• 대한인간공학회지
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• 제20권2호
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• pp.71-82
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• 2001

Twisting posture in lifting tasks has been identified as a risk factor of low back pain. However, it has been usually estimated in terms of compressive stress or muscular activity. Thus, this study was conducted to predict the influence on muscular fatigue during lifting simulation. Fifteen young and healthy subjects were recruited and performed isometric trunk exertions during upright standing, two-level flexions and five-level asymmetric twisting conditions. EMG signals from five primary trunk muscles in right part of body were collected during 20sec for 45 different lifting conditions. RMS(root mean square) and MPF(mean power frequency) parameters were used to analyze the EMG signals. Twisting postures were significant in right erector spinae(ERSR), right latissimus dorsi(LATR), right internal oblique(INOR) for muscular activities. Especially, when trunk was $30^{\circ}$ CCW twisting posture. ERSR and INOR activities increased respectively by 11% and 3%. Regarding the trunk muscle fatigue, we found that MPF shifts in twisting posture increased 2.3 and 2.6 times for ERSR and INOR muscles respectively. Therefore, It is probable for workers to suffer from low back disorders when they were exposed to a extreme twisting posture during prolonged lifting. This study suggests NIOSH(National Institute for Occupational Safety and Health) lifting equation needs the time-duration multiplier in addition to asymmetric multiplier.

• 대한인간공학회지
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• 제28권3호
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• pp.81-85
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• 2009

Work related musculoskeletal disorders(WMSDs) was a leading cause of sick leave and injuries in the industries of our country. Posture was an important consideration in the design of work method and workplaces, because it affected the ability of workers to use various equipments and influenced how long they could perform their job without feeling discomfort, fatigue, and musculoskeletal disorders. Imbalanced lower limb postures such as a squatting posture were awkward working postures common to the shipbuilding shops, farms, automobiles assembly lines in our country. Different awkward working postures were known to be associated with specific musculoskeletal disorders. Eight postures in lower limb postures divided into balanced and imbalanced postures were evaluated by electromyographic(EMG) activity for lower limb muscles. Twelve male subjects participated in this study. This paper was to analyze the effects of lower limb muscles workload according to lower limb postures(knee angle) and working time. The ANOVA results showed that most EMG root mean square(RMS) values were statistically significant effect according to lower limb postures(knee angle) and working time. Therefore, the results of this study will provide the basis to evaluate workload of lower limb postures correctly adopted by workers in various jobs and the ergonomic reference to prevent WMSDs.

• 대한인간공학회지
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• 제32권3호
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• pp.273-278
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• 2013

Objective: This study aims to analyze and evaluate fatigue in upper trapezius muscles of adults when inputting text on a smart phone, thereby examining the risk of cumulative trauma disorders in the musculoskeletal system of the upper extremity. Method: Forty-five healthy adults were divided equally into three groups: a smartphone group, a notebook group, and a desktop group. A surface electromyogram was placed on the upper trapezius muscle of each participant, after which they inputted text for ten minutes within an ergonomic setting; their side posture was recorded on video and analyzed. Results: The spectral edge frequency values for the smartphone group, as recorded from the upper right trapezius muscles on the surface electromyogram, showed a significant decrease(p<.05). Regarding the RULA, all three groups had results indicating "action level 2". Conclusion: All three groups had results indicating "action level 2" according to the RULA, which means that additional research on the posture of the participants while performing tasks is necessary, and their posture needs to be corrected. In particular, the smartphone group has the highest levels of fatigue in the upper trapezius muscles, suggesting that the task of inputting text on a smartphone is a high risk for causing cumulative trauma disorders.

