Reliability evaluation of head position assessment methods

Gwanseob Shin,Chang-hyung Lee,Sojung Lee,Hwayeong Kang 대한인간공학회 2014 대한인간공학회 학술대회논문집 Vol.2014 No.5

Reliable assessment of forward head posture (FHP) has been an important issue for the efficient rehabilitation of head/neck disorders and pain symptoms, but no standardized evaluation methods have yet been developed. The purpose of this study was to determine a reliable head position assessment method by evaluating the test-retest reliability of various static and dynamic head position variables and assessment conditions. Twenty healthy subjects were recruited and their head position relative to the upper back were measured by three different dimensions (horizontal gap between the tragus and the 7th cervical vertebra, horizontal gap between the tragus and the acromion processes, angle between vertical and a line of tragus-7th cervical vertebra) three times per dimension in 5 different posture conditions. Study results show that the head position variables varied significantly between posture conditions, indicating the importance of a standardized test method. Test-retest reliability evaluation results show that the tragus-C7 horizontal gap dimension was more reliable than other head position variables specifically when it was measured while standing or walking. Based on the findings of this study, it can be concluded that the severity of FHP can be more reliably assessed if the position of the head is measured when the patient is in standing or comfortable walking.

Reliability Evaluation of Head Position Assessment Methods

( Gwanseob Shin ),( Chang Hyung Lee ),( Sojung Lee ),( Hwayeong Kang ) 한국감성과학회 2014 춘계학술대회 Vol.2014 No.-

Reliable assessment of forward head posture (FHP) has been an important issue for the efficient rehabilitation of head/neck disorders and pain symptoms, but no standardized evaluation methods have yet been developed. The purpose of this study was to determine a reliable head position assessment method by evaluating the test-retest reliability of various static and dynamic head position variables and assessment conditions. Twenty healthy subjects were recruited and their head position relative to the upper back were measured by three different dimensions (horizontal gap between the tragus and the 7th cervical vertebra, horizontal gap between the tragus and the acromion processes, angle between vertical and a line of tragus-7th cervical vertebra) three times per dimension in 5 different posture conditions. Study results show that the head position variables varied significantly between posture conditions, indicating the importance of a standardized test method. Test-retest reliability evaluation results show that the tragus-C7 horizontal gap dimension was more reliable than other head position variables specifically when it was measured while standing or walking. Based on the findings of this study, it can be concluded that the severity of FHP can be more reliably assessed if the position of the head is measured when the patient is in standing or comfortable walking.

디스플레이 크기에 따른 사용자 선호 위치의 변화

신관섭(Gwanseob Shin),Sudeep Hegde 대한인간공학회 2010 대한인간공학회 학술대회논문집 Vol.2010 No.5

User-preferred position data of the computer display were quantified to determine how the size and/or the number of computer displays (19”, 24”, 27.5”, and dual 19” LCDs) influence the voluntary positioning of the computer display. Nineteen subjects performed a data entry task for 20 minutes with each of four display setups while their preferred display position data were periodically quantified. Subjects placed displays significantly (p<0.05) further as the size of display increased while maintaining the viewing angle of the top and center of display at or near eye height. Visual acuity reserve of all subjects (visual acuity of 20/30 or better) ranged from 2.0:1 to 3.2:1. No difference in viewing distance was found between the single 19” and the dual 19” setups. Results of this study suggest that users determine their preferred display position by the vertical dimension of display’s viewable area, while maintaining a viewing distance of at least twice larger than individual’s acuity threshold.

Use of antagonist muscle EMG in the assessment of neuromuscular health of the low back

Nakyung Lee,Gwanseob Shin,Hwayeong Kang 대한인간공학회 2014 대한인간공학회 학술대회논문집 Vol.2014 No.5

Surface electromyography (SEMG) has been frequently used in ergonomics and kinesiology research to assess the amount of physical efforts of skeletal muscles and resultant biomechanical stresses on body joints. The use of surface EMG as a diagnostic method in non-laboratory settings, however, has been limited due to its sensitivity to noises and difficulty in detecting signals from deep muscles. The objective of this study was to determine EMG variables and data collection methods that could identify changes in the spinal stability after pain-free 10-min static stooping. Twenty two subjects conducted simple physical tasks before and immediately after 10-min stooping, and their EMG variables were compared between pre- and post-stooping. In results, mean normalized amplitude of agonist muscles did not vary significantly after stooping, but the amplitude of antagonist muscles decreased after stooping. Decrements in the antagonist muscle activity were significant for flank and isometric back extension exercises (p<0.05). Findings of this study suggest the possibility of using surface EMG in the evaluation of spinal stability and low back health status in simple exercise postures. Changes in the amplitude of antagonist muscles may be indicative of changes in the spinal stability, and the sensitivity of the indicator can be improved, if measured in flank or back extension exercises where required moment to maintain a posture is primarily generated from the agonist muscles.

Hand usage pattern and upper body discomfort of desktop touchscreen users.

