• 대한인간공학회지
• /
• 제30권6호
• /
• pp.695-703
• /
• 2011

Objective: This study was to investigate the effects of coordinated upper-limb body postures on the subjective discomfort rating, heart rate, and muscle activities. Background: Although generally many checklists such as OWAS, RULA, and REBA were applied to evaluate various body postures, the body postures were might be overestimated or underestimated because each body part(i.e., back, shoulder, and elbow etc.) was evaluated separately, and then added all rates of individual body parts to assess an overall risk level for the body posture in these methodologies. Methods: A total of 20 participants maintained 14 postures which were combinations of back, shoulder, and elbow flexion angles and then muscle activities, subjective discomfort, and heart rates were collected every three minute during a sustained 15 minute and 0.5kg weight holding task. Four muscle groups were investigated: erector spine, anterior deltoid, upper trapezius, triceps brachii. Results: Results showed that subjective discomfort was the lowest when the angle of back and shoulder were both $0^{\circ}s$, while the body posture with $45^{\circ}$ of back angle and $45^{\circ}$ shoulder angle was rated as the most subjective discomfort posture. In general, the subjective discomfort ratings increased as back and shoulder flexion angles increased. It was noted that, however, the subjective discomfort of body posture with a $45^{\circ}$ back angle and $45^{\circ}$ shoulder flexion angle was lower than that of body posture with a $0^{\circ}$ back and $45^{\circ}$ shoulder flexion angle. The research findings of heart rates and muscle activities showed similar results for the analyses of subjective discomfort ratings. Conclusions: The possible limitations of the current ergonomics evaluation techniques which assessing a body posture with summing all body part score after individually analyzed in this study. Based on the analyses of subjective discomfort, heart rate, and muscle activities, it was recommended that a use of effects of coordinated upper-limb body postures would be considered when one evaluates work-load for various working postures. Application: These findings can be used for developing a more accurate assessment checklist for working posture as well as preventing musculoskeletal disorders of workers in workplaces.

• 대한인간공학회지
• /
• 제28권1호
• /
• pp.9-19
• /
• 2009

Repetitive movement, inadequate working posture, overuse of force, physical contact with sharp edge, vibration and temperature were well known risk factors of WMSDs (Work-related Musculoskeletal Disorders). Many researchers have investigated the relationship between inadequate working postures and incidences of WMSDs of the upper extremities, whereas relatively few researchers have tried to evaluate workload associated with the lower-body postures. The effects of lower-limb postures including various knee flexion angles on the subjective discomfort, heart rate and EMG of lower-limb muscles were investigated in this study. Thirty graduate students were asked to maintain thirteen different body postures, and heart rate and EMG data of five muscle groups (electro spine, biceps femoris, vastus medialis, gastrocnemius and tibialis anterior) from each posture were collected during fifteen minutes sustaining tasks. All participants were also asked to report their discomfort ratings of body parts. Results showed that high subjective discomfort ratings and heart rates were reported at the postures of knee angles of $60^{\circ}$ and $90^{\circ}$, whereas low discomfort ratings were founded at the postures of chair heights with 20cm, 40cm, and sitting with crossed legged. The change of median frequency for each muscle group during fifteen minutes tasks was investigated for each body posture to evaluate the relationship between muscle fatigue and body posture. It was found that the trends of changes of median frequency were different based on muscle group as well as lower-limb body posture from this study.

• 대한인간공학회지
• /
• 제31권5호
• /
• pp.609-616
• /
• 2012

Objective: The aim of the study is to evaluate the difference of legibility between e-book and paper-book by using eye-tracker. Background: Despite of many researches on the e-book and paper-book, there are few researches on the difference between e-book and paper-book. In addition, the researches on the e-book were only dependent on the e-book reader. This study focused on the comparison of e-book and paper-book controlled with the same environments. Method: This study was conducted with $2{\times}3$ within-subject design. Independent variables include the types of book (e-book, paper-book) and font sizes (8pt, 10pt, 12pt). Dependent variables are four measures of fixation duration, saccade length, blink rate and subjective discomfort. Analysis of Variance (ANOVA) with repeated measured design was used to investigate the main and interaction effects of independent variables on each of the dependent variables. The multiple comparisons were performed by post hoc analysis and Bonferroni correction was applied. Results: Fixation duration at e-book was longer than paper-book (p<0.01). Saccade length at e-book was shorter than paper-book (p<0.05). Blink rate at e-book was higher than paper-book (p<0.1). Subjective discomfort at e-book was higher than paper-book (p<0.1). Legibility at 8pt was better than 10pt, 12pt (p<0.01) in fixation duration, saccade length and subjective discomfort. Conclusion: It was found that the legibility at e-book are worse than paper-book from this study. These results indicated that the legibility of e-book was needed to be validated and improved to replace the paper-book. Application: This study suggests improving something related to fixation duration, saccade length, blink rate and subjective discomfort for betterment of e-book.

