1 아웃도어워킹화개발을위한근피로도및지면반력의생체역학적분석 2 3 4 The Biomechanical Analysis on Muscle Fatigue and GRF for Outdoor Walking Shoes Development 5 6 7 Young-Min Jang 1 Joong-Sook Lee 2 Jong-Ok Yang 2 Bom-Jin Lee 2 8 9 10 1 Business Support Team, Ulsan Economic Promotion Agency, Ulsan, Korea 11 12 2 Division of Kinesiology, College of Health and Welfare, University of Silla, Busan, Korea 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 Corresponding author Joong Sook Lee, Ph.D. Professor Department of Kinesiology / 140, Baekyang-daero 700beon-gil, Sasang-gu, Busan Silla University Phone: 051-999-5064, Fax: 051-999-5164, Email: jslee@silla.ac.kr 1
30 31 32 33 Abstract Objective : The purpose of this study is to analyze different kinds of outdoor walking shoes muscle fatigue and ground reaction force at walking comparatively and provide foundational data that can help develop outdoor walking shoes and select outdoor walking shoes that fit the users. 34 35 36 37 38 39 Method : The study objects were 30 healthy males. The experiment is conducted on outdoor walking shoes of which mid sole s inner and outer harness is different and out soles shape is different. For data collection, the EMG is used to measure the muscle fatigue of anterior tibial muscle and gastrocnemii contributing to the dorsiflexion and plantarflexion of the ankle joint and also of biceps muscle of thigh and lateral great muscle contributing to the flexion and extension of the knee joint. GRF measurer was used to measure the axes of X, Y, Z. 40 41 42 43 44 45 Results : In type A outdoor walking shoes, regarding the mid sole s hardness, the inner part is soft while the outer part is hard. The vertical ground reaction force is the lowest, which means that you will get the least impact while walking, and your knees and ankles will experience little load. In type C outdoor walking shoes, they are intended to give good feel of wearing. Tibialis anterior, Biceps femoris and gastrocnemii indicate low fatigue, which means that during a long-distance walk, it will minimize the fatigue in your lower limbs muscles. 46 47 48 49 50 Conclusion : To sum up the above results, the different types of outdoor walking shoes indicate their unique characteristics in the biomechanical comparison and analysis. However, it is not statistically significant difference, so it is needed to conduct systematic and constant follow-up research afterwards to cope with the outdoor walking shoes market that is getting bigger. Lastly, this study is expected to present foundational materials and directions for developing outdoor walking shoes. 