• Journal of Oral Medicine and Pain
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• 제7권1호
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• pp.47-58
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• 1982

The author has studied on the clinical features and symptomatology of 97 MPDS patients, who visited the Dept. of Dentistry, Kyungpook National University, from January to September in 1982. The results were as follow : In age and sex distribution of patients in this population, the third decades appeared to have the highest prevalence and the male to female ratio was almost 1 to 2.23. As to occupation, students and housewives were revealed to have the highest incidence of MPDS. The chief complaints of patients were pains, TMJ noises, and limitation of mouth opening in order of frequency, and the most prevalent site of symptom was that of preauricular area. In symptom sequence, the majority of initial symptoms were TMJ noise and pain but limitation of mandibular movement was progressively developed, regardless of nature of early symptoms. Chronic unfavorable oral habits were found to be the most possible predisposing factors in this study. The average maximum interincisal distance was $38.13\pm10.00mm$ in males and $30.73\pm8.75mm$ in females, and a deviation of mandible during mouth opening was observed in 60.8% of patients. In TMJ signs, tenderness of the TMJ to palpation was found in 60.8% of patients and TMJ noise was audible in 50.5% of patients with a stethoscope. The muscles of masticatory system were palpated according to usual methods, and a significant indidence of muscular tenderness was present, with the lateral pteygoid muscles being most frequently involved, followed by masseter, medical pterygoid and temporalis muscles.

• PNF and Movement
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• 제17권3호
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• pp.401-409
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• 2019

Purpose: This study investigated the muscular activity of abdominal muscles during a variety of plank exercises following changes in the leg and head positions. Methods: Thirty healthy individuals participated in this study. They performed six variations of plank exercises, including three changes in head position and two changes in leg position. Each plank was defined as head neutral-leg neutral, head up-leg neutral, head down-leg neutral, head neutral-leg wide, head up-leg wide, and head down-leg wide. During the plank excises, the muscle activities of the rectus abdominis, internal oblique, erector spinae, and upper trapezius were measured. Results: The head down position significantly increased the rectus abdominis activity compared to other head positions (p<0.05). On the other hand, the upper trapezius muscle activity was significantly higher with the head up position compared to other head positions (p<0.05). Regardless of head positions, both the rectus abdominis and internal oblique muscles were significantly activated with leg wide position compared to the leg neutral position (p<0.05). Conclusion: Head and leg positions could change the muscular activities of abdominal muscles during plank exercises. For example, the head down position is effective for activating the rectus abdominis while the leg wide position could be advantageous for enhancing the internal oblique and rectus abdominis.

• 한국전문물리치료학회지
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• 제16권3호
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• pp.16-23
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• 2009

The purpose of this study was to investigate the effects of a repetitive lifting task on the level of activation and median frequency of the paraspinal muscles, and to provide basic data of the maximal acceptable duration of the lifting task to avoid muscle fatigue. Ten healthy male subjects were recruited as participants and they repetitively (12 lifts/min) lifted a box ($46cm{\times}30cm{\times}30cm$, 15 kg) for 10 minutes. Electromyographic data (muscle activation and median frequency), heart rate, and Borg CR10 score were recorded at 1, 3, 5, 7, and 9 minutes after the lifting task. Electromyographic data was recorded from the elector spinalis, mutifidus, external oblique abdominis, and rectus abdominis for 1 minute. The results showed that as the repetitive lifting task progressed, the heart rate and Borg CR10 score significantly increased. In addition, activation of the muscles increased. The median frequency significantly decreased over time in the elector spinalis, mutifidus, and external oblique abdominis (right side), except for the external oblique abdominis (left side) and rectus abdominis. It is suggested that the median frequency recorded from a dynamic task is used to monitor muscle fatigue. Furthermore, the repetitive lifting task (15 kg, 12 lifts/min) should not continue for more than 3 minutes in order to avoid muscle fatigue.

• 한국안전학회지
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• 제28권1호
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• pp.81-87
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• 2013

Crane operators usually work with their necks bent forward in a seating position for a long period. They have complained of their musculoskeletal stress at their necks. The objective of this study was to find the level of stress at the neck when crane operators bend their neck forward during their work. Experiments were conducted in the laboratory where subjects bent their necks forward for 1 minute and took a rest for 0.5 minute and repeated this performance for 60 minutes. Subjective evaluation using Borg's CR-10 scale and electromyography (EMG) were used to check the level of the stress at the neck. Subjects reported that the level of pain at the end of 60 min. experiment was close to the extreme pain(level 8.95). The EMG level(amplitude) increased 80% on the average and the center frequency of EMG shifted to the lower frequency level which indicated fatigue of neck muscles. Thus, it was found that there is quite much neck stress for crane operators when they maintain their neck posture of bending forward for a long time during their work. This information will be a basis in searching for an intervention measure for the crane operators' neck stress.

