coditio after activated i stage,some laggig would be happeed i trasitioal gravity shiftig process, velocity i this stage therefore has more room for improvemet; I secod stage athlete P4 cosumed the shortest time of 0.3s,while P7 used the logest time of 0.233, body turig i this stage is leaded by head,fast turig ot oly shorte eyes away from oppoets, but also reflexive accelerate body s turig velocity, iertia thus icreased ad recover first stage s body gravity ceter siftig s laggig to some extet; I the third stage, athlete P6 cosumed the shortest time of 0.34s, while P4 used the logest time of 0.27s,the kick leg should be folded ad closely clig to support leg ad make kickig i lie i this stage, meawhile larger turig velocity geerated i the turig ad hip rotatig lead to fast kickig ;I fourth stage athlete P4 cosumed the shortest time of 0.433s wile P7 used logest time of 0.70s, athletes tured two legs supportig of prelimiary posture ito sigular leg supportig i this stage, its bearig areas has bee arrowed dow, gravity at the momet has bee shifted from two legs to sigular led ad the chage ito the frot area of sigular kicked leg s bearig area, these chages will decrease huma body s stability to some extet. I coclusio, back kick techiques has some characteristics as log fulfilled time requirig, difficult, but the techical motio quite powerful, timig should be mastered i its applicatio. Huma body gravity ceter variatio features i back kick process: I taekwodo back kick techical motio processig, huma body chages prelimiary posture of legs support ito sigular leg support, huma body s gravity lie shift from legs middle area to sigular leg, the ito the frot of kicked leg supportig area. Istability of gravity i back kick processig show as displacemet shiftig distace,gravity ceters displacemet variatios ca be got from 3D photography ad video aalysis, as it show i Table 3 huma gravity locatio variatio status. Table 3: Table of Huma gravity coordiates displacemet variatios i Taekwodo back kick processig Athletes X axis displacemet variatios Y axis displacemet variatios Z axis displacemet variatios P P P P P P P P Three directios displacemet variatio s chagig tedecy ca be got from Table 3 s data, as Fig.3 show. Fig.3. Displacemet variatios i 3 coordiate directios I Table 3, X axis ad Y axis gravity displacemet variatios represets gravity ceter s horizotal versus vertical displacemet rage, athlete Pgets the largest displacemet variatios of 0.74m i X axis while P7 gets the smallest oes of 0.39m.Though idividual differeces existig amog athletes gravity ceter i movemet directio, displacemet i movemet directio is surely the overall tred of taekwodo athletes back kickig process, legs support-->turig sigular support-->forward after kickig, Athlete P gets the largest displacemet variatios of 0.4m i Y axis while P5 gets the smallest oes of 0.02m.It ca be see that idividual differeces existig o athlete s horizotal displacemet i Y axis. Sice average value fluctuates iside the rage of ± 0. 04, better stability here ca be cocluded i back kickig, direct leg movig ad eckig, abdome stretchig, hip abductio are 67