51 52 53 54 55 56 57 58 59 Keywords : Outdoor walking shoes, Muscle fatigue, GRF, Mid sole hardness, EMG, Long-distance walk Introduction 최근에들어서여가선용의목적으로일반적인걷기나산책에서벗어나다양한코스에서아웃도어워킹 (Outdoor walking) 을즐기는인구가증가하고있으며, 이에따라워킹의개념을레저의관점으로바라보는시각도증가하고있다. 신발과워킹은서로떨어질수없는관계이며신발은보행동안지면착지시에발생하는충격을흡수하고발목을포함한인체의여러관절을보호함으로써부상예방의역할 (Choi & Kwon, 2003) 과이동의목적으로사용되어왔다. 그러나다양한환경과코스에서 2
60 61 62 아웃도어워킹을즐기는인구가증가함에따라신발고유의목적과특성을더욱부각시켜신발을 과학화하려는노력이기능성, 경제성, 미관성의측면에서더욱개선되어지고있다 (Ryew & Hyun, 2013). 63 64 65 66 최근들어새로운기능이첨가된신발의개발이활기를띠는경향을보이고있는데오랜세월을두고점진적으로발달된신발이갖는기능은사용목적이많아짐에따라다양화되었으며, 자세의균형과안정성은보행에있어중요한요소이며, 신발밑창의구조가보행특성에영향을미친다 (Landry et al, 2010; Miriam, 2015). 67 68 69 70 71 72 73 이러한이유로신발의기능과종류에대한선행연구들을살펴보면기능성구두와맨발보행시하지관절각도및부하율비교분석 (Lee & Nam, 2015), 신발의종류에따른발바닥부위별압력분포의차이 (Yi, 2010), 기능성신발과일반운동화의운동역학적비교분석 (Song, Lee, & Sung, 2008), 신발종류와이동속도에따른보행의운동역학적분석 (Lee & Sung, 2008), 등산화의종류와보행동작에따른지면반력및족저압력분석 (Park & Lee, 2007) 등이있고, 신발밑창형태가무릎및발목근육의근활성화에미치는영향 (Yoon, Lee, & Choi, 2014), 보행시신발밑창형태가하지근활성도에미치는영향 (Kim & Choi, 2012) 등이있다. 74 75 76 77 78 79 80 81 82 83 신발에만국한된연구뿐만아니라, 신발의밑창, 즉인솔에대한연구도많이이루어지고있다. 선행연구로는트레드밀보행시인솔형태변화에따른족저압력분석 (Woo et al., 2015), 보행시키높이인솔이젊은남성의하지관절에미치는영향 (Shin et al., 2012), 탄소나노튜브인솔착용에따른드롭착지동작의생체역학적분석 (Chae, Jung, & Lee, 2012), 보행시보급형키높이인솔의높이와재질이평균족저압에미치는영향 (Lee, Kim, Jung, Han, & Park, 2011), 보행시변형및복원이가능한인솔에대한족저압력비교분석 (Park, Lee, Kim, Yoo & Kim, 2011) 등이있으며, 신발이나인솔자체만의기능에관한것보다보행이나주행시신발이인체동작이나안정성에미치는영향을연구한것이주종을이루고있다. 이와같이신발에관련된연구는지면반력과족저압력에관한연구가최근많이수행되고있으며, 이러한연구결과들을기초자료로활용하여신발개발에다양하게활용하고있다. 3
84 85 86 87 88 89 90 91 아웃도어워킹을위한신발은일반적으로부상에대한예방및보호를중요하게생각하고발과신체의안정성향상을위한기능을갖추어야된다 (Stewart et al., 2007). 현재아웃도어워킹화에대한연구가활발히진행중인데, 아웃도어워킹화라커솔형태에따른즉각적인보행전략차이에서라커솔의생체역학적효과는통증이나기형, 경직이있는발이나발목의운동을회복시켜주어보행을향상시키고, 발바닥특정부위에주어지는압력을경감시켜주며균형능력향상에도움을준다고하였다 (Yi, 2008). 또한, 기능성워킹화가족형, 균형, 유연성그리고신체구성에미치는영향에서워킹화를착용한후걷기운동을통해발목의유연성뿐만아니라몸통및팔의유연성도증가했다고보고하였다 (Yi, 2007). 92 93 94 이외에도중량물을부가한워킹화신발바닥의적정경도분석 (Kwak & Jeon, 2011), 발끝이 최대높이까지올라간워킹화가신체구성, 체력, 건강관련변인에미치는영향 (Yi, 2005) 등워킹화의 다양한연구가이루어지고있다. 95 96 97 98 또한, 최근에이루어지는아웃도어워킹화연구를살펴보면, 지면반력측정기를이용한충격력분석및이를토대로한신발중저 (mid-sole) 의경도및외부구조개선분야, 영상분석법을이용하여후족제어 (rear-foot control) 기능을연구하고신발의안정성을증진시키는데활용하는분야, 압력분포측정기를이용하여신발밑바닥의압력분포를측정하는분야로나눌수있다 (Shin, 2007). 