• Physical Therapy Korea
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• v.21 no.3
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• pp.28-37
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• 2014

The purpose of this study was to investigate the effects of smartphone use on muscle fatigue and tenderness in the cervical erector spinae (CES) and the upper trapezius (UT) and on the cervical range of motion among subjects with and without neck muscle pain. The subjects were 30 smartphone users in their 20 s who -were assigned to either an experimental group with neck muscle pain or a control group without neck muscle pain. Muscle fatigue and tenderness in the CES and the UT as well as the subjects' cervical range of motion were measured before and after 20-min smartphone sessions in a sitting position. In a between-group comparison of muscle fatigue, the experimental group showed a significantly greater decrease in median frequency in the CES and the right UT after smartphone use (p<.05). Regarding the assessment of muscle tenderness after smartphone use, the experimental group showed a statistically significant decrease in the pressure-pain threshold (PPT) in all muscles (p<.05), whereas the control group showed a significantly decreased PPT in the right CES and the UT (p<.05). The assessment of the cervical range of motion revealed a statistically significant reduction in the cervical flexion-extension and left lateral flexion in the experimental group (p<.05) after smartphone use. However, there was no significant change in the cervical range of motion in the control group (p>.05) after smartphone use. When compared with the control group, the experimental group demonstrated greater changes in cervical extension, lateral flexion, and rotation, except for cervical flexion (p<.05). In conclusion, when smartphone users have pre-existing neck muscle pain, the use of a smartphone further increased muscle fatigue and tenderness in the neck and reduced PPT and the cervical range of motion.

• Journal of the Korean Society of Physical Medicine
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• v.9 no.1
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• pp.125-132
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• 2014

PURPOSE: This study aims to determine the optimal knee joint angle and hip joint angle for minimizing the cervical muscle tension and maximizing the muscle activity of the trunk during the bridging exercise for trunk stabilization. METHODS: The bridging exercise in this study included seven forms of exercise: having a knee joint flexion angle of $120^{\circ}$, $90^{\circ}$, $60^{\circ}$, $45^{\circ}$ and hip joint abduction angle of $15^{\circ}$, $10^{\circ}$, $5^{\circ}$. The posture of the bridging exercise was as follows. To prevent the increase of hyper lumbar lordosis during the bridging exercise, the exercise was practiced after maintaining the lumbar neutral position through the pelvic posterior tilting exercise. RESULTS: The abduction angles did not result in statistically significant effects on the cervical erector, external oblique, rectus abdominis and erector spinae muscles. However, in relation to the knee joint angles, during the bridging exercise, statistically significant results were exhibited. CONCLUSION: The knee joint angle affected the muscle activity of the neck muscle. The greater the knee joint angle, the lower the load placed on the neck muscle. In contrast, the load increased as the knee joint angle decreased. In addition, the muscle activity of the neck muscle and trunk muscle increased as the knee joint angle decreased.

• Journal of Korean Medicine Rehabilitation
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• v.20 no.3
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• pp.37-60
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• 2010

Objectives : The purpose of this study was to investigate the relationship between masseter and cervical muscle activity and temporomandibular disorder in female office workers. Methods : Experimental group of 24 healthy subjects complained of temporomandibular joint related to computer use which lasted more than 3 months in the past year and was present in the past 7 days as well as on the day of test. Control group of 20 healthy subjects had no complaints of minimal discomfort on the day of test, and had no discomfort in the past 7 days. If they had reported discomfort in the past 12 months, it was of a short duration(<3 months) and resolved at least 3 months prior to participation. Outcomes were assessed by meridian-electromyography(MEMG), whole spin x-ray, mandibular function impairment questionnaire(MFIQ), neck disability index(NDI), visual analog scale(VAS), Beck depression inventory(BDI), stress reaction inventory(SRI) and Holmes & Rahe social readjustment rating scale(SRRS). Results : The contraction power of masseter muscle, upper trapezius, sternocleido-mastoid muscle and erector spinae by MEMG was significantly higher in the experimental group. The muscle fatigue of masseter muscle and sternodeido-mastoid muscle by MEMG was significantly higher in the experimental group. SRI was significantly higher in experimental group. There was no significant difference between two groups in the Jackson's angle, Cobb's method and cranio-cervical posture. Conclusions : The results suggest that temporomandibular disorder related mental stress but physical stress does not change cervical structure significantly.

