Original Article

The Acupuncture 2014; 31(2): 99-109

Published online June 20, 2014

https://doi.org/10.13045/acupunct.2014028

© Korean Acupuncture & Moxibustion Medicine Society

대학생의 스마트폰 이용 시간과 경항통과의 관련성 연구

이지인, 송호섭*

가천대학교 한의과대학 침구의학교실

Received: May 15, 2014; Revised: May 15, 2014; Accepted: May 24, 2014

The Correlation Analysis between Hours of Smartphone Use And Neck Pain in the Gachon University Students

Ji In Lee and Ho Sueb Song*

Department of Acupuncture & Moxibustion Medicine, College of Orinetal Medicine, Gachon University

Correspondence to : *Department of Acupuncture & Moxibustion Medicine, Gil Oriental Medicine Hospital of Gachon Univercity, 12, Dokjeom-ro 29beon-gil, Namdong-gu, Incheon, 405-760, Republic of Korea
Tel : +82-70-7120-5012 Email : hssong70@gachon.ac.kr

Received: May 15, 2014; Revised: May 15, 2014; Accepted: May 24, 2014

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Objectives : The purpose of this study was to analysis the relationship between hours of smartphone use and neck pain in university students.
Methods : A survey of 2,353 university students was conducted in Gyeonggi province and Incheon city using a self report questionnaire from April 1 to 11 2013. The questionnaire of questions regarding the hours of using smartphone, mainly used function in participant’s smartphone and neck discomfort degree. Neck disability index(NDI) was used to evaluate degree of pain. The collected data were analyzed with the t-test and Kendall's tau test using the SPSS 21.0 program and R 3.1.0, respectively.
Results : 1. Almost all of the survey participants(99.07 %) were smartphone users. 66.97 % of them answered that they use their smartphone daily more than 2 hours and 48.18 % of them answered that they use their smartphone 10 to 30 minutes everytime they use it.
2. The overall distribution of NDI scores was ‘no disability(0~4 score, 62.92 %)’, ‘mild disability(5~14 score, 32.85 %)’, ‘moderate disability(15~24 score, 1.19 %)’. As a result of t-test, we found that the average NDI score for female students was significantly higher than the average NDI score for male students(p<0.05).
3. The Kendall’s tau test revealed that total time spent daily using smartphones has a strong positive correlation with ‘pain intensity’, ‘lifting’, ‘reading’ ‘headache’, ‘concentration’, and ‘driving’(p<0.05) in NDI. Also, time duration of one time smartphone usage has a strong positive correlation with ‘pain intensity’, ‘lifting’, ‘reading’, ‘headache’, ‘concentration’, ‘work’, and ‘recreation’(p<0.05).
4. The Kendall’s tau test revealed that total NDI scores have a significantly strong positive correlation with both of total time spent daily using smartphones(p<0.05) and time duration for one time smartphone usage(p<0.05). This results imply that long-time use of smartphone has a strong relationship with neck pain.
Conclusions : The results of the study would be a good starting point for future studies to reduce the risks of chronic neck pain caused by smartphone usage.

Keywords Smartphone; NDI; Headache; Neck pain

General Characteristics of Participants

CheracteristicsCategoriesN(%) or M±SD
GenderMale836(35.53)
Female1,517(64.47)

MajorMedicine377(16.02)
Architecture151(6.42)
Arts212(9.01)
Liberal arts150(6.37)
Business department428(18.19)
Engineering475(20.19)
Social study250(10.62)
Physical department38(1.62)
Education
31(1.32)
Nature science241(10.24)

Total2,353(100)

Age(year)23.15±4.47

Displays the number of participanis with percent(%).


Participant’s Major Using Function in Smartphone

CategoriesMaleFemaleTotal
Messanger, text massage523(62.56)965(63.61)1,488(63.84)
Games54(6.46)65(4.28)119(5.11)
Web surfing213(25.48)418(27.55)631(27.07)
Phone call13(1.56)27(1.78)40(1.72)
Other27(3.23)26(1.71)53(2.27)

Subtotal830(100.00)1,501(100.00)2,331(100.00)
t= 0.70*, p value = 0.484**

Displays the number of participanis with percent(%).

*t score, p-value is calculated by Student’s t-test.