• 대한통합의학회지
• /
• 제10권4호
• /
• pp.35-47
• /
• 2022

Purpose : As the number of patients with systemic diseases is increasing in the old, the relevance of oral health is gaining particular research interest. To provide fundamental resources for dental services, this study examined the relationship between doctors' diagnoses of circulatory diseases and patients' awareness of oral health and oral care behaviors. Methods : SPSS 26.0 was used to assess various variables, including doctor's diagnosis of circulatory diseases, gender, age, household income quintile, participation in economic activity, marital status, subjective level of oral health awareness, mastication discomfort, speaking and chewing discomfort, dental inspection, use of oral care goods, teeth brushing during the previous day, and untreated oral conditions. Results : The circulatory diseases suffered by the subjects were as follows: 56 % high blood pressure, 36 % dyslipidemia, 6 % stroke, and 8 % myocardial infarction or angina. A higher age meant a higher diagnosis rate of high blood pressure (p<.001) and stroke (p<.001). Those with dyslipidemia showed a higher rate of receiving oral inspection (p=.040), and an untreated oral condition was more frequently observed among those not diagnosed with the disease (p=.035). The subjects who were not diagnosed with stroke showed a higher rate of oral inspection (p<.001), while those who had a prior experience of stroke suffered a higher rate of mastication discomfort (p=.020). People who had high blood pressure showed a lower rate of using oral care goods (p<.001), and those diagnosed with stroke showed a lower rate of brushing teeth the previous day. Conclusion : This study found a correlation between the diagnosis of circulatory diseases and the awareness of oral health and oral care behavior. Consequently, oral health education should be included in mental health-related education, and customized training to teach teeth brushing and the use of oral care goods should be provided to patients with circulatory diseases during dentist visits.

• 대한인간공학회지
• /
• 제32권6호
• /
• pp.549-555
• /
• 2013

Objective: The purpose of this study was to compare the performance of drilling on the ceiling in three different postures (standing, standing on the ladder and supine on the height adjusted board) and the subjective responses of perceived discomfort after the drilling. Background: Overhead work has been identified as a major occupational risk factor and has been a main research subject. Method: Ten young participants drilled 20 holes at the pre-marked places on the ceiling in three different postures. The drilling duration, resting and drilling heart rate were measured. The levels of perceived discomfort at neck, shoulder, elbow, hand and overall body were asked at the end of each task. Results: The working posture affected the heart rate after the drilling. Perceived discomfort in the neck decreased significantly in supine compared to drilling on the ladder. Conclusion: The results of this study suggest that drilling in supine can be an alternative way to reduce the drilling heart rate and the level of perceived discomfort in the neck without sacrificing the productivity. Application: The results of this study would be considered when drilling on the ceiling is required in construction workers.

• 한국안전학회지
• /
• 제16권1호
• /
• pp.73-78
• /
• 2001

It has been proposed that the acceptable level of discomfort was a valid measure of postural loading. Although the number of women employees has increased at a much faster rate than men workers did and female workers are thought to be more vulnerable to musculoskeletal disorders, most previous studies dealt with perceived discomforts for joint motions focused on male subjects. This study aims to measure perceived discomfort ratings of females for static joint motions. Ten female subjects participated in the experiment measuring perceived discomforts, in which almost every possible joint motion was included and the free modulus method of the magnitude estimation was employed. The results showed that discomfort levels were dependent on the joint motions and joints, and subjective discomfort ratings of women were significantly larger than those of men.

• Journal of Periodontal and Implant Science
• /
• 제47권4호
• /
• pp.240-250
• /
• 2017