99 100 101 102 103 104 105 106 이와같이아웃도어워킹화개발에대한노력이활발하게이루어지고있는것은매우바람직한것이며, 아울러신발이갖는과학적기능에대한체계적인연구결과는국민건강을위해뒷받침되어야할내용으로체육과학적연구가절실히요구된다. 특히, 다양한아웃도어워킹화가개발됨에따라아웃도어워킹화의운동학적 (kinematic), 운동역학적 (kinetic) 인연구의필요성이대두되고있으며, 특히운동학적, 운동역학적기능분석및평가는신발이갖는기본적기능에관한것으로연구의필요성이높다고할수있다. 그러므로본연구의목적은아웃도어워킹화종류에따른운동역학적변인을비교분석함으로써아웃도어워킹화개발을위한최적의조건을구명하고, 이러한연구결과를활용하여아웃도어워킹화개발의기초자료를제공하고자한다. 107 4
108 109 110 111 112 113 114 115 116 Method 1. Participants 연구대상자는하지의질환경험이없었고, 정상적인보행형태를가진신체건강한 20 대남자 30 명을연구대상으로선정하였다. 실험전연구의목적과절차를설명하고, 피험자가자발적으로실험참가동의서에서명한후실험을실시하였으며, 모든실험에앞서연구대상자들에게충분히워밍업 (warming up) 을하게하였다. 대상자들의신체적특성은 <Table 1> 과같다. 117 Table 1. Subjects information (N=30) Items (M±SD) Age(yrs) 22.10±1.45 Weight(kg) 69.90±5.80 Height(cm) 177.10±2.85 Foot length(mm) 270±0.00 118 119 120 121 122 123 124 125 126 2. Measurements 5
127 128 1) 신발 129 130 4 개의아웃도어워킹화유형별생체역학적분석을실시하였으며, 실험에사용된신발은 <figure 1> 과같다. 131 132 133 Figure 1. Type A, B, C, D outdoor walking shoes 134 2) 측정도구 135 (1) 근피로도측정 136 137 본연구에서하지근육의피로도증가량을보기위해미국 Noraxon 사의 TeleMyo DTS Telemetry 와 Noraxon XP 상용소프트웨어를사용하였으며, 장비는 <Figure 2> 와같다. 6
138 139 Figure 2. NORAXON s wireless electromyograph 140 141 142 Figure 3. The surface electromyography electrode and muscle measurement placement 7
143 144 145 146 147 148 149 150. 하지근육의근피로도를분석하기위해트레드밀에서 4.2 km/h 의속도로 60 분간보행시하지근피로도를블루투스방식의무선근전도측정시스템을사용하여측정하였다. 또한, 보행시가장큰힘을발휘하는근육인대퇴이두근, 장시간보행시파워및근지구력을유지시켜주는비복근, 하지의굴곡및신전에관여하는외측광근, 발을바닥에서들어올리고내리는역할을하는전경골근, 즉, 하지에서가장활발한근육활동을하는 4 부위근육을측정하였다. 근피로도검사는보행전과 60 분간보행을실시한후 MPF(Mean Power Frequency) 값에대한 EMG 변화량을측정한후분석하였다. 보행전각피험자와근육별로 MPF 값간의차이는 Normalized 된값을사용하였으며, Normalized MPF 값은다음식과같이도출하였다 (figure 3).. 151 Normalized MPF = 보행 60 분후측정한 MPF 평균값 / 초기측정한 MPF 평균값 152 153 154 위공식을바탕으로근피로도에관한선행연구결과 (Kong et al., 2009; Park et al., 2010) 에따르면 Normalized MPF 값을도출한근피로도산출결과 MPF 값이 1 보다작을수록근피로정도가높아지고 1 보다높은값을가지거나비교군보다높은값을가지면피로도가낮은것으로보고했다. 155 156 (2) 지면반력측정 157 본연구에서지면반력을측정하기위해 Bertec 사의 4060-10-2000 지면반력측정장비를사용하였으 158 며, 장비의규격은 <Table 2> 와같다. 지면반력을측정하기위하여보행속도는 4.2 km/h 의속도로자 159 연스런보행동작을수행하게하였으며, 3 회의시기를실시한후그평균값을통계처리자료로활용하 160 였다. 161 162 Table 2. Specifications of Force plate system Items Standard Plate size(inch) 15.75 23.62 3.94 Force range Fz(kN) 5-10 Shear force Fx, Fy(kN) 2.5-5 Natural Frequency Fz(Hz) 340-750 Natural Frequency Fz, Fy(Hz) 550-570 Weight(lb) 66 8
