선자세및보행시가방형태와무게변화에따른족저압비교 The Journal Korean Society of Physical Therapy 공원태, 이상열 1, 김중휘 2 구미 1 대학물리치료과, 1 김해대학물리치료과, 2 강병원물리치료실 Comparison of Foot Pressures in Stance and Gait as a Function of Type of Bag Carried and of Changing of Weight Won-Tae Gong, PT, PhD; Sang-Yeol Lee, PT, MS 1 ; Joong-Hwi Kim, PT, PhD 2 Department of Physical Therapy, Gumi College; 1 Department of Physical Therapy, Kimhae College; 2 Department of Physical Therapy, Kang Hospital Purpose: Our study sought to investigate differences in plantar foot pressure as a function of type of pack carried and of changing weight during gait and stance. Methods: Subjects were 40 students with no disabilities. Plantar foot pressure was measured with different types of packs carried and with changing weight of the pack during both gait and stance and while changing feet. During stance while carrying a satchel on the shoulder caused a disproportionate change in plantar foot pressure. An even great imbalance occurred for plantar foot pressure during gait. Results: Using a satchel can influence diseases such as scoliosis that are caused by unbalanced muscle activation and by a disproportionate distribution of the weight of the body. Conclusion: Knowing how to use a pack correctly and how to appropriately adjust the weight of bag should be taught. Keywords: Plantar foot pressure, Type of bag, Changing weight 논문접수일 : 2010년 1월 21일수정접수일 : 2010년 3월 21일게재승인일 : 2010년 4월 1일교신저자 : 김중휘, ibobath@hanmail.net I. 서론가방을메고보행을할경우인체에는가방의무게에의해신체적스트레스가가해지고, 생리적으로또는역학적으로영향을받아동적균형과자세에변화가나타난다. 1-3 성인이 22.5 kg의배낭을등에짊어졌을때정상적인분절간움직임에변화가발생하였음을보고한바있다. 4 인간은한쪽에무게가가해지면무의식적으로자신의팔을옆으로들어올리거나동체를무게가가해진반대쪽으로기울여서외적인부하에대해평형을취해중심선을기저면중앙에위치시키려한다. 하지만가방의무게가너무무겁거나, 가방의형태나휴대방식, 가방의위치가불량하여무게를분산시키지 못할경우에비정상적인자세를유발하고, 근골격계에영향을주어통증과척추장애를유발할수있다. 3 따라서물건을나를때무게의위치에따라인체의분절은비대칭적으로정렬을한다. 어깨에가해지는일측성부하를통해몸통과골반의움직임에미치는영향을삼차원운동학적측면에서분석한결과가방을옆으로메고걸었을때무게가실린반대쪽으로유의하게증가하는것을볼수있다. 5 부적절한보행동작은발과지면의접촉시발생하는충격을적절히흡수하지못해인체의근골격계에과도한피로를유발시켜부상을야기시킬수있다. 6,7 바르지않은자세의보행패턴은생리학적장애를가져와근육과관절에피로를주며, 척 선자세및보행시가방형태와무게변화에따른족저압비교 1