Purpose: The aim of this study was to analyze the prevalence and risk indicators of peri-implantitis in Korean patients with history of periodontal disease. Methods: A total of 444 patients with 1,485 implants were selected from patients who had been treated at the Department of Periodontology, Chonbuk National University Dental Hospital between July 2014 and June 2015. A group with a history of peri-implantitis (HP) (370 patients with 1,189 implants) and a group with a current peri-implantitis (CP) (318 patients with 1,004 implants) were created based on the radiographic and clinical assessments of implants. The prevalence of peri-implantitis was calculated at both the patient and implant levels. The influence of risk variables on the occurrence of peri-implantitis was analyzed using generalized estimating equations analysis. Results: The prevalence of peri-implantitis in the HP and CP groups ranged from 6.7% to 19.7%. The cumulative peri-implantitis rate in the HP group estimated with the Kaplan-Meier method was higher than that in the CP group over the follow-up period. Among the patient-related risk variables, supportive periodontal therapy (SPT) was the only significant risk indicator for the occurrence of peri-implantitis in both groups. In the analysis of implant-related variables, implants supporting fixed dental prosthesis (FDP) and implants with subjective discomfort was associated with a higher prevalence of peri-implantitis than single implants and implants without subjective discomfort in the HP group. The presence of subjective discomfort was the only significant implant-related variable predictive of peri-implantitis in the CP group. Conclusions: Within the limitations of this study, the prevalence of peri-implantitis in Korean patients with a history of periodontal disease was similar to that reported in other population samples. Regular SPT was important for preventing peri-implantitis. Single implants were found to be less susceptible to peri-implantitis than those supporting FDP. Patients' subjective discomfort was found to be a strong risk indicator for peri-implantitis.

• 한국안광학회지
• /
• 제19권2호
• /
• pp.153-162
• /
• 2014

목적: 본 연구에서는 건성안이 일회용 써클소프트렌즈(이하 써클렌즈)의 권장착용시간을 초과하여 하루 이상 착용하였을 때 나타나는 자각적 및 타각적 변화와 렌즈 가시광선투과율의 변화에 대하여 알아보고자 하였다. 방법: 서로 다른 재질(hilafilcon B, nelfilcon A 및 etafilcon A)의 3가지 일회용 써클렌즈를 눈물량이 정상보다 적은 20대의 건성안(30안)에게 착용시키고 자각적 불편감, 착용자의 순목횟수, 각막에서의 렌즈중심안정위치 및 렌즈 가시광선투과율을 렌즈 착용직후와 착용자가 자각적 불편감의 증가로 더 이상 렌즈를 착용하지 못하였을 때에 각각 측정한 후 비교하였다. 결과: 일회용 써클렌즈의 재질에 따라 차이는 존재하였지만 10시간 이상 착용하였을 때부터 자각적 불편감을 호소하며 렌즈착용을 중단하였다. 그러나 비이온성 써클렌즈의 경우는 40시간 이상을 착용하는 건성안도 20% 정도로 나타났다. 건성안은 세 가지 재질 가운데 etafilcon A 재질 써클렌즈의 초과착용 시 가장 민감하게 자각적 불편감을 느끼는 것으로 나타났다. 써클렌즈 착용중단시점에서 대표적인 자각적인 불편감은 이물감, 뻑뻑함, 건조감 및 피곤함이었다. 일회용 써클렌즈를 초과착용하였을 때 순목횟수는 착용직후와 비교하여 렌즈재질에 관계없이 약 20~30%정도 통계적으로 유의하게 증가하였다. 렌즈착용 직후보다 착용 마지막 날에서 수직방향의 렌즈중심안정위치는 동공중심에 가까워졌으나 수평방향은 그 분포가 넓게 나타났으며, 특히 etafilcon A 재질 렌즈의 경우는 중심잡기가 불안정하였다. 또한 새 렌즈와 비교했을 때 초과착용한 후 렌즈의 가시광선투과율은 세 종류 렌즈 모두에서 평균적으로 15%가량 감소하였다. 결론: 이상의 결과에서 건성안에서 일회용 써클렌즈의 초과착용은 건조감과 뻑뻑함을 증가시켜 과도한 이물감을 느끼게 되며, 이는 가시광선투과율의 감소와 더불어 순목횟수의 유의한 증가를 유발하고 궁극적으로는 렌즈중심안정위치의 이탈을 초래함을 알 수 있었다. 또한 개인 및 렌즈재질에 따라서 정도의 차이는 있었으나 건성안은 정상안보다 고함수, 이온성렌즈의 초과착용에 자, 타각적으로 예민하게 반응함을 밝혔다. 따라서 본 연구결과는 건성안의 써클렌즈 착용으로 유발될 수 있는 문제점 및 부작용의 교육을 위한 기초 자료로 제시될 수 있다.

• 한국산학기술학회논문지
• /
• 제13권1호
• /
• pp.264-273
• /
• 2012

중 고등학교 교사의 근골격계 불편증상과 관련 요인을 알아보기 위해 2010년 10월 1일부터 10월 15일까지 250명의 교사들을 대상으로 근골격계 불편증상 설문조사를 실시하고, 231명(남자 68명, 여자 163명)의 결과를 신체 각 부위별로 통계분석 하였다. 근골격계 불편증상의 관련요인으로 특히 주관적 건강상태가 높은 연관성을 보였고(OR 11.75, 95% CI, 3.56-38.78), 그 외 근