• Journal of the Ergonomics Society of Korea
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• v.34 no.2
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• pp.151-165
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• 2015

Objective: This study aims to develop and scientifically investigate the efficacy of the Spine S-curve Reactive Backrest that responds to the spine curvature of the user when seated, and maintains and enhances the natural S-curve of the lower back, thereby helping to relieve fatigue, correct posture and prevent spine deformities. Background: The focus of current development, design guidelines and/or standards for office chairs is mainly placed on the chair's dimensions, incline angle, adjusting features and lumbar support. Research and development was called for developing a chair backrest that maintains and improves the S-curve of the full spine. Method: The Spine S-curve Reactive Backrest was ergonomically designed to maintain correct posture and enhance user comfort. When leaned on, the backrest responds to the user's spine line and the whole lower back sits closely against the backrest, thereby aligning the user's lower back and backrest as one to maintain and improve the natural S-curve formation of the spine. In order to evaluate the efficacy of the newly designed chair (new design) and the comparison target (chair), five male college students of standard body type with normal spine curvature were selected as test subjects, and a motion analyzer and electromyography were utilized to measure S-curve and erector spinae muscle activity when seated. Results: The spine S-curve was better maintained and improved when sitting in the new design than in the comparison chair. Particularly notable was the greater displacement gap of the thoracic spine than the cervical spine, and also that of the lumbar more than the thoracic spine, with the increase of the backrest tilting angle. Furthermore, the electromyogram results showed the new design caused a lower fatigue level of the erector spinae muscles compared to the comparison chair, and also earned a higher preference in the subjective opinion results. Conclusion: The newly designed chair in this study responds to the user's spine curvature and maintains and enhances the lower back's natural S-curve, and thereby relieves fatigue, promotes better posture, and helps to prevent spine deformities better than existing office chairs. There is a need to widely introduce and supply this new design. Application: The new design is applicable to office and student chairs, and is expected to improve concentration and work efficiency.

• Safety and Health at Work
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• v.9 no.3
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• pp.319-325
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• 2018

Background: Prolonged neck flexion during smartphone use is known as a factor of neck pain and alteration of neck muscle activity. Studies on the effects of shoulder taping on neck discomfort and neck muscle responses while texting on a smartphone are still lacking. The aim of this study was to examine the effects of shoulder taping on neck discomfort using a numerical rating scale, and neck muscle activity and fatigue using a surface electromyography during a texting task on a touchscreen smartphone. Methods: Twenty-five healthy adolescents used the dominant hand to perform a 30-minute texting task using a touchscreen smartphone at two separate times under one of the following two conditions: taping across the upper trapezius muscle and no taping. Neck discomfort, normalized root mean square, and normalized median frequency slopes for upper trapezius, cervical erector spinae, and sternocleidomastoid muscles were recorded. Results: The results revealed that shoulder taping provided significantly lower neck discomfort than no taping (p < 0.001). However, shoulder taping did not significantly alter normalized root mean square and normalized median frequency slope values of all muscles when compared with no taping controls. Conclusion: Shoulder taping reduces neck discomfort but does not affect neck muscle activity and fatigue while texting on a touchscreen smartphone.

• Physical Therapy Korea
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• v.30 no.3
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• pp.221-229
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• 2023

Background: In modern society, the use of computers accounts for a large proportion of our daily lives. Although substantial research is being actively conducted on musculoskeletal diseases resulting from computer use, there has been a recent surge in interest in improving the working environment for prevention. Objects: This study aimed to examine the effects of posture correction feedback (PCF) on changes in neck posture and muscle activation during computer typing. Methods: The participants performed a computer typing task in two sessions, each lasting 16 minutes. The participant's dominant side was photographed and analyzed using ImageJ software to verify neck posture. Surface electromyography (EMG) was used to confirm the participant's cervical erector spinae (CES) and upper trapezius muscle activities. The EMG signal was analyzed using the percentage of reference voluntary contraction and amplitude probability distribution function (APDF). In the second session, visual and auditory feedback for posture correction was provided if the neck was flexed by more than 15° in the initial position during computer typing. A 20-minute rest period was provided between the two sessions. Results: The neck angle (p = 0.014), CES muscle activity (p = 0.008), and APDF (p = 0.015) showed significant differences depending on the presence of the PCF. Furthermore, significant differences were observed regarding the CES muscle activity (p = 0.001) and APDF (p = 0.002) over time. Conclusion: Our study showed that the feedback system can correct poor posture and reduces unnecessary muscle activation during computer work. The improved neck posture and reduced CES muscle activity observed in this study suggest that neck pain can be prevented. Based on these results, we suggest that the PCF system can be used to prevent neck pain.