163 164 지면반력기는통제점틀중간에보행시흔들림이없도록고정시킨다음보행을하기위한연습용 고무매트를지면반력기위에고정시켰다 (Figure 3). 165 166 Figure 4. GRF axis coordinates 167 168 3. Data processing & Statistical analysis 169 170 171 본연구를통해얻어진원자료 (raw fate) 는통계적분석을위해 Window Spss Ver. 23.0 통계 프로그램을사용하여각각의아웃도어워킹화별로근피로도와지면반력을비교하기위해 기술통계분석과측정값탐색을통해평균 (M) 및표준편차 (SD) 를산출하였으며, 각변인값은 9
172 173 174 175 176 일원변량분석 (one-way ANOVA) 을실시하였다. 사후검증으로 Turkey 로개체간차이를검정하였으며, 통계적유의수준은 a=.05 로설정하였다. Results 1. 근피로도 177 178 179 180 181 182 183 184 185 다양한종류의아웃도어워킹화를신고트레드밀위에서 60 분동안시속 4.2km 의속도로보행한직후의근피로도변화량을분석한결과전경골근, 비복근, 외측광근, 대퇴이두근에서통계학적으로유의미한차이가있는것으로나타났다 (p<.01)<table 3>. 전경골근 (F 3 =4.818, p<.01) 에서는 Type C 의근피로도가가장낮게나타났으며, Type B, A, D 는유사한형태를나타냈다. 비복근 (F 3 =5.504, p<.01) 의사후검정에서근피로도의경우 Type C 가가장낮게나타났고, Type D, A 는유사한경향을보였으며, Type B 가가장높게나타났다. 외측광근 (F 3 =3.313, p<.05) 의근피로도는 Type A, C, B 순서로낮게나타났으며, Type D 가가장높게나타났다. 대퇴이두근 (F 3 =3.094, p<.05) 의근피로도는 Type C 가가장낮게나타났으며, Type D, B 는유사한결과가나타났으며, Type A 가가장높게나타났다 (Table 3). 186 187 Table 3. Comparision of muscle Fatigue in each outdoor walking shoes (unit: μv ) Item Type M±SD df F p Tukey Type A (n=30) 0.949±0.14 Tibialis anterior Gastrocnemius Vastus lateralis Type B (n=30) 0.953±0.12 Type C (n=30) 0.970±0.14 Type D (n=30) 0.940±0.13 Type A (n=30) 1.013±0.15 Type B (n=30) 0.995±0.12 Type C (n=30) 1.037±0.23 Type D (n=30) 1.030±0.23 Type A (n=30) 0.815±0.60 Type B (n=30) 0.810±0.27 Type C (n=30) 0.811±0.35 Type D (n=30) 0.749±0.33 3 4.818.002 C>B,A,D 3 5.504.001 C>D,A,B 3 3.313.019 A,C,B>D Biceps Type A (n=30) 0.960±0.66 3 3.094.026 C>D,B 10
femoris Type B (n=30) 0.971±0.16 C>A Type C (n=30) 0.993±0.19 Type D (n=30) 0.977±0.20 188 189 2. 지면반력 190 191 보행시하지관절의착지기와추진기의수직지면반력의값 Fz(+), 전후지면반력 Fy 의값은전 (+), 후 (-) 방향, 내외지면반력 Fx 의값은내 (-), 외 (+) 측방향의값이다. 192 193 1) 수직지면반력 194 아웃도어워킹화종류에따른보행시수직지면반력결과는 <Table 4> 와같이나타났다. 195 196 Table 4. Results of vertical ground reaction force in each shoes (unit : %BW) Item Type M±SD df F p A (n=30) 1.215±0.10 1 st Peak B (n=30) 1.239±0.07 C (n=30) 1.225±0.06 D (n=30) 1.224±0.07 3 0.484.694 2 nd Peak A (n=30) 1.210±0.08 B (n=30) 1.228±0.06 C (n=30) 1.221±0.04 D (n=30) 1.218±0.07 3 0.462.667 197 198 199 200 201 아웃도어워킹화종류에따른수직지면반력의제 1 정점은 Type B(1.239±0.07 %BW) 가가장높고, Type A(1.215±0.10 %BW) 가가장낮은것으로나타났으나, 평균값에서만차이를보였을뿐통계적으로유의한차이는나타나지않았다 (p>.05), 또한, 제 2 정점역시 Type B(1.228±0.06 %BW) 가가장높고, Type A(1.210±0.08 %BW) 가가장낮은것으로나타났으며평균값에서만차이를보였을뿐통계적으로유의한차이는나타나지않았다 (p>.05). 202 2) 전 후지면반력 11