**p-value of Student’s t -test<0.05.


Smartphone Usage Hours of Participants

Total hours of use[per 1 day]The length of time for use[for 1 time]
Less than 30 minutes37(1.59)Less than 10 minutes749(32.13)
30 minutes ~ 1 hour205(8.79)10 ~ 30 minutes1,123(48.18)
1 ~ 2 hours528(22.65)30 ~ 1 hour354(15.19)
2 ~ 4 hours800(34.32)Over 1 hour105(4.51)
Over 4 hours761(32.65)

Total2,331(100)Total2,331(100)

Displays the number of participants with percent(%).


Participants Distribution in Each Subject of NDI

SubjectSexOption(score)Total

1(0)2(1)3(2)4(3)5(4)6(5)
Pain intensityM429 (51.32)258 (30.86)97 (11.60)36 (4.31)12 (1.44)4 (0.48)836 (100)
F714 (47.07)448 (29.53)222 (14.63)92 (6.06)26 (1.71)15 (0.99)1,517 (100)

Personal careM779 (93.18)51 (6.10)5 (0.60)1 (0.12)0 (0.00)0 (0.00)836 (100)
F1445 (95.25)61 (4.02)1 (0.07)5 (0.33)5 (0.33)0 (0.00)1,517 (100)

LiftingM731 (87.44)99 (11.84)4 (0.48)1 (0.12)1 (0.12)0 (0.00)836 (100)
F1251 (82.47)251 (16.55)9 (0.59)4 (0.26)1 (0.07)1 (0.07)1,517 (100)

ReadingM467 (55.86)307 (36.72)48 (5.74)13 (1.56)1 (0.12)0 (0.00)836 (100)
F725 (47.79)649 (42.78)98 (6.46)37 (2.44)8 (0.53)0 (0.00)1,517 (100)

HeadacheM445 (53.23)335 (40.07)44 (2.90)8 (0.96)2 (0.24)2 (0.24)836 (100)
F433 (28.54)871 (57.42)147 (9.69)45 (2.97)18 (1.19)3 (0.20)1,517 (100)

ConcentrationM277 (33.13)405 (48.44)128 (15.31)19 (2.27)5 (0.60)2 (0.24)836 (100)
F488 (32.17)685 (45.15)293 (19.31)35 (2.31)15 (0.99)1 (0.07)1,517 (100)

WorkM691 (82.66)131 (15.67)14 (1.67)0 (0.00)0 (0.00)0 (0.00)836 (100)
F1085 (71.52)357 (23.53)72 (4.75)2 (0.13)1 (0.07)0 (0.00)1,517 (100)

DrivingM522 (84.88)83 (13.50)8 (1.30)1 (0.16)1 (0.16)0 (0.00)615* (73.56)
F447 (83.09)75 (13.94)8 (1.49)0 (0.00)1 (0.19)7 (1.30)538* (35.46)

SleepingM788 (94.26)44 (5.26)3 (0.36)0 (0.00)1 (0.12)0 (0.00)836 (100)
F1399 (92.22)112 (7.38)4 (0.26)1 (0.07)0 (0.00)1 (0.07)1,517 (100)

RecreationM728 (87.08)100 (11.96)4 (0.48)3 (0.36)1 (0.12)0 (0.00)836 (100)
F1326 (87.41)173 (11.40)11 (0.73)4 (0.26)3 (0.20)0 (0.00)1,517 (100)

Displays the number of participanis with percent(%).

*some of the participants don’t have driver’s license(male : 221, female : 979).


Participants Distribution in Total Score of NDI

No disability (0~4)Mild disability (5~14)Moderate disability (15~24)Severe disability (25~34)Complete disability (35~50)TotalM±SDt-score
M602 (72.01)227 (27.15)7 (0.84)0 (0.00)0 (0.00)836 (100)3.47 ±3.03−6.081*p** : 0.000
F949 (62.56)546 (35.99)21 (1.38)1 (0.06)0 (0.00)1,517 (100)4.31 ±3.28

Total1,551 (62.92)773 (32.85)28 (1.19)1 (0.04)0 (0.00)2,353 (100)4.01 ±3.22

Displays the number of participanis with percent(%).

*t score, p-value is calculated by Student’s t-test.

**p-value of Student’s t-test<0.05.


The correlation between total time spent daily using smartphones and NDI score

Subjectτ2-sided p value
Pain intensity0.072*0.0000**
Personal care−0.010*0.5948**
Lifting0.041*0.0299**
Reading0.061*0.0010**
Headache0.090*0.0000**
Concentration0.101*0.0000**
Work0.030*0.0919**
Driving0.045*0.0051**
Sleeping0.028*0.1449**
Recreation0.022*0.2560**
Total NDI score0.339*0.0000**

NDI : neck disability index.

