pissn Vol. 31, No. 1, February 2019 J Kor Phys Ther 2019:31(1):1-6 1229-0475 eissn 2287-156X Original Article Comparison of the muscle activity in the normal and forward head postures based on the pressure level during cranio-cervical flexion exercises Donghoon Kang, Taeyoung Oh Department of Physical Therapy, Silla University, Busan, Korea Purpose: This paper proposes proper and effective neck exercises by comparing the deep and superficial cervical flexor muscle activities and thickness according to the pressure level during cranio-cervical flexion exercises between a normal posture group and forward head posture group. Methods: A total of 20 subjects (8 males and 12 females) without neck pain and disabilities were selected. The subjects craniovertebral angles were measured; they were divided into a normal posture and a forward head posture group. During cranio-cervical flexion exercises, the thickness of the deep cervical flexor neck muscle and the activity of the surface neck muscles were measured using ultrasound and EMG. Results: The results showed that the thickening of the deep cervical flexor was increased significantly to 28 and 30 mmhg in the forward head posture group. The sternocleidomastoid muscle activity increased significantly to 24, 26, 28, and 30 mmhg in the forward head posture group. The anterior scalene muscle activity increased significantly to 26, 28, and 30mmHg in the forward head posture group. A significant difference of 26, 28, and 30 mmhg in the sternocleidomastoid and anterior scalene muscles was observed between two groups. Conclusion: To prevent a forward head posture and maintain proper cervical curve alignment, the use of the superficial cervical flexor muscles must be minimized. In addition, to perform a cranio-cervical flexion exercises to effectively activate the deep cervical flexor muscles, 28 and 30 mmhg for normal posture adults and 28 mmhg for adults with forward head postures are recommended. Keywords: Posture, Neck muscles, Craniocervical, Exercises 서론근골격계질환에서목통증은현대인들에게가장흔하게발생하는질환으로알려져있다. 