J Kor Soc Phys Ther 2010;22(2):1-6 추에반복적인비정상충격을전달하여척추질환의직접적인원인이되기도한다. 8 이런부적절한무게중심의변화와충격을연구하기위해족저압을측정하였는데족저압은인체의균형정도에반영하는하나의지표로서, 운동과학의임상분야, 연구분야에서많은관심을갖고있는측정대상중하나이며, 9 족저압력분포의측정을통해서발의각부위에전달되는충격을자세하게평가할수있을뿐만아니라, 이러한압력분포의측정과분석을통하여부상의진단및치료에도이용될수있다. 10 최근청소년들에서요통이나어깨통증, 경부통등의호소와척추측만증, 후만증및전만증과같은척추변형발생률이증가하고있고, 11 가방의무게나형태에따른사회적관심도는높아지고있다. 하지만기존의연구들이가방을메었을때산소소모량비교, 12,13 보행분석, 14 근전도분석, 15 무게분산에따른효과, 16 발의비례추진력 17 에대한연구가이루어지고있으며, 또한일측성부하는에너지소비 12,16 에대한연구만있을뿐어깨가방과등가방의비교에대한연구는거의없는실정이다. 따라서본연구는사람들이가방을착용하는가장흔한형태인어깨가방과등가방에서의족저압을비교하여어떤가방메기방법이인체에덜해로운가를알아보는데있다. 3. 실험절차및방법본연구에서는가방을메는방법에따라등가방을맨그룹과오른쪽어깨에어깨가방을맨두그룹으로나누어실험을실시하였다. 각각그룹은가방을메지않은상태와가방의무게를 2, 5, 10, 15 kg로주었을때, 총 5가지경우에 stance, gait의족저압을제 1지절간관절 (p1), 제 1 중족지절관절 (p2), 제 2 중족지절관절 (p3), 제 3 중족지절관절과제 4 중족지절관절중간점 (p4), 제 5 중족지절관절 (p5), 입방골 (p6), 종골 (p7) 의 7개지점에서측정하였다 (Figure 1). II. 연구방법 1. 연구대상본연구는 D대학에재학중인학생들중실험에대해충분히설명을듣고이연구에참여하고자자발적으로서면동의서를제출한남 녀각각 20명씩 40명의건강한학생들을연구대상자로선정하였으며제외기준은정상적인보행에영향을줄정형외과적, 신경외과적인질환이있거나, 기능적, 해부학적인하지길이차이가있거나, 주3회이상의규칙적인운동을행하는자는제외하였으며대상자의그룹별분류는무작위로진행되었다. 2. 측정도구양발로선자세시그리고보행시입각기의한발지지기동안발에서의족저압을측정하기위하여 Zebris FDM-T Treadmill (Zebris, 독일 ) 을이용하였다. FDM-T Treadmill 은센서가부착된 Treadmill과자료를전송받아분석하는소프트웨어로이루어져있고조작이쉬우며신발을벗거나신었을때뿐만아니라좌 우발의입각기, 압력중심, 압력분포, 힘등을자동으로분석한다. Figure 1. 7 area of foot plantar pressure. 선자세시의측정은 Winter 18 가정적압력중심을측정할때초기 20초간의자료는분석대상에서제외하는것이일반적이라하여본연구에서도위의실험장비가선자세측정시간이 10초로정해져있기때문에 30초동안측정하여 20초는기록하지않는방식을적용하였으며, 시선은정면을향하게하고양팔은편안하게유지하도록하였다. 보행에서의측정은보행을하기전가방의무게에익숙한보행을이끌어내기위해측정전 5분정도를걷게하였으며, 피실험자의시선은정면을향하게하고양팔은가볍게흔들것을지시하였다. 선자세시및보행시족저압측정중피실험자의동요를방지하기위해레코딩의시작과끝은대상자에게알리지않았다. 그리고트레드밀에대한거부감을줄이기위해양말을신게하였으며긴바지는발목까지밑단을걷어올려기록에방해가되지않게하였다. 위와같은방법으로실험대상자 1명당 1가지의가방형태로무게를달리하여총선자세측정 5회, 보행측정 5회씩실시하였으며, 피로감을줄이기위해가방의무게를높일때마다 2분간의휴식시간을주었다. 또보행의속도는개인차를감안하여 2.5 km/h로하였다. 2 Comparison of Foot Pressures in Stance and Gait as a Function of Type of Bag Carried and of Changing of Weight
공원태, 이상열, 김중휘 Table 1. The comparison of the foot plantar pressure on stance with back pack (Unit: N/cm 2 ) Rt p1 2.04±1.99 2.43±1.84 2.13±1.60 2.73±2.14 3.19±2.14 1.03 0.42 Rt p2 4.46±2.33 4.71±2.84 5.14±2.88 5.16±3.71 5.54±3.91 2.04 0.13 Rt p3 6.49±2.15 6.46±1.60 6.36±1.85 6.56±1.84 6.04±2.17 0.87 0.48 Rt p4 5.73±1.53 5.74±1.41 5.61±1.80 5.76±1.84 5.56±2.06 0.31 0.86 Rt p5 3.81±1.73 3.79±1.95 3.63±1.94 4.18±2.38 3.78±2.25 1.13 0.34 Rt p6 2.63±2.13 2.71±2.04 2.56±2.38 2.89±2.50 2.74±2.23 0.41 0.79 Rt p7 10.71±4.04 