Kang, Hwayeong,Shin, Gwanseob Taylor Francis 2014 Ergonomics Vol.57 No.9

<P>A laboratory study was conducted to determine how users of different handedness interact with desktop touchscreen displays and how the hand usage pattern influences their body discomfort development. Twenty-one participants in three different handedness groups conducted simple web-browsing for 30 minutes using a 23 touchscreen display while their subjective body discomfort, frequency of use of each hand and touch area preference were periodically quantified. Participants reported a gradual increase in body discomfort during web-browsing, and the increments in body discomfort varied between handedness groups for some body parts. Results also show that right-handed participants had stronger laterality than the left-handed, and ambidextrous participants used both hands more evenly than other participants, suggesting associations between the hand usage pattern and body discomfort development. Findings of the current study suggest that body discomfort of desktop touchscreen display users could be moderated by user-interface improvements and user training.</P>

Relationship between subjective pain scale and muscle recruitment patterns of low back

Nakyung Lee,Gwanseob Shin 대한인간공학회 2014 대한인간공학회 학술대회논문집 Vol.2014 No.11

Objective: The main objective of this study was to investigate the relationship between self-reported back pain severity and muscle recruitment patterns while conducting common physical exercises. Background: Non-specific low back pain has been one of major concerns in various occupational environments. Reliable and quantitative assessment of the severity of non-specific low back pain is important in injury prevention as well as rehabilitation of injured individuals. While self-reported questionnaires such as the Oswestry Low Back Disability questionnaire have been frequently used to assess the severity of non-specific low back pain, no quantitative and objective assessment tool or system has yet been developed. Method: Twenty seven participants who had low back pain symptoms were grouped into three groups by their Oswestry disability score (less than 22; 23-30; greater than 30), and participated in a laboratory experiment. Myoelectric signals (EMG) of the lumbar erector spinae muscles and abdominal muscles were collected from each participant during common physical exercises, including walking, plank, bird-dog, and isometric back extension. Mean amplitude of each muscle, bilateral difference between left and right side muscles, and co-contraction ratio between abdominal and low back muscles were compared between the three Oswestry score groups. Results: Significant differences between score groups were observed only from the bird-dog exercise. Greater bilateral difference of the L2 lumbar erector spinae muscles and smaller bilateral difference of the recturs abdominal muscles were observed from groups with higher Oswestry scores. Conclusion: Severity of non-specific low back pain could be quantitatively assessed from the evaluation of muscle recruitment patterns in non-symmetric exercises such as bird-dog. Application: Results of this pioneering study could be used to develop reliable and easyto-use low back health monitoring systems.

Head flexion angle when web-browsing and texting using a smartphone while walking

Han, Hyeseon,Shin, Gwanseob Elsevier 2019 Applied ergonomics Vol.81 No.-

<P><B>Abstract</B></P> <P>The objective of this study was to quantify head flexion when using a smartphone while walking. Head flexion angle in the sagittal plane was measured from twenty-eight young users when conducting one-handed web-browsing while walking, two-handed texting while walking, and walking upright on a 60-m walkway. Participants walked with the head flexed 38.5° (median angle) during the two-handed texting and it was significantly greater (p < 0.05) than that of the one-handed web-browsing (31.1°) as well as of upright walking (−1.2°). The study results indicated that using a smartphone while walking would pose a larger load to the neck musculature compared to when walking without using a phone, and the load would be greater for two-handed texting than for one-handed browsing among the two smartphone tasks. The findings of this study can be used to inform smartphone users of potential risks of smartphone use while walking.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Median head flexion angle when using a smartphone while walking ranged 31.1°–38.5°. </LI> <LI> Participants flexed the head more when two-handed texting than one-handed browsing. </LI> <LI> They kept the head steadier when walking with texting than when just walking. </LI> </UL> </P>

Effects of the center of mass of a stick vacuum cleaner on the muscle activities of the upper extremity during floor vacuuming

Choi, Seobin,Shin, Gwanseob Elsevier Science B.V., Amsterdam. 2018 Applied ergonomics Vol.70 No.-

Effects of touch target location on performance and physical demands of computer touchscreen use

Kang, Hwayeong,Shin, Gwanseob Elsevier 2017 Applied ergonomics Vol.61 No.-

<P><B>Abstract</B></P> <P>Touchscreen interfaces for computers are known to cause greater physical stress compared to traditional computer interfaces. The objective of this study was to evaluate how physical demands and task performance of a tap gesture on a computer touchscreen vary between target locations and display positions. Twenty-three healthy participants conducted reach-tap-return trials with touch targets at fifteen locations in three display positions. Mean completion time, touch accuracy and electromyography of the shoulder and neck extensor muscles were compared between the target locations and display positions. The results demonstrated that participants completed the trial 12%–27% faster with 13%–39% less muscle activity when interacting with targets in the lower area of the display compared to when tapping upper targets (<I>p</I> < 0.05). The findings suggest that proper target placement and display positioning can improve task performance and lessen physical demands of computer touchscreen interface use.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Mean muscle activity of a tap gesture ranged from 4.5% to 14.2% max. </LI> <LI> Placing targets in the lower area of the display can lower muscle activity up to 39%. </LI> <LI> Users can complete a tap gesture up to 27% faster for targets in the lower area. </LI> <LI> Upright-closer display positioning is recommended to reduce physical demands. </LI> </UL> </P>

환자이송보조로봇 사용성 평가

Jeongmin Park,Gwanseob Shin 대한인간공학회 2016 대한인간공학회 학술대회논문집 Vol.2016 No.06