203 204 205 206 아웃도어워킹화종류에따른보행시전후지면반력결과는 <Table 5> 와같으며, 브레이킹동작을나타내는제 1 정점을나타내는착지시 Type B(0.213±0.07 %BW) 가가장높은지면반력을나타냈고, Type A(0.223±0.06 %BW) 가가장낮은지면반력을나타냈지만통계적으로유의한차이는나타나지않았다 (p>.05). 207 Table 5. Results of anterior-posterior ground reaction force in each shoes (unit : %BW) Item Type M±SD df F p Anterior (+) Posterior (-) A (n=30) 0.208±0.05 B (n=30) 0.213±0.07 C (n=30) 0.212±0.04 D (n=30) 0.211±0.06 A (n=30) -0.223±0.06 B (n=30) -0.235±0.08 C (n=30) -0.232±0.09 D (n=30) -0.234±0.06 3 0.242.867 3 0.453.716 208 209 210 또한, 추진력을나타내는제 2 정점의경우 Type A(-0.223±0.06 %BW) 가가장낮은지면반력을 나타냈고, Type B(-0.235±0.08 %BW) 가가장높은지면반력을나타냈으나, 평균값에서만차이를 보였을뿐통계적으로유의한차이는나타나지않았다 (p>.05). 211 212 213 214 215 216 217 218 219 220 221 222 223 224 Discussion 본연구에서는사용자에게적합한아웃도어워킹화를선택할수있는기초자료를제공하고자아웃도어워킹화종류에따른근피로도와지면반력을비교분석하였다. 근피로도는운동으로야기된급성적인근육의힘발휘능력의저하를의미하며, 근피로의정도는수의적으로수축할수있는최대힘의감소량으로정량화되거나최대하의목표힘으로수축할때과업지속실패시간으로나타낼수있다 (Gandevia, 2001). 근전도를활용하여근피로도를산출하는데있어서 Normalized MPF 값을도출한근피로도산출결과 MPF 값이 1 보다작을수록근육의피로정도가높아지고 1 보다높은값을가지거나비교군보다높은값을가지면피로도가낮은것으로보고되어지고있다 (Kong et al., 2009; Park et al., 2010). 본연구결과전경골근의경우사후검정결과 Type C < Type B < Type A < Type D 순으로근피로도가높게나타났다. 비복근의경우사후검정결과 Type C < Type D < Type A < Type B 순으로근피로도가높게나타났다. 외측광근의 12
225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 경우사후검정결과 Type A < Type C < Type B < Type D 순으로근피로도가높게나타났다. 대퇴이두근의경우사후검정결과 Type C < Type D < Type B < Type A 순으로근피로도가높게나타났다. Type A 는지면으로부터발생하는지면반력을흡수하기위해인체에존재하는족궁의효율을높이기위하여내측과외측의경도를달리한다중경도형태의아웃솔과미드솔로설계되었다그결과체중부하기시 (loading responde) 경골의내회전과슬관절회외전에관여하는전경골근과대퇴이두근, 이지국면에서의추진력외에도발의좌우안정성에관여할수있는비복근의근피로도가비교적높게나타났으며, 효율적인충격흡수영향으로슬관절에서의충격흡수역할이감소함에따라외측광근에는비교적근피로도가낮게나타난것으로생각된다. Type B 는족궁을지지하기위하여아치지지구조물 (arch support) 의높이를조절가능하도록설계하였다. 그결과효과적인족궁지지로인하여전경골근의근파로는낮은경향을보였다. 그러나비복근, 외측광근, 대퇴이두근에서는비교적높은근활도를보임으로써효과적인족궁지지효과에대한추가적인검증이필요할것으로판단된다. Type C 의경우플라이핏폼 (Fly Fit Form) 을사용하여통기성향상은물론안창의디자인을충격흡수에효과적이도록설계되었다. 그결과보행을위한움직임이외에도입각기시발생하는충격량을흡수하기위한하지근육의역할이감소하게되고이에따라서전경골근, 비복근, 외측광근, 대퇴이두근에서비교적낮은근피로도를보였는것으로생각된다. Type D 는접지력향상을위해경도가높은암벽화용아웃솔을적용한신발이었다. 그결과체중부하기시전경골근에서충격흡수와발목관절의저측굴곡을조절하기위한근피로가증가한것으로여겨지며, 그에따라슬관절에서도충격량을감소시키기위한전략으로외측광근역시근피로가증가하는경향을보인것으로판단된다. 반면경도가높은영향으로인하여말기입각시의추진력에동원되는비복근의근활성은감소함으로써이에따라근피로가다소낮은경향이나타난것으로판단된다. 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 수직지면반력에대한선행연구결과를살펴보면 Byun(2010) 은수직지면반력을통한부하율을분석한결과, 제 1 정점은착지시발뒤꿈치가지면과접촉하면서일종의제동력역할을하며, 제 2 정점은이지기에앞으로나가기위해지면을차는힘에대한반력으로인체를이동하게만드는추진력역할을하는것으로보고했는데 (Lee & Sung, 2008), 본연구결과에서는모든아웃도어워킹화에서통계적으로유의한차이는나타나지않았으나, 보행시제어동작을수행하는제 1 정점과추진동작을수행하는제 2 정점에서 Type A 의신발이가장낮은수직지면반력을나타냈는데, 이러한결과는 Type A 의신발이지면반력을가장효과적으로흡수할수있는성능이우수한신발로판단된다. 