11.09±4.43 11.81±4.89 12.61±5.03 14.36±5.52 15.88 0.00* Lt p1 2.31±1.91 2.63±2.37 2.48±1.89 2.94±2.33 3.18±2.07 1.90 0.15 Lt p2 4.63±3.59 5.06±4.00 5.38±4.14 5.88±5.65 5.89±4.29 3.44 0.03* Lt p3 5.78±1.90 6.06±1.61 6.11±1.78 6.29±1.77 6.31±1.49 0.80 0.52 Lt p4 5.66±2.12 5.36±1.79 5.31±1.63 5.78±1.79 5.21±1.57 1.25 0.29 Lt p5 3.98±2.83 4.09±2.63 3.61±2.60 3.94±2.85 3.39±1.99 0.48 0.74 Lt p6 2.63±2.37 2.84±2.38 2.56±2.14 3.05±3.63 2.53±2.44 0.62 0.65 Lt p7 10.09±3.68 10.44±4.11 11.36±4.32 11.98±5.00 13.94±5.86 5.97 0.00* Mean±SD * Statistically significant with p<0.05 4. 자료분석자료처리는 SPSS(window version 12.0) 으로하였으며가방무게에따른족저부의각영역별족저압유의성을알아보기위하여반복측정분산분석을하였으며대상자의특성에대한동질성검정에서성별은카이스퀘어검정으로연령, 신장, 체중은독립표본 T검정으로하였으며, 유의수준 α는 0.05로하였다. III. 결과 1. 연구대상자의일반적특성본연구에참여한대상자는총 40명으로연령은 19세에서 27세이었으며평균연령은 21.00±0.29( 평균 ± 표준오차 ) 세이었으며, 평균신장은 166.22±2.89 cm이었고, 평균체중은 64.45±3.35 kg이었다. 신장, 체중에대한독립표본 t-검정에서통계적으로유의한차이는없었으나 (p>0.05) 연령에대한차이는있었다 (p<0.05). 따른유의성이있었고, 좌측족저의각영역별압력비교에서는 p2, p3, p7부위에서등가방의무게에따른유의성이있었다 (Table 2). 4. 어깨가방착용후선자세시무게에따른족저압비교어깨가방착용후선자세시무게에따른우측족저의각영역별압력을비교한결과 p2, p3, p7부위에서어깨가방의무게에따른유의성이있었고, 좌측족저의각영역별압력비교에서는 p3 부위에서어깨가방의무게에따른유의성이있었다 (Table 3). 5. 어깨가방착용후보행시무게에따른족저압비교어깨가방착용후보행시무게에따른우측족저의각영역별압력을비교한결과 p1, p3, p6, p7부위에서어깨가방의무게에따른유의성이있었고, 좌측족저의각영역별압력비교에서는 p1, p2, p3, p5, p7부위에서어깨가방의무게에따른유의성이있었다 (Table 4). 2. 등가방착용후선자세시무게에따른족저압비교 등가방착용후선자세시무게에따른우측족저의각영역별압력을비교한결과 p7부위에서등가방의무게에따른유의성이있었고, 좌측족저의각영역별압력비교에서는 p2와 p7부위에서등가방의무게에따른유의성이있었다 (Table 1). 3. 등가방착용후보행시무게에따른족저압비교등가방착용후보행시무게에따른우측족저의각영역별압력을비교한결과 p1, p3와 p7부위에서등가방의무게에 IV. 고찰신체무게중심의위치는어떠한움직임에대해서도항상변화한다. 신체는무게중심을항상바닥에서수직축상에유지하려고하는조절기능을가지고있다. 어떤짐을들고이동할때무게중심은물건을옮길때마다자동으로균형을유지하며이동한다. 이러한자율적인자세조정은두가지기전에의하여이루어지는데, 첫째는상체의재정렬을통해서이고, 둘째는바닥에 선자세및보행시가방형태와무게변화에따른족저압비교 3
J Kor Soc Phys Ther 2010;22(2):1-6 Table 2. The comparison of the foot plantar pressure on gait with back pac (Unit: N/cm 2 ) Rt p1 7.23±3.98 6.91±4.74 7.10±5.13 7.87±4.84 9.12±5.70 3.89 0.00* Rt p2 6.52±2.65 6.96±3.18 7.10±2.87 7.90±3.57 8.39±4.13 1.85 0.16 Rt p3 8.84±2.07 9.68±2.41 9.77±2.03 10.19±2.35 10.79±2.36 4.45 0.01* Rt p4 8.40±2.53 8.12±2.55 8.24±2.53 8.69±2.50 8.84±2.54 2.05 0.13 Rt p5 7.41±2.35 6.98±2.91 7.18±2.55 7.11±2.12 7.46±2.70 0.74 0.57 Rt p6 6.66±2.74 7.10±3.38 7.75±4.14 