*τ, p-value is calculated by Kendall’s tau test.

**p-value of Kendall’s tau <0.05.


The correlation between duration of 1 time smartphone usage and NDI score

Subjectτ2-sided p value
Pain intensity0.056*0.0022**
Personal care0.019*0.3397**
Lifting0.079*0.0001**
Reading0.058*0.0020**
Headache0.072*0.0001**
Concentration0.105*0.0000**
Work0.090*0.0000**
Driving0.007*0.7988**
Sleeping0.013*0.5126**
Recreation0.038*0.0498**
Total0.359*0.0000**

*τ, p-value is calculated by Kendall’s tau test.

**p-value of Kendall’s tau<0.05.


  1. Ministry of Science, ICT and Future Planning (MSIF). Statistics of Wireless Communication User 2014 [Internet] available from : http://www.msip.go.kr/www/brd/m_220/view.do?seq=428&srchFr=&srchTo=&srchWord=&srchTp=&multi_itm_seq=0&itm_seq_1=0&itm_seq_2=0&company_cd=&company_nm=&page=1.
  2. Lee, CS. A study on the consumer type for smart phone users to basis of motivations[dissertation]. Incheon: Incheon Univ; 2012. p. Korean.
  3. Lee, SH. Evaluating the influence of smart phone use on the psycho-physiological condition [dissertation]. Seoul: Konkook Univ; 2011. p. Korean.
  4. Park, JS, Choi, MJ, Ma, JE, Moon, JH, and Moon, HJ. Influence of cellular phone cideos and games on dry eye syndrome in university students. J Korean Acad Community Health Nurs 2014;25:12-23.
  5. Eom, SH, Choi, SY, and Park, DH. An empirical study on relationship between symptoms of musculoskeletal disorders and amount of smartphone usage. J of the Korea safety management & science 2013;15:113-20.
  6. Szeto, GP, and Lee, R. An ergonomic evaluation comparing desktop, notebook, and subnotebook computers. Archives of Physical Medicine and Rehabilitation 2002;83:527-32.
  7. Kim, DS, and Chae, WS. Biomechanical analysis of a smartphone task with different postures. Korean J of Sport Biomechanics 2012;22:253-9.
  8. Gak, HB. Analysis of the change of the neck pressure pain threshold in long term computer users. J of The Korea Contents Society 2008;8:151-8.
  9. Kim, YG, Kang, MY, Kim, JW, Jang, JH, and Oh, JS. Influence of the duration of smartphone usage on flexion angles of the cervical and lumbar spine and on reposition error in the cervical spine. Phys Ther Kor 2013;20:10-7.
  10. Lee, BI, Kim, SW, and Kim, YJ. The Relationship between smartphone usage time and physical and mental health of university students. J Korean Soc School Health 2013;26:45-53.
  11. Vernon, H, and Mior, S. The neck disability index: a study of reliability and validity. J Manipulative Physiol Ther 1991;14:409-15.
  12. Song, KJ, Choi, BW, Kim, SJ, and Yoon, SJ. Crosscultural adaptation and validation of the Korean version of the neck disability index. J Korean Orthop Assoc 2009;44:350-9.
  13. Moon, JD, Lee, MC, and Kim, BW. A study on the factors afecting the subjective symptoms of VDT syndrome. Korean J Prev Med 1991;24:373-89.
  14. Oh, HJ, Kwon, WA, Kim, DD, Lee, JH, Um, KM, and Song, YH. The prevalence of neck disability index among some college students. J of the Korea Academia-Industrial Cooperation Society 2010;11:4812-8.
  15. Wijnhoven, HA, de Vet, HC, and Picavet, HS. Prevalence of musculoskeletal disorders is systematically higher in women than in men. Clin J Pain 2006;22:717-24.
  16. Leboeuf-Yde, C, Nielsen, J, Kyvik, KO, Fejer, R, and Hartvigsen, J. Pain in the lumbar, thoracic or cervical regions: do age and gender matter? a population-based study of 34,902 Danish twins 20–71 years of age. BMC Musculoskelet Disord 2009;10:39.
  17. Son, KM, Cho, NH, Lim, SH, and Kim, HA. Prevalence and risk factor of neck pain in elderly Korean community residents. J Korean Med Sci 2013;28:680-6.
  18. Gwendolen, Jull, Sterling, Michele, Falla, Deborah, Treleaven, Julia, and Leary, Shaun O. Whiplash, headache, and neck pain. Seoul: Koonja Publishing Company; 2011. p. 1-69.
  19. Szeto, GP, and Lee, R. An ergonomic evaluation comparing desktop, notebook, and subnotebook computers. Arch Phys Med Rehabil 2002;83:527-32.
  20. Florence, PK, Elizabeth, KM, Patricia, GP, Mary, MR, and William, AR. Muscles: testing and function with posture and pain 5/E. Seoul: Hanmibook; 2006. p. 152-61.
  21. Fernández-de-las-Peñas, C, Cuadrado, ML, and Pareja, JA. Myofascial trigger points, neck mobility, and forward head posture in episodic tension-type headache. The J of Head and Face Pain 2007;47:662-72.
  22. Chae, YW. The effect of forward head posture and cervical ROM on chronic and episodic tension-type. Headache in university students 2009;21:71-7.
  23. Fejer, R, Kyvik, KO, and Hartvigsen, J. The prevalance of neck pain in the world population: a systematic critical review of the literature. Eur Spine J 2006;15:834-48.