또한전후지면반력에대한선행연구결과를살펴보면 Perry & Burnfield(2012) 는정상보행에서 Fy1( 제어기 ) 이체중의약 13% Fy2( 추진기 ) 는체중의약 23% 정도의크기를보인다고하였다. 본연구결과에서선행연구결과와유사하게보행시 4 종류의신발모두제어기의지면반력이추진기의지면반력에비해좀더높은지면반력을나타냈다. 모든신발에서제동시와추진시와유사한형태를나타냈으며, 그중내외측경도가다른 Type A 의신발이가장낮은전후지면반력을나타냈는데, 따라서 Type A 신발이지면반력을가장효과적으로수용할수있는우수한성능의신발로판단된다. 반면 Type B 는수직지면반력제 1 정점과제 2 정점, 전후지면반력제어기, 추진기모두높은경향의지면반력을보였는데, 이러한결과를유추해보면빠른보행속도로다이나믹한보행에알맞은아웃도어워킹화이면서, 아치높이조절을할수있는설계로인한충격부하를감소시켜줄수있는신발로여겨진다. 13
262 263 264 265 266 이상의연구결과를정리하면본연구에서수행했던하는아웃도어워킹화에대한분석이아웃도어워킹화의신발의기능을평가하고개선하는데활용될수있을것이라여겨지며아웃도워워킹화를기능성을개발하는데있어서기초자료로써그의의가있을것으로판단된다. 추후연구에서는본연구에서알아본근피로도와지면반력의관계가실제보행시하지관절에미칠수있는영향에대한세부적인연구가필요할것으로판단된다. 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 Conclusion 본연구에서는아웃도어워킹화유형에따른근피로도및지면반력의생체역학적변인들을비교분석하였다. 분석결과아웃도어워킹화유형에따라다음과같은결론을얻었다. 본연구에선정된유형별아웃도어워킹화의경우같은범주에속하는아웃도어워킹화군임에도불구하고, 아웃도어워킹화개발을위한설계시지향하고자하는목적에따라근피로도및지면반력결과값이다르게나타남을알수있었다. 근피도로가낮다고반드시지면으로부터발생하는충격을흡수하는데있어서긍정적이라고볼수없었으며, 근피도도가높다고해서지면반력을흡수하는능력이부정적이라고볼수없었다. 그러므로동일한제품군의신발개발이라하더라도기능적목적및특성에따라소재, 물성, 경도, 구조적설계, 구조체형태, 등의조합을고려하여개발되어야기능적목적에도달하는신발을제작할수있을것으로판단된다. 추후연구에서는실제아웃도어환경에서아웃도어워킹화의기능적검증에대한연구가필요할것으로여겨지며또한아웃도워워킹화종류에따른근피로도와지면반력의관계가실제보행시하지관절에미칠수있는영향에대한세부적인연구가필요할것이다. 282 283 284 285 286 287 288 289 290 291 292 293 294 295 Reference Byun, K. S. (2010). Biomechanical Analysis of Different Outsole types of Functional Walking Shoes, Unpublished Master s Thesis, Graduate School of Sungkyunkwan University. Chae, W. S., Jung, J. H., & Lee H. S. (2012). Biomechanical analysis of wearing carbon Nanotube-based insole during drop landing. Korean Journal of Sport Biomechanics, 22(4), 429-435. Choi, K. J. & Kwon, H. J. (2003). Sport biomechanical comparative analyses between general sporting shoe and functional walking shoe. Korean Journal of Sport Biomechanics, 13(2), 161-173. Elizabeth, E. M., Katherine, K. W., Daniel, E. L., Heather, L. N., Rachael, E. D. (2014). The effect of minimal shoes on arch structure and intrinsic foot muscle strength. Journal of Sport and Health Science, 3, 74-85. Jang, H. J. (2008). An Influence of Reactive Force on Ground in Walking by Koreandance Execute, Unpublished Master s Thesis, Graduate School of HanYang University. 14
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