• 한국정보통신학회논문지
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• 제16권5호
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• pp.932-938
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• 2012

얼굴 표정은 상호간 의사소통에 있어 중요한 의미를 갖는 것으로, 인간이 사용하는 다양한 언어보다도 수많은 인간 내면의 감정을 표현할 수 있는 유일한 수단이다. 본 논문에서는 쉽고 자연스러운 얼굴 표정 생성을 위한 근육 모델 기반 3D 얼굴 표정 생성 시스템을 제안한다. 3D 얼굴 모델의 표정 생성을 위하여 Waters의 근육 모델을 기반으로 자연스러운 얼굴 표정 생성에 필요한 근육을 추가하여 사용하고, 표정 생성의 핵심적 요소인 눈썹, 눈, 코, 입, 볼 등의 특징요소들을 중심으로 얼굴 근육과 근육벡터를 이용하여 해부학적으로 서로 연결된 얼굴 근육 움직임의 그룹화를 통해 얼굴 표정 변화의 기본 단위인 AU를 단순화하고 재구성함으로써 쉽고 자연스러운 얼굴 표정을 생성할 수 있도록 하였다.

• The Korean Journal of Pain
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• 제6권1호
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• pp.83-95
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• 1993

In out-patient clinic, it seems to be common that most back pain arise from muscular origins rather than from skeletal origins. Most physicians have wished to diagnose lower back pain from the radiologic findings only. From clinical experiences and anatomical studies, I have gotten a different opinion from common sense about backaches. If I met a patient who had lower back pain around the posterior superior iliac crest(P.S.I.C.) area, I would had to search a trigger point in the erector spinae muscles at the level of thoraco-lumber junction rather than at the level of the painful site. It is why that sensory innervation over the posterior superior iliac crest area is the posterior primary branch of T12 spinal nerve running down through the erector spinae muscles. Pain on the iliac crest area is supposedly due to hyperirritability of the sensory nerve distributing to this area. Hyperirritability of the posterior primary branch of $T_{12}$ spinal nerve may be due to the spasm of the longissimus thoracis muscle in the erector spinae muscles at the level of the thoraco-lumbar junction. So finally, I would like to insist that spasmolytic treatment on the muscle at the level of the thoraco-lumbar junction would be better for pain relief around P.S.I.C. than treatment at the painful site only.

• 한국운동역학회지
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• 제23권3호
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• pp.279-284
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• 2013

The purpose of this study was to determine the effect of head posture and respiratory pattern on muscle activities of sternocleidomastoid (SCM) and scalene during maximal respiration. The seventeen subjects with upper-costal breathing pattern were participated in this study. Surface electromyography was used to measure the muscles activities of SCM and scalene. The volume and velocity of inspiration were monitored by using the spirometer in each subject. Each subject was performed the 3-cycle of respiration in each condition. The mean values of three peak muscle activity in each muscle were used in the data analysis. A2 (head posture: forward head posture: FHP vs. neutral posture) X 2 (breathing pattern: costal vs. diaphragmatic) repeated-measures analysis of variance (ANOVA) was used to compare the normalized muscle activities of the SCM and scalene. The results showed that the muscle activities of SCM and scalene in diaphragmatic breathing were significantly lower than those in costal breathing for each head posture (p<.0125). The muscle activities of SCM in neutral position were lower than those in forward head position during costal breathing (p<.0125). The diaphragmatic breathing in neutral position of head is recommended to decrease the tension of the accessory inspiratory muscles during respiration in neck-pain patients with FHP.