Article

Original Article

The Acupuncture 2014; 31(2): 99-109

Published online June 20, 2014 https://doi.org/10.13045/acupunct.2014028

Copyright © Korean Acupuncture & Moxibustion Medicine Society.

대학생의 스마트폰 이용 시간과 경항통과의 관련성 연구

이지인, 송호섭*

가천대학교 한의과대학 침구의학교실

Received: May 15, 2014; Revised: May 15, 2014; Accepted: May 24, 2014

The Correlation Analysis between Hours of Smartphone Use And Neck Pain in the Gachon University Students

Ji In Lee and Ho Sueb Song*

Department of Acupuncture & Moxibustion Medicine, College of Orinetal Medicine, Gachon University

Correspondence to:*Department of Acupuncture & Moxibustion Medicine, Gil Oriental Medicine Hospital of Gachon Univercity, 12, Dokjeom-ro 29beon-gil, Namdong-gu, Incheon, 405-760, Republic of Korea
Tel : +82-70-7120-5012 Email : hssong70@gachon.ac.kr

Received: May 15, 2014; Revised: May 15, 2014; Accepted: May 24, 2014

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Objectives : The purpose of this study was to analysis the relationship between hours of smartphone use and neck pain in university students.
Methods : A survey of 2,353 university students was conducted in Gyeonggi province and Incheon city using a self report questionnaire from April 1 to 11 2013. The questionnaire of questions regarding the hours of using smartphone, mainly used function in participant’s smartphone and neck discomfort degree. Neck disability index(NDI) was used to evaluate degree of pain. The collected data were analyzed with the t-test and Kendall's tau test using the SPSS 21.0 program and R 3.1.0, respectively.
Results : 1. Almost all of the survey participants(99.07 %) were smartphone users. 66.97 % of them answered that they use their smartphone daily more than 2 hours and 48.18 % of them answered that they use their smartphone 10 to 30 minutes everytime they use it.
2. The overall distribution of NDI scores was ‘no disability(0~4 score, 62.92 %)’, ‘mild disability(5~14 score, 32.85 %)’, ‘moderate disability(15~24 score, 1.19 %)’. As a result of t-test, we found that the average NDI score for female students was significantly higher than the average NDI score for male students(p<0.05).
3. The Kendall’s tau test revealed that total time spent daily using smartphones has a strong positive correlation with ‘pain intensity’, ‘lifting’, ‘reading’ ‘headache’, ‘concentration’, and ‘driving’(p<0.05) in NDI. Also, time duration of one time smartphone usage has a strong positive correlation with ‘pain intensity’, ‘lifting’, ‘reading’, ‘headache’, ‘concentration’, ‘work’, and ‘recreation’(p<0.05).
4. The Kendall’s tau test revealed that total NDI scores have a significantly strong positive correlation with both of total time spent daily using smartphones(p<0.05) and time duration for one time smartphone usage(p<0.05). This results imply that long-time use of smartphone has a strong relationship with neck pain.
Conclusions : The results of the study would be a good starting point for future studies to reduce the risks of chronic neck pain caused by smartphone usage.