• Journal of Pharmacopuncture
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• v.7 no.2
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• pp.57-64
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• 2004

This study was carried to identify the component of Small Intestine Meridian Muscle in human, dividing the regional muscle group into outer, middle, and inner layer. the inner part of body surface were opened widely to demonstrate muscles, nerve, blood vessels and the others, displaying the inner structure of Small Intestine Meridian Muscle. We obtained the results as follows; 1. Small Intestine Meridian Muscle is composed of the muscle, nerve and blood vessels. 2. In human anatomy, it is present the difference between a term of nerve or blood vessels which control the muscle of Meridian Muscle and those which pass near by Meridian Muscle. 3. The inner composition of meridian muscle in human arm is as follows ; 1) Muscle ; Abd. digiti minimi muscle(SI-2, 3, 4), pisometacarpal lig.(SI-4), ext. retinaculum. ext. carpi ulnaris m. tendon.(SI-5, 6), ulnar collateral lig.(SI-5), ext. digiti minimi m. tendon(SI-6), ext. carpi ulnaris(SI-7), triceps brachii(SI-9), teres major(SI-9), deltoid(SI-10), infraspinatus(SI-10, 11), trapezius(Sl-12, 13, 14, 15), supraspinatus(SI-12, 13), lesser rhomboid(SI-14), erector spinae(SI-14, 15), levator scapular(SI-15), sternocleidomastoid(SI-16, 17), splenius capitis(SI-16), semispinalis capitis(SI-16), digasuicus(SI-17), zygomaticus major(Il-18), masseter(SI-18), auriculoris anterior(SI-19) 2) Nerve ; Dorsal branch of ulnar nerve(SI-1, 2, 3, 4, 5, 6), br. of mod. antebrachial cutaneous n.(SI-6, 7), br. of post. antebrachial cutaneous n.(SI-6,7), br. of radial n.(SI-7), ulnar n.(SI-8), br. of axillary n.(SI-9), radial n.(SI-9), subscapular n. br.(SI-9), cutaneous n. br. from C7, 8(SI-10, 14), suprascapular n.(SI-10, 11, 12, 13), intercostal n. br. from T2(SI-11), lat. supraclavicular n. br.(SI-12), intercostal n. br. from C8, T1(SI-12), accessory n. br.(SI-12, 13, 14, 15, 16, 17), intercostal n. br. from T1,2(SI-13), dorsal scapular n.(SI-14, 15), cutaneous n. br. from C6, C7(SI-15), transverse cervical n.(SI-16), lesser occipital n. & great auricular n. from cervical plexus(SI-16), cervical n. from C2,3(SI-16), fascial n. br.(SI-17), great auricular n. br.(SI-17), cervical n. br. from C2(SI-17), vagus n.(SI-17),hypoglossal n.(SI-17), glossopharyngeal n.(SI-17), sympathetic trunk(SI-17), zygomatic br. of fascial n.(SI-18), maxillary n. br.(SI-18), auriculotemporal n.(SI-19), temporal br. of fascial n.(SI-19) 3) Blood vessels ; Dorsal digital vein.(SI-1), dorsal br. of proper palmar digital artery(SI-1), br. of dorsal metacarpal a. & v.(SI-2, 3, 4), dorsal carpal br. of ulnar a.(SI-4, 5), post. interosseous a. br.(SI-6,7), post. ulnar recurrent a.(SI-8), circuirflex scapular a.(SI-9, 11) , post. circumflex humeral a. br.(SI-10), suprascapular a.(SI-10, 11, 12, 13), first intercostal a. br.(SI-12, 14), transverse cervical a. br.(SI-12,13,14,15), second intercostal a. br.(SI-13), dorsal scapular a. br.(SI-13, 14, 15), ext. jugular v.(SI-16, 17), occipital a. br.(SI-16), Ext. jugular v. br.(SI-17), post. auricular a.(SI-17), int. jugular v.(SI-17), int. carotid a.(SI-17), transverse fascial a. & v.(SI-18),maxillary a. br.(SI-18), superficial temporal a. & v.(SI-19).

• Journal of the Korea Convergence Society
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• v.9 no.11
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• pp.209-216
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• 2018

This study aimed to investigate the association of the muscle activity around the neck of the operator(dental hygienists') according to the change in the patient's neck angle during a direct visual inspection on the maxillary right-side molar palatal surface. The operators were $4^{th}$ year dental hygiene students, who are future dentalhy gienists, having accurate understanding on and awareness of the location of the operation site, hand fixation, and how to use the tools. Data on the change in the muscle activity around the neck were collected by using surface electromyography and neck goniometer. SPSS statistics 20 was used for statistical analyses including Shapiro-wilk test and one-way ANOVA. As a result, the activities of the operator upper trapezius, cervical erector spinae, and levator scapulae muscles significantly decreased when the patient's head was angled compared to when it was not. For the angle of the operator head, the head bend significantly decreased when the patient's head was angled than when it was not. Based on the study results, it is expected that angling the patient's head when treating his or her teeth will decrease the excessive muscle activity around the neck of the operator, and will reduce muscle fatigue. Therefore, angling the head of the patient while treating his or her teeth is recommended. This suggests that muscle pain caused by repetitive actions in the wrong posture can be reduced.