5 helpful to effective kickig i back kick techiques. Athlete P6 gets the largest displacemet variatios of 0.059m i Z axis while both P3 ad P gets the smallest oes of 0.002m.It ca be see that larger fluctuatio i average value of athletes gravity ceter risig. However, body ca be straighte to tured,kees up, hip cotractig,fially ito shoulder withholdig, hip extesio, kees extesio i taekwodo back kick techical motios, less up ad dow chagig o athletes gravity ceters is required to keep body stability i this process. I coclusio, the whole back kick techiques movemets should keep dyamic stability of gravity ceter so that more helpful to esure kick stregth ad velocity. Relative performace aalysis of hip rotatio ad back kick foot velocity: The most basic symbol to show taekwodo back kick techical motios efficiecy is the valid scores, legs fast; correctly, powerfully kickig to oppoet score positio is required to get such valid scores. The larger velocity kickig leg geerated i kickig, the better efficiecy i back kicks. I back kick turig process, hip joit produces a larger turig agular velocity, the faster agular velocity got, ad the larger kickig velocity would be got from kick leg. I order to make a more accurate research o hip rotatio ad kick leg velocity, this paper collect athletes kick leg s velocity value ad hip rotatio agular velocity value i the kickig momet to study the relatioship betwee traslatioal velocity ad agular velocity, as Table 4 show. Table 4: Data list of hip rotatio agular velocity ad kickig leg velocity Athletes kickig leg velocity hip agular velocity P.470 m/s deg/s P2.36 m/s deg/s P3.399 m/s deg/s P m/s deg/s P m/s deg/s P m/s deg/s P m/s deg/s P.609 m/s deg/s Give hip agular velocity the idepedet variableω, while foot velocity as depedet variable v, scatters image represetatio betwee the two as Fig.4 show. Fig.4: Relatio Image betwee Hip agular velocityω ad kickig leg velocity v The computatioal formula of correlatio idex r of ω v data as formula (2) show. r = ( vi v )( ωi ω ) 2 ( vi v ) ( ωi ω ) 2 (2) Relative idex r is calculated out that is equal to 0.933, it idicates ω v obviously correlated, that is to say whe agular velocity hip icreased; kickig legs velocity would be icreased accordigly. Back Kick motio s lower limbs joit speed features: I taekwodo back kick movemets, lower limbs every segmets speed costatly spread from ear side to far side, though eergy loss would be geerated i the spreadig process, accordig to agular mometum coservatio law, it ca be ackowledged that i case ear side segmets ows high quality, far side oes ows lower quality, the fial velocity of far side ormally would be icreased. I 6

6 foot s back kick process, ear side segmets is thigh, ext oe is shak, while far side segmet is foot. Followed by segmets poit icreasig, its quality become more ad more lower, therefore foot velocity begis to spread sice large segmets, so that the hip ad kee speed chages i back kick techical motios have great effect o foot fial speed. So as to explore segmets speed i each phase, 3D photography ad aalysis method are applyig i collectig 5 phases hip, kee ad foot istataeous speed o this paper, as show i Table 5. Table 5: Table of lower limbs velocity i every phase Lower limbs segmets First phase Secod phase Third phase Fourth phase Fifth phase Hip Kee foot 0. ± ± ± ± ± ± ± ± ± Distributio features of every lower limbs segmet i five phases as Fig.5 show. 0.6 ± ± ± ± ± ± 0.0 Fig.5: every segmets velocity features i 5 phases It ca be cocluded from Fig.5 that hip speed arrived largest i secod phase, ad the secod stage keeps approximate maximum speed while the fourth phase get the lowest speed. I the 5 phase speeds, except for first phase startig turig speed faster tha other segmets, hip speed i other phases all lower tha other segmets; kee ad foot speed all reach the fastest i the third phase, while be slowest i first phase, both of them icreased i first ad secod phases, started to decrease sice the third phase, kee from the two has slightest speed chages i the fourth phase, while foot speed decreased i the fourth phase; the three segmets have roughly the same speed i the secod ad fifth phase. CONCLUSION O the basis of research o taekwodo back kick techical motios measuremet techiques, utilize 3D camera pricipal, provide scietific layout plaig to test sites; This paper select taekwodo athletes as research objects, four of them are coutry s master sportsme while other 4 are first grade sportsme, ad idicate the athlete s body parameters, preset data hadlig method, provide computatioal formula of usig average value plus ad mius stadard deviatio. Make data aalysis of taekwodo back kick motios time cosumig i 4 stages, get the order of time cosumig proportio from biggest to smallest like: the 4th stage> the st stage>the 2d stage>the 3rd stage; Huma gravity ceters variable status i taekwodo back kick techical motio process were studied, importace of gravity ceters stability ad its displacemet variables root cause were aalyzed. Hip rotatio agular speed ad foot speed relatios were studied, obvious correlatio ship betwee the two were foud through data, that is whe hip rotatio speed icreased, foot speed would also be icreased accordigly; Hip, kee ad foot these three segmets speed status i every phases were aalyzed, every segmets speed variable tedecy ad its feature i 4 stage were cocluded. This paper is biomechaics aalyses of taekwodo back kick techical motio, scietific measuremet site as well as excellet level ad quality research objects were desiged, implemetatio process of mathematical statistics method also was provided so as to get reliable mechaical parameters. 69

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