Keywords: Smartphone, NDI, Headache, Neck pain

Table 1 .. General Characteristics of Participants.

CheracteristicsCategoriesN(%) or M±SD
GenderMale836(35.53)
Female1,517(64.47)

MajorMedicine377(16.02)
Architecture151(6.42)
Arts212(9.01)
Liberal arts150(6.37)
Business department428(18.19)
Engineering475(20.19)
Social study250(10.62)
Physical department38(1.62)
Education
31(1.32)
Nature science241(10.24)

Total2,353(100)

Age(year)23.15±4.47

Displays the number of participanis with percent(%)..


Table 2 .. Participant’s Major Using Function in Smartphone.

CategoriesMaleFemaleTotal
Messanger, text massage523(62.56)965(63.61)1,488(63.84)
Games54(6.46)65(4.28)119(5.11)
Web surfing213(25.48)418(27.55)631(27.07)
Phone call13(1.56)27(1.78)40(1.72)
Other27(3.23)26(1.71)53(2.27)

Subtotal830(100.00)1,501(100.00)2,331(100.00)
t= 0.70*, p value = 0.484**

Displays the number of participanis with percent(%)..

*t score, p-value is calculated by Student’s t-test.

**p-value of Student’s t -test<0.05.


Table 3 .. Smartphone Usage Hours of Participants.

Total hours of use[per 1 day]The length of time for use[for 1 time]
Less than 30 minutes37(1.59)Less than 10 minutes749(32.13)
30 minutes ~ 1 hour205(8.79)10 ~ 30 minutes1,123(48.18)
1 ~ 2 hours528(22.65)30 ~ 1 hour354(15.19)
2 ~ 4 hours800(34.32)Over 1 hour105(4.51)
Over 4 hours761(32.65)

Total2,331(100)Total2,331(100)

Displays the number of participants with percent(%)..


Table 4 .. Participants Distribution in Each Subject of NDI.

SubjectSexOption(score)Total

1(0)2(1)3(2)4(3)5(4)6(5)
Pain intensityM429 (51.32)258 (30.86)97 (11.60)36 (4.31)12 (1.44)4 (0.48)836 (100)
F714 (47.07)448 (29.53)222 (14.63)92 (6.06)26 (1.71)15 (0.99)1,517 (100)

Personal careM779 (93.18)51 (6.10)5 (0.60)1 (0.12)0 (0.00)0 (0.00)836 (100)
F1445 (95.25)61 (4.02)1 (0.07)5 (0.33)5 (0.33)0 (0.00)1,517 (100)

LiftingM731 (87.44)99 (11.84)4 (0.48)1 (0.12)1 (0.12)0 (0.00)836 (100)
F1251 (82.47)251 (16.55)9 (0.59)4 (0.26)1 (0.07)1 (0.07)1,517 (100)

ReadingM467 (55.86)307 (36.72)48 (5.74)13 (1.56)1 (0.12)0 (0.00)836 (100)
F725 (47.79)649 (42.78)98 (6.46)37 (2.44)8 (0.53)0 (0.00)1,517 (100)

HeadacheM445 (53.23)335 (40.07)44 (2.90)8 (0.96)2 (0.24)2 (0.24)836 (100)
F433 (28.54)871 (57.42)147 (9.69)45 (2.97)18 (1.19)3 (0.20)1,517 (100)

ConcentrationM277 (33.13)405 (48.44)128 (15.31)19 (2.27)5 (0.60)2 (0.24)836 (100)
F488 (32.17)685 (45.15)293 (19.31)35 (2.31)15 (0.99)1 (0.07)1,517 (100)

WorkM691 (82.66)131 (15.67)14 (1.67)0 (0.00)0 (0.00)0 (0.00)836 (100)
F1085 (71.52)357 (23.53)72 (4.75)2 (0.13)1 (0.07)0 (0.00)1,517 (100)

DrivingM522 (84.88)83 (13.50)8 (1.30)1 (0.16)1 (0.16)0 (0.00)615* (73.56)
F447 (83.09)75 (13.94)8 (1.49)0 (0.00)1 (0.19)7 (1.30)538* (35.46)

SleepingM788 (94.26)44 (5.26)3 (0.36)0 (0.00)1 (0.12)0 (0.00)836 (100)
F1399 (92.22)112 (7.38)4 (0.26)1 (0.07)0 (0.00)1 (0.07)1,517 (100)

RecreationM728 (87.08)100 (11.96)4 (0.48)3 (0.36)1 (0.12)0 (0.00)836 (100)
F1326 (87.41)173 (11.40)11 (0.73)4 (0.26)3 (0.20)0 (0.00)1,517 (100)

Displays the number of participanis with percent(%)..