1 인구의 67% 가일생에한번이상경험하게되고, 유병률은연구마다 29-76% 까지다양하게보고된다. 2 목통증의원인으로는머리를고정하기위해오랜시간목근육의수축이지속되어야하므로목근육의약화로인한피로의누적, 잘못된자세나습관으로인하여역학적인통증 (mechanical pain) 으로발생한다. 3-6 정상적인머리자세는귀구슬 (tragus) 과봉우리각 (acromial angle) 이수직선상에놓여있는반면, 앞쪽머리자세 (forward head posture) 는바로선자세에서귀구슬과봉우리각사이의수평거리가 5 cm 이상이고, 아래쪽목뼈의굽힘과위쪽목뼈의과도한폄을동반하는자 세이다. 7 여러선행연구에서앞쪽머리자세에따른다양한변화들을다루었는데, Yip 등 8 은, 앞쪽머리자세를가지고있는대상자들은정상적인자세를가지고있는대상자들보다목통증이증가하였음을보고하였고, 목의얕은목굽힘근인목빗근 (sternocleidomastoid muscle) 과앞목갈비근 (anterior scalene muscle) 등의과도한활성화로인해깊은목굽힘근 (deep cervical flexor) 의활동이억제되어, 9 목뼈관절의안정성이결여되는결과를유발한다. 10 최근올바른목뼈의자세조절을위하여깊은목굽힘근의역할의중요성과활성도를증가하는방법에관한연구들이많이보고되고있다. 그중, 머리- 목굽힘운동 (cranio-cervical flexion exercise) 은목빗근, 앞목갈비근과같은얕은목굽힘근들의사용을최소화하고, 깊은목굽힘 Received Jan 2, 2019 Revised Feb 17, 2019 Accepted Feb 27, 2019 Corresponding author Taeyoung Oh E-mail ohtaeyoung@silla.ac.kr Copylight 2019 The Korean Society of Physical Therapy This is an Open Access article distribute under the terms of the Creative Commons Attribution Non-commercial License (Http:// creativecommons.org/license/by-nc/4.0.) which permits unrestricted non-commercial use, distribution,and reproduction in any medium, provided the original work is properly cited. www.kptjournal.org 1
The Journal of Korean Physical Therapy Donghoon Kang, et al. 근인목긴근, 머리긴근의활성도를증가시키는운동으로써환자또는건강한사람을대상으로임상에서주로사용되고있다. 11 하지만여전히머리-목굽힘운동에관한연구는부족한실정이다. 앞선연구들에서는목의자세에따른머리-목굽힘운동시깊은목굽힘근과얕은목굽힘근들의활성도에대한비교와깊은목굽힘근을활성화하고얕은목굽힘근을최소한으로사용되는적절한압력정도를제시하기에는부족하였다. 따라서본연구의목적은선행연구의부족한실정을보완하여통증에따른머리-목굽힘운동시근활성도정도차이가아닌자세에따른깊은목굽힘근과얕은목굽힘근들의활성화정도를살펴보기위해머리-목굽힘운동시압력에따라정상자세와앞쪽머리자세를가진성인의깊은목굽힘근과얕은목굽힘근의활성도를비교분석하여머리-목굽힘운동시올바르고효과적인압력의정도를제시하고자한다. 연구방법 1. 연구대상본연구의대상자는부산소재의 20-30대남녀성인을대상으로하여목과관련하여시각통증등급 0점, 목장애지수 0에서 4점사이인건강한성인 20명 ( 남자 8명, 여자 12명 ) 을선정하였다. 다른질환에의한심각한손상이나신경학적질환이있는자, 수술을받은경험이있는자, 최근 3개월이내목뼈관절의치료이력이있는대상자는연구에서제외하였다. 대상자는실험에앞서실험에관한절차와방법에대한설명을충분히한후자발적으로실험동의서를작성한후, 본연구에참여하였다 (Table 1). 력바이오피드백기구를사용하였다. 압력바이오피드백기구는공기주머니, 압력표시계, 공기펌프로구성되어있는데, 근육의수축으로발생된힘이공기주머니에압력을가하여, 압력정도가압력표시계에수치로나타내어근육의수축력정도를측정할수있다. 