8.16±4.52 7.76±3.26 2.40 0.09 Rt p7 13.15±2.49 13.98±2.83 13.96±2.79 15.07±2.94 16.01±2.77 10.98 0.00* Lt p1 6.43±3.74 6.85±3.00 6.63±3.48 7.54±3.60 8.12±3.63 1.06 0.40 Lt p2 7.34±4.40 7.89±4.27 8.33±4.67 8.97±6.00 9.43±5.87 4.00 0.01* Lt p3 8.79±2.35 9.38±2.56 9.76±2.33 10.30±2.49 11.31±2.31 7.86 0.00* Lt p4 7.68±2.04 7.65±2.19 7.84±2.14 8.09±2.44 8.78±2.41 1.85 0.16 Lt p5 7.00±2.45 6.53±2.09 6.70±2.02 6.40±1.52 6.92±1.78 2.11 0.12 Lt p6 6.35±2.83 6.21±2.41 7.12±4.53 7.51±5.10 7.81±5.66 0.63 0.64 Lt p7 13.88±3.34 14.60±2.96 14.81±3.28 16.08±3.59 16.59±3.85 0.43 0.04* Mean±SD * Statistically significant with p<0.05 Table 3. The comparison of the foot plantar pressure on stance with shoulder pack (Unit: N/cm 2 ) Rt p1 2.58±2.63 2.19±2.23 2.93±2.46 3.24±2.98 3.13±1.97 1.88 0.16 Rt p2 5.08±2.35 4.84±2.31 5.26±3.17 5.51±3.02 6.04±3.53 3.10 0.02* Rt p3 6.46±2.34 6.06±2.17 7.03±2.72 7.23±3.00 7.01±2.82 3.36 0.03* Rt p4 5.81±1.95 5.51±1.67 5.73±1.73 6.11±1.62 5.91±1.45 2.64 0.07 Rt p5 3.86±1.79 3.38±1.97 3.38±1.86 3.33±1.86 3.78±2.10 2.23 0.11 Rt p6 2.90±2.11 2.59±1.87 2.79±1.71 3.09±1.98 3.71±2.37 1.15 0.37 Rt p7 10.14±3.89 11.89±4.71 13.14±5.17 16.06±6.83 19.51±8.15 15.37 0.00* Lt p1 2.04±2.00 1.78±1.89 2.18±2.03 1.98±1.73 0.89±1.53 3.01 0.05 Lt p2 4.08±3.62 4.48±3.57 3.79±3.25 3.34±3.49 2.83±2.79 2.79 0.06 Lt p3 6.01±2.77 5.64±1.98 5.39±2.65 4.93±2.65 4.31±2.53 6.78 0.00* Lt p4 5.58±2.76 5.23±1.83 5.33±2.17 4.84±2.26 4.11±2.19 2.84 0.06 Lt p5 3.68±1.80 3.54±1.48 3.13±1.56 3.73±2.66 3.34±2.08 2.07 0.13 Lt p6 2.14±1.85 2.29±1.58 2.11±1.78 2.38±2.51 1.78±1.81 1.97 0.14 Lt p7 11.01±4.12 11.43±3.71 11.44±4.18 10.28±2.87 11.56±5.54 1.23 0.30 Mean±SD * Statistically significant with p<0.05 Table 4. The comparison of the foot plantar pressure on gait with shoulder pack (Unit: N/cm 2 ) Rt p1 5.38±53 5.77±82 5.98±32 6.60±42 8.21±90 4.73 0.00* Rt p2 7.36±42 7.83±54 7.85±42 8.66±59 8.44±23 2.40 0.06 Rt p3 9.73±68 9.92±51 10.43±223 10.93±19 11.42±38 4.00 0.02* Rt p4 8.50±27 8.33±11 8.47±89 8.65±41 8.68±42 0.53 0.71 Rt p5 6.15±51 5.83±31 5.80±97 5.98±19 6.12±12 0.79 0.54 Rt p6 6.80±09 6.70±17 7.12±84 7.52±69 8.56±57 5.83 0.00* Rt p7 13.50±50 14.34±08 14.34±27 14.88±53 15.41±64 6.84 0.00* Lt p1 5.62±96 5.70±20 6.42±42 8.08±64 9.86±54 7.20 0.00* Lt p2 7.73±59 8.49±43 8.51±26 10.29±13 10.42±13 4.60 0.01* Lt p3 9.65±66 10.15±29 10.26±46 9.85±29 10.85±37 7.59 0.00* Lt p4 7.93±54 8.25±68 8.13±72 7.75±06 8.23±51 0.54 0.70 Lt p5 5.61±91 5.88±17 5.91±51 5.59±19 6.42±41 2.99 0.02* Lt p6 5.76±50 5.62±36 6.18±82 6.23±51 6.35±32 1.52 0.20 Lt p7 14.40±75 15.42±10 15.71±01 16.72±99 17.66±20 8.72 0.00* Mean±D *: Statistically significant with p<0.05 4 Comparison of Foot Pressures in Stance and Gait as a Function of Type of Bag Carried and of Changing of Weight
공원태, 이상열, 김중휘 디디는압력중심의변화를통해서이다. 한쪽손에짐을들면신체는바닥에서무게중심의위치를좀더중앙의수직축으로이동시키기위하여척추를한쪽으로굽히면서몸통, 팔, 머리등의상체를짐의반대편으로이동시킨다. 무게중심을수직축으로접근시키기위하여신체를재정렬하는것이다. 만약에짐을한쪽으로만들고이동한다면신체는무게중심을중앙으로가져가기위하여척추를더많이옆으로굽혀야한다. 이러한상태는짐이더무거울수록, 짐이몸의중심에서더멀리위치할수록더심해진다. 마찬가지로, 자세정렬을위하여근육들은더많은운동에너지를필요로한다. 특히골격구조의변화가심한사춘기때의이러한스트레스는척추측만증을야기할수도있다. 또한뒤쪽으로지나치게무거운가방을멜경우상대적으로목이앞쪽으로쏠리는거북목증후군을유발할수있다. 본연구에서는가방휴대방법과무게에따른족저압변화양상을토대로보행에서의균형을알아보기위해 back bag을맨그룹과어깨가방을맨그룹두분류로나눠서실험을하였다. 가방의무게는 0, 2, 5, 10, 15 kg으로주었다. 족저압측정시압력중심의전, 후, 내, 외측이동에대한특징은균형능력을해석하는중요한변수로써, 족저압분포의변화를반영한다. 보행시입각기동안에족저압중심 (COP) 의이동경로를관찰하면피검자의균형이나보행패턴등을평가할수가있다. 19 Jo 20 는가방의무게가증가함에따라보폭도유의하게커진다고하였다. 본연구에서는측정지표로족저압만을다루었기때문에보폭의변화는알수없으나 back bag 착용시 10 kg 에서 15 kg의무게변화가이루어졌을때의족저압의차이가 5 kg에서 10 kg의무게변화가이루어졌을때의족저압의차이보다작은것으로보아가방의무게로인한불균형이나타나는무게는 5 10 kg사이라고할수있겠다. 어깨가방적용시에는 5 kg의무게에도좌우측족저의불균형이유의하게나타났다. 어깨가방이등가방보다적은무게로인체의불균형을나타내는것으로보인다. Crowe와 Samson 21 에따르면가방의무게가몸무게의최대 15% 가넘지않아야무게분산이효과적으로이루어진다고하였다. Park 19 은체중의 15% 정도의일반적인무게인 0.5 kg, 1 kg, 1.5 kg, 2 kg, 2.5 kg, 3 kg, 3.5 kg, 4 kg로가방에무게차이를주어족저압의변화를관찰한결과발의특정영역에서압력증가, 족저압과힘-시간적분값, 비례추진력의조건간차이가유의하게나타나기는했지만공식화하기에는무리가있을정도로불규칙적으로나타났으며, 좌우측발사이의비대칭적변화도뚜렷하게나타나지않음을관찰하였다. 위연구에서가방의무게를인체가무게분산을효과적으로할수있는체 중의 15% 이하무게만을적용하였다는것에착안하여본연구에서는가방의무게분산이효율적으로나타나지않는경우에초점을두어 15% 이하와 15% 이상의무게를가방에적용해실험을진행하였다. 본연구도위의 Park 19 의연구결과와같이등가방을메고선자세시와어깨가방을메고선자세시가방의무게변화에따라특정지점에서족저압이유의함을가지며증가하였다. 이것은가방의무게가인체의후방또는측방에부하를증가시켰기때문이며어깨가방을메고선자세시에는가방을메지않은쪽의족저압이줄어들었고등가방을메고선자세시에는전족부의족저압의줄어들지않았다. 여기서가방의무게증가는인체족저압의불균형을나타내지만등가방보다어깨가방에서현저하게나타나는것을알수있다. Han 등 22 은성인의평지보행시압력중심이동경로는발뒤꿈치에서부터시작해전족부를거쳐엄지발가락으로이동하는것을관찰하였다. 이는정상보행시의한발지지기시족궁내를제외하고족저압이가장크게나타나는지점들과일치한다. 본실험에서의등가방을메고보행시와어깨가방을메고보행시에서도족저압력중심의이동경로가통과하는지점에서가방의무게에따른족저압의변화가유의하게나타났으나어깨가방을메고보행시우측족저의외측지점과좌측족저의외측지점에서무게변화에따른족저압의유의함이보였다. 