*some of the participants don’t have driver’s license(male : 221, female : 979).


Table 5 .. Participants Distribution in Total Score of NDI.

No disability (0~4)Mild disability (5~14)Moderate disability (15~24)Severe disability (25~34)Complete disability (35~50)TotalM±SDt-score
M602 (72.01)227 (27.15)7 (0.84)0 (0.00)0 (0.00)836 (100)3.47 ±3.03−6.081*p** : 0.000
F949 (62.56)546 (35.99)21 (1.38)1 (0.06)0 (0.00)1,517 (100)4.31 ±3.28

Total1,551 (62.92)773 (32.85)28 (1.19)1 (0.04)0 (0.00)2,353 (100)4.01 ±3.22

Displays the number of participanis with percent(%)..

*t score, p-value is calculated by Student’s t-test.

**p-value of Student’s t-test<0.05.


Table 6 .. The correlation between total time spent daily using smartphones and NDI score.

Subjectτ2-sided p value
Pain intensity0.072*0.0000**
Personal care−0.010*0.5948**
Lifting0.041*0.0299**
Reading0.061*0.0010**
Headache0.090*0.0000**
Concentration0.101*0.0000**
Work0.030*0.0919**
Driving0.045*0.0051**
Sleeping0.028*0.1449**
Recreation0.022*0.2560**
Total NDI score0.339*0.0000**

NDI : neck disability index..

*τ, p-value is calculated by Kendall’s tau test.

**p-value of Kendall’s tau <0.05.


Table 7 .. The correlation between duration of 1 time smartphone usage and NDI score.

Subjectτ2-sided p value
Pain intensity0.056*0.0022**
Personal care0.019*0.3397**
Lifting0.079*0.0001**
Reading0.058*0.0020**
Headache0.072*0.0001**
Concentration0.105*0.0000**
Work0.090*0.0000**
Driving0.007*0.7988**
Sleeping0.013*0.5126**
Recreation0.038*0.0498**
Total0.359*0.0000**

*τ, p-value is calculated by Kendall’s tau test.

**p-value of Kendall’s tau<0.05.


References

  1. Ministry of Science, ICT and Future Planning (MSIF). Statistics of Wireless Communication User 2014 [Internet] available from : http://www.msip.go.kr/www/brd/m_220/view.do?seq=428&srchFr=&srchTo=&srchWord=&srchTp=&multi_itm_seq=0&itm_seq_1=0&itm_seq_2=0&company_cd=&company_nm=&page=1.
  2. Lee, CS. A study on the consumer type for smart phone users to basis of motivations[dissertation]. Incheon: Incheon Univ; 2012. p. Korean.
  3. Lee, SH. Evaluating the influence of smart phone use on the psycho-physiological condition [dissertation]. Seoul: Konkook Univ; 2011. p. Korean.
  4. Park, JS, Choi, MJ, Ma, JE, Moon, JH, and Moon, HJ. Influence of cellular phone cideos and games on dry eye syndrome in university students. J Korean Acad Community Health Nurs 2014;25:12-23.
  5. Eom, SH, Choi, SY, and Park, DH. An empirical study on relationship between symptoms of musculoskeletal disorders and amount of smartphone usage. J of the Korea safety management & science 2013;15:113-20.
  6. Szeto, GP, and Lee, R. An ergonomic evaluation comparing desktop, notebook, and subnotebook computers. Archives of Physical Medicine and Rehabilitation 2002;83:527-32.
  7. Kim, DS, and Chae, WS. Biomechanical analysis of a smartphone task with different postures. Korean J of Sport Biomechanics 2012;22:253-9.
  8. Gak, HB. Analysis of the change of the neck pressure pain threshold in long term computer users. J of The Korea Contents Society 2008;8:151-8.
  9. Kim, YG, Kang, MY, Kim, JW, Jang, JH, and Oh, JS. Influence of the duration of smartphone usage on flexion angles of the cervical and lumbar spine and on reposition error in the cervical spine. Phys Ther Kor 2013;20:10-7.
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Jan 07, 2025 Volume 42:1~130

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