12 2) 표면근전도 (Surface electromyograph) 본연구에서는머리-목굽힘운동을수행하는동안얕은목굽힘근들의근활성도를측정하기위해표면근전도측정장비인 2EM (4D-MT, Relive, Korea) 을사용하였다. 3) 초음파영상장치 (Ultra Sonic Imaging) 본연구에서는머리-목굽힘운동을수행하는동안깊은목굽힘근의목긴근두께변화를측정하기위하여초음파영상장치 (IE33, Philips medical systems, Germany) 를사용하였다. 초음파는근골격계검사에서근육의활성패턴을측정하기위하여근육의두께를측정할수있으며, 선택적으로깊은근수축훈련과근육의위축비대, 생체되먹임을통한훈련방법의교육및수정등을할수있는장비이다. 13 3. 실험절차 1) 머리-척추각 (Cranio-vertebral angle) 측정머리-척추각은앞쪽머리자세를평가하기위해사용되는검증된방법이다. 14 측정을위해대상자의일곱번째목뼈가시돌기위에표식 2. 측정도구 1) 압력바이오피드백 (Pressure biofeedback unit) 대상자들의머리 - 목굽힘운동시수축을일정하게측정하기위해압 Table 1. Demographic characteristics of subjects in each group FHP (n=10) NHP (n=10) t p Gender Male 4 4 Female 6 6 Age (yr) 32.4±4.42 29.7±3.56 0.347 0.150 Height (cm) 166.7±7.55 166.9±6.57 0.441 0.950 Weight (kg) 59.2±12.38 60.5±11.60 0.423 0.811 CVA 45.78±1.05 54.09±1.05 2.891 0.000 * FHP: forward head posture, NHP: normal head posture, CVA: craniovertebral angle. Mean±SD; * p<0.05. Figure 1. Craniovertebral angle. 2 www.kptjournal.org
Muscle Activity during Cranio-Cervical Flexion Exercise 을부착하여촬영하였고, 촬영후이미지에서대상자의귀구슬과일곱번째목뼈의가시돌기를연결한선과수평선이이루는각도를 NIH image J ver 1.47 (Sun Microsystems Inc., USA) 의프로그램을이용하여각도를계산하였다 (Figure 1). Nemmers 등 15 의연구에의하면 45 세이하의성인의정상적인머리-척추각은 49 에서 59 의범위를가진다고보고하였다. 이에따라본연구는머리-척추각에따라앞쪽머리자세의앞쪽머리자세군은 49 미만, 정상자세의정상자세군은 49 에서 59 사이의범위로나누어각군당 10명씩배정하였다. 2) 머리- 목굽힘운동머리-목굽힘운동은올바른목뼈정렬을위한목의안정화운동으로환자또는건강한사람을대상으로임상에서많이사용되는운동방법이다. 11 또한, Hudswell 등 16 은머리-목굽힘운동은깊은목굽힘근의활성정도를측정하는데높은신뢰도를나타낸다고보고하였다. 대상자는바르게누워엉덩관절 60 굽힘과무릎관절 90 굽힘을유지한자세에서압력바이오피드백기구를뒤통수뼈아래, 위쪽목뼈부위에위치하여머리 -목굽힘운동을시행하였다. 머리 -목굽힘운동시, 압력바이오피드백기구의압력표시계는대상자의눈에서정면으로위치하였고, 정확한측정을위하여대상자팔의사용을억제하기위해고정하여설치하였다. 휴지기인 20 mmhg에서 22, 24, 26, 28, 30 mmhg까지 2 mmhg의압력을증가시켜총 6단계의압력에서시행하였으며, 17 압력마다 10초간유지한후 2분간휴식을취하였다. 3) 근전도측정근전도신호의표본추출률 (sampling rate) 은 1,000 Hz로설정하고, 주파수대역폭 (bandpass) 은 20-450 Hz를사용하였으며, 근전도신호는제곱평균제곱근법 (root mean square, RMS) 으로처리하여분석하였다. 전극은전극간의거리를 2 cm로유지하여근섬유방향에평행하게부착하였으며, 부착전근전도신호에대한피부저항을감소시키기위해부착부위를가는사포로 3-4회문질러피부각질층을제거하고, 소독용알코올로닦아내었다. 전극은우측목빗근과앞목갈비근에부착하였으며, 목빗근은꼭지돌기와빗장뼈의중간지점, 앞목갈비근은목빗근으로부터가쪽으로이동하여빗장뼈와위등세모근윗부분이이루는삼각형지점에부착하였다. 