전자는가방을오른쪽어깨에메었기때문에가방의무게에따른부하증가에의한것으로보이며후자는보행시반대측 ( 가방을맨측 ) 의하강을방지하고압력중심이족부내에위치하도록하기위한보상작용이나타난것으로생각된다. 본연구를통해서등가방보다는어깨가방에서무게에따른족저압의차이가크고또한선자세시보다보행시더큰차이가있었기에보행시 5 kg 이상의무게를운반시등가방보다는어깨가방을이용하는게바람직함을알수있었다. 하지만가방의형태와무게에따른좌 우족저압의차이를알아보지못한것은본연구의제한점이라할것이며향후가방의형태와무게에따른좌 우족저압의차이뿐만아니라측만증과같은구조적기능적문제를내포한환자들을대상으로도연구가진행되었으면한다. V. 결론본연구의결과에따르면등가방과어깨가방을착용하였을때무게에따라정도에차이가있을뿐두가지가방형태모두족저압에변화를일으킨다. 즉, 인체의무게중심점의이동에큰영향을주지않는무게라면큰문제가되지않지만무게중심점의이동을현저히유발시키는가방의무게는인체의변형 선자세및보행시가방형태와무게변화에따른족저압비교 5
J Kor Soc Phys Ther 2010;22(2):1-6 을초래할수있다. 또한선자세시보다보행시에는하지가속도의영향으로더많은변화를보인다. 그리고과도한무게의어깨가방을착용하면등가방을착용하였을때보다작은가방무게로도무게중심점이크게이동하고인체에서관찰되지않는측만증이나타날수있어어깨가방은피해야할것이다. 앞으로의연구에서는다양한착용법을제시하고무게변화를개개인의몸무게에대한비율을사용하여부하를가하고다양한측정도구로가방휴대방법에따른인체의변화를다각도로관찰하는것이필요할것으로생각한다. Author Contributions Research design: Gong WT Acquisition of data: Lee SY Analysis and interpretation of data: Gong WT Drafting of the manuscript: Lee SY Research supervision: Kim JH 참고문헌 1. Kim CK, Shin DM. Kinematic analysis of book bag weight on gait cycle and posture of youth. Journal of sport and leisure studies. 1995;3(1):175-85. 2. Oh JH, Choi SN. Effects of the length of schoolbag string on gait posture. Journal of Sport and Leisure Studies. 2007;30:619-29. 3. Matsuo T, Hashimoto M, Koyanagi M et al. Asymmetric load-carrying in young and elderly women; Relationship with lower coordination. Gait Posture. 2008;28(3):517-20. 4. Vacheron JJ, Poumartat G, Chandezon R et al. Changes of cotour of the spine caused by load carrying. Surg Radiol Anat. 1999;21(2):109-13. 5. An JS. The effects of asymmetric load of shoulder bag on trunk and pelvis movement patterns of normal adult during gait. Yonsei University. Dissertation of Master s Degree. 2006. 6. Lee SY, Bae SS. The studies on the foot stability and kinesiology by direction of carry a load during gait. J Kor Soc Phys Ther. 2009;21(2):97-101. 7. Nigg BM, Bahlsen HA, Luethi SM et al. The influence of running velocity and midsole hardness on external impact forces in heel-toe running. J Biomech. 1987;20(10):951-9. 8. Holewijn M. Physiological strain due load carrying. Eur J Appl Physiol. 1990;61(3-4):237-45. 