18 얕은목굽힘근의활성도를정규화 (normalization) 하기위해, 최대등척성수의적수축 (maximal voluntary isometric contraction, MVIC) 시근활성도를측정하여제곱평균제곱근법으로처리된각근육의활성도를백분율 (%MVIC) 로분석하였다. 최대등척성수의적수축정도의측정을위해대상자는머리-목굽힘운동시행자세를취하고목을앞쪽굽힘시, 검사자는대상자이마에저항을제공한다. 최대등척성수의적수축정도의측정은 7초간 3회측정하는데, 처음과마 Figure 2. Ultrasonographic of SCM, CA, LC. SCM: sternocleidomastoid muscle, CA: carotid artery, LC: Longus colli muscle. 지막 1 초를제외한값의 3 회평균값을사용하였다. 4) 초음파촬영및측정 머리 - 목굽힘운동시초음파의탐촉자 (probe) 를대상자의기관 (trachea) 에서오른쪽으로 5 cm 떨어진부위에세로방향으로평행하게 위치하였다. 초음파장비의화면을통해나오는영상에서목빗근, 목 동맥, 고리판 (laminae) 의영상이잘보이도록위치를조절하였으며, 19 세번반복측정하여촬영영상이가장깨끗한이미지를선택하여의 료영상저장전송시스템 (picture archiving and communication system, PACS) 을이용하여결과값을측정하였다. 측정방법은이미지중앙에기준선을그어중앙선으로부터각각 1 cm, 2 cm, 3 cm 간격으로수직선을그어세개의수직선에위치된목 긴근의두께를측정하는데, 목동맥과목긴근위쪽근막경계부에서 부터, 아래쪽고리판의경계부사이의거리를측정하였다. 세개의수 직선에측정된선의길이를평균값으로산출하였다 (Figure 2). 19 4. 분석방법 머리, 목굽힘운동시발생된압력에따라정상자세군과앞쪽머리 자세군의목긴근두께변화, 목빗근과앞목갈비근활성도를비교하 기위해반복측정분산분석 (repeated measures ANOVA) 을실시하였 으며, 유의수준은 α = 0.05 로하였다. 사후검정은본페로니교정 (Bonferroni correction) 을시행하였으며유의수준 α= 0.01 로하였다. 앞쪽머리자세군과정상자세군간의차이를알아보기위하여독 립표본 t- 검정 (independent t-test) 을실시하였다. 통계처리는 SPSS for Windows (Ver. 22.0) 를사용하였다. www.kptjournal.org 3
The Journal of Korean Physical Therapy Donghoon Kang, et al. Table 2. Comparison of DCF thickness according pressure level between FHP group and NHP group (unit: cm) 20 mmhg 22 mmhg 24 mmhg 26 mmhg 28 mmhg 30 mmhg F p LC FHP 0.71±0.05 0.72±0.05 0.71±0.05 0.72±0.06 0.72±0.05 0.72± 0.06 163.788.000 * NHP 0.69±0.03 0.71±0.03 0.73±0.03 0.77± 0.04 0.80±0.04 0.84±0.04 t 5.435 2.550 3.372 2.198 1.110 2.469 p 0.470 0.578 0.359 0.026* 0.003 * 0.000 * LC: longus colli muscle, FHP: forward head posture, NHP: normal head posture. Mean±SD; * p<0.05. Table 3. Comparison of SCM and AS activity according pressure level between FHP group and NHP group (unit: %) 20 mmhg 22 mmhg 24 mmhg 26 mmhg 28 mmhg 30 mmhg F p SCM (%MVIC) FHP 12.91±2.25 13.19±2.43 13.50± 2.41 14.08± 2.79 15.14± 3.10 16.64± 3.10 39.968.000 * NHP 12.98±1.50 13.33±1.67 13.53± 1.57 13.63± 1.70 13.84± 1.76 14.18± 1.72 t 3.206 2.754 3.430 3.663 3.565 4.956 p 0.939 0.880 0.976 0.670 0.266 0.046 * AS (%MVIC) FHP 13.74±2.40 14.04±2.20 14.09± 2.51 14.96± 2.67 15.51± 2.95 17.11± 2.93 4.283.000 * NHP 13.38±1.28 13.58±1.38 13.53± 1.45 13.71± 1.52 13.97± 1.67 14.09± 1.79 t 7.482 4.536 6.680 3.245 4.295 4.816 p 0.681 0.584 0.549 0.215 0.170 0.014 * SCM: sternocleidomastoid, AS: anterior scalene, FHP: forward head posture, NHP: normal head posture. Mean±SD; * p<0.05. 결과 1. 연구대상자의특성본연구대상자의특성은 Table 1과같으며, 앞쪽머리자세군과정상자세군의사전동질성을분석한결과군간유의한차이는없는것으로나타났다. 앞쪽머리자세군과정상자세군간의머리-척추각의차이를비교분석한결과군간유의한차이를보였다. 2. 압력에따른깊은목굽힘근두께분석앞쪽머리자세군내압력별근두께차이는휴지기 20 mmhg와비교했을때, 28, 30 mmhg에서통계학적인유의한증가를나타냈다 (p < 0.05). 정상자세군은모든압력에따라통계학적으로유의한증가를나타냈다 (p < 0.05)(Table 2). 압력별로앞쪽머리자세군과정상자세군간의비교에서 26 mmhg 부터 30 mmhg에서는통계학적으로유의한차이가있었다 (p < 0.05). 3. 압력에따른목빗근활성도분석앞쪽머리자세군은 24 mmhg에서 30 mmhg까지압력에서유의한증가를나타냈고, 정상자세군은 26 mmhg에서 30 mmhg까지압력에서유의한증가를나타냈다 (p< 0.05)(Table 3). 압력별로앞쪽머리자세군과정상자세군간비교분석결과 30 mmhg에서는통계학적으로유의한차이가있었다 (p< 0.05). 4. 압력에따른앞목갈비근활성도분석앞쪽머리자세군은 26 mmhg에서 30 mmhg까지의압력에서유의한증가를나타냈지만 (p < 0.05), 정상자세군은모든압력에서유의한차이가없었다 (p< 0.05)(Table 3). 압력별로앞쪽머리자세군과정상자세군간비교분석결과 30 mmhg 의압력에서는통계학적으로유의한차이가있었다 (p < 0.05). 고찰본연구는머리-목굽힘운동시발생된압력에따라정상자세를가진성인과앞쪽머리자세를지닌성인의근활성도차이를비교하여머리-목굽힘운동방법의올바르고효과적인방법을제시하기위하여실시하였다. 앞쪽머리자세의정도를측정하는다양한방법이있는데본연구에서는높은신뢰도와타당도를보고한머리-척추각을측정하여앞쪽머리자세군과정상자세군으로나누어연구를진행하였다. 머리-목굽힘운동시압력에따른깊은목굽힘근인목긴근의두께변화와얕은목근육인목빗근과앞목갈비근의활성도를군에따라비교하였다. 본연구의결과깊은목굽힘근두께변화는앞쪽머리자세군과정상자세군모두압력증가에따라유의한증가를나타냈다. 정상자세군은모든압력에서유의한증가를나타냈고, 앞쪽머리자세군에서는휴지기 20 mmhg와비교했을때, 28, 30 mmhg에서유의한증가를나타냈다. 앞쪽머리자세군과정상자세군간비교에서는 26, 28, 30 4 www.kptjournal.org
Muscle Activity during Cranio-Cervical Flexion Exercise mmhg에서유의한차이를나타냈다. Falla 등 9 의연구에서머리, 목굽힘운동시압력증가에따라깊은목굽힘근의활성도증가량은양의상관관계가있다는연구결과와일치하며, Jesus 등 19 의목통증이없는정상성인 10명을대상으로한연구에서머리, 목굽힘운동시압력이증가함에따라깊은목굽힘근의두께가증가한결과와도일치하였다. 이러한결과는깊은목굽힘근인목긴근은척추중심축앞쪽에서주행하여근활동이이루어지고, 목뼈의굽힘근으로작용하여머리-목굽힘운동시압력이증가할수록굽힘의범위가증가되므로더큰근활성을필요로인해나타난결과로사료된다. 앞쪽머리자세군에대해정상자세군이압력에따라활발한근활성도를나타내었는데, Ishida 등 20 의연구에서앞쪽머리자세를가진사람의목긴근의근두께가정상자세를가진사람에비해감소하여근활성도가낮아진다는결과와일치하였다. 머리-목굽힘운동시압력에따라목빗근의활성도를살펴보면, 앞쪽머리자세군과정상자세군모두압력증가에따라유의한증가를나타냈다. 