9. Lee SY, Chang JS, Lee MH. The effects of plantar foot pressure and EMG activation of neck, lumbar and low limbs by using carrier during walking. Korean Journal of Sport Biomechanics. 2009;19(2):237-44. 10. Lee JS, Kim YJ, Park SB. A study of in-sole plantar pressure distribution in functional tennis shoes. Korean Journal of sport Biomechanics. 2004;14(3):99-118. 11. Lee EJ, Kang YS, Kim KH et al. The investigation of spinal deformity in Korean elementary school students. The Journal of Korean Academy of Refabilitation Medicine. 2004; 28(1):83-7. 12. Evans OM, Zerbib Y, Faria MH et al. Physiological response to load holding and load carriage. Ergonomics. 1983;26 (2):161-71. 13. Kirk J, Schneider DA. Physiological and perceptual response to load carrying in female subjects using internal and external frame backpack. Ergonomics. 1992;35(4):445-55. 14. Bloom D, Woodhull-Mcneal AP. Postural adjustments while standing with two types of loaded backpack. Ergonomics. 1987;30(10):1425-30. 15. Bobet J, Norman RW. Effects of load placements on back muscle activity in load carriage. Eur J Appl Physiol Occup Phyol. 1984;53(1):71-5. 16. Legg SJ, Mathantry A. Comparison of five modes of carring a load close to the trunk. Eegonomics. 1985;28(12):1653-60. 17. Park SJ, Kim MH, Kim JS. Changes of relative impulse of foot on carrying 5 types of schoolbag during level walking. J Kor Soc Phys Ther. 2009;21(3):61-8. 18. Winter DA. Human balance and posture control during standing and walking. Gait Posture. 1995;3(4):193-214. 19. Park SJ. The analysis the changes of foot pressure by various carrying a pack methods during walking. Daegu University. Dissertation of Master s Degree. 2008. 20. Jo SC. Effects of backpack weight on elementary school boy s walking. The Korean Journal of Sports Medicine. 2001;19(2):303-10. 21. Crowe A, Samson MM. 3-D analysis of gait: The effects upon symmetry of carrying a load in one hand. Human Movement Science. 1997;16(2-3):357-65. 22. Han JT, Kim K, Lim SG. Comparison of plantar foot pressure and shift of COP among level walking stairs and slope climbing. Korean Journal of Sport Biomechanics. 2008;18 (4):59-65. 6 Comparison of Foot Pressures in Stance and Gait as a Function of Type of Bag Carried and of Changing of Weight