앞쪽머리자세군은 26, 28, 30 mmhg에서유의한증가를나타냈고, 앞쪽머리자세군에서는 24, 26, 28, 30 mmhg에서유의한증가를나타냈다. 앞쪽머리자세군과정상자세군간차이에서는 30 mmhg에서유의한차이를보였다. 이는목통증이없는 21세에서부터 53세까지의정상성인 10명을대상으로한 Falla 등 21 의연구와목통증이없는정상성인 10명을대상으로한 Jesus 등 19 의연구에서머리-목굽힘운동시압력증가에따라목빗근활성의증가를나타난결과와일치하였다. 이는목의굽힘을담당하는목빗근은얕은층에서목뒤쪽의유돌기에정지하는근육으로머리, 목굽힘운동시위쪽목뼈에서굽힘이발생되어목빗근의활성도가증가한것으로사료된다. 압력에따른근활성도를살펴보게되면, Jesus 등 19 의목통증이없는정상성인 10명을대상으로한연구에서 26, 28, 30 mmhg 의단계에서유의한증가를나타낸결과와본연구의정상자세군에서의결과와일치함을확인할수있었다. 앞선연구들과유사하고일치된결과를보이는것은머리, 목굽힘압력이증가함에따라위쪽목뼈의굽힘증가로목빗근의활성이더욱요구되어근활성증가가나타난것으로사료된다. 머리, 목굽힘운동시 30 mmhg의압력에서앞쪽머리자세과정상자세군간유의한차이를보였는데, 이는머리, 목굽힘운동시앞쪽머리자세를지닌대상자가목빗근의과도한긴장으로목앞쪽에압박감을주어관절가동범위제한을유발하여머리-목굽힘검사의수행을어렵게하므로 9,22, 30 mmhg의높은압력에서는다른압력에비해높은근활성의필요로정상자세군에비해앞쪽머리자세군에서근활성도증가가나타난것으로사료된다. 머리-목굽힘운동시압력에따라앞목갈비근의활성도를살펴보게되면, 정상자세군은유의한증가가나타나지않음과달리, 앞쪽머리자세군은 26, 28, 30 mmhg에서유의한증가를나타냈다. 앞쪽머리 자세군과정상자세군간차이에서는 30 mmhg에서유의한차이를보였다. Johnston 등 23 의통증이없는정상군과통증이있는근로자군을대상으로머리, 목굽힘운동시근활성도를비교한연구에서근로자군의 22, 24, 26, 28, 30 mmhg의압력에서앞목갈비근활성도가유의한증가가나타난결과와유사한결과를보였다. 비록통증을호소하는근로자를대상으로한선행연구와달리, 본연구에서는앞쪽머리자세를지닌대상자를선정하여조건은일치하지않으나, 오랜기간컴퓨터를사용함에따라앞쪽머리자세를유발한다는여러선행연구들의결과에따라근로자의앞쪽머리자세군또한, 앞쪽머리자세가유발된것으로볼수있다. 따라서선행연구의근로자군과본연구의앞쪽머리자세군에서압력이증가함에따라앞목갈비근활성도가유사하게증가된것으로사료된다. 앞쪽머리자세군과정상자세군간차이에서목빗근과마찬가지로 30 mmhg의압력에서유의한차이를보였다. Falla 등 9 의연구에따르면, 앞쪽머리자세로인하여깊은목굽힘근의활동이감소하여 30 mmhg의높은압력에서앞목갈비근과같은얕은목굽힘근의활성도증가로머리, 목굽힘운동을수행하기위한목근육들의운동전략이재구성되어정상자세군에비해앞쪽머리자세군의앞목갈비근의활성도증가가크게나타난것으로사료된다. 본연구에서머리, 목굽힘운동시압력에따라정상자세군에서앞쪽머리자세군에비해깊은목굽힘근인목긴근두께의증가를보였고, 앞쪽머리자세군에서는정상자세군에비해얕은목굽힘근들의활성도증가를보였다. 이는여러선행연구들과일치된결과를나타냈다. 머리, 목굽힘운동시본연구의정상자세군에서깊은목굽힘근은모든압력에서유의한증가를나타냈고, 앞쪽머리자세군에서는 28, 30 mmhg의압력에서유의한증가를나타냈다. 앞쪽머리자세군과정상자세군간비교에서는 26, 28, 30 mmhg의압력에서유의한차이를나타냈다. 얕은목굽힘근들인목빗근과앞목갈비근의활성도에서는 30 mmhg의압력에서정상자세군과앞쪽머리자세군간유의한차이가나타났다. 이러한결과를종합했을때, 깊은목굽힘근의높은활성과얕은목굽힘근낮은활성을위해서는정상자세를지닌성인을대상으로는 26, 28, 30 mmhg의압력이, 앞쪽머리자세를지닌성인은 28 mmhg 의압력이적절하다고사료된다. 본연구의제한점으로첫째, 연구대상자가충분한숫자에미치지못하며둘째, 깊은목근육과얕은목근육의활성도를측정하기에동시적인검사가이루어지지못했다는점이다. 초음파영상으로깊은목근육과얕은목근육중목빗근의활성도측정은동시에가능하지만, 앞목갈비근활성도를측정하는데에는제한이있어, 앞목갈비근의활성도를확인하기위해초음파와근전도, 두차례의실험을각각진행하였다는점이다. 향후본연구에서나타난제한점을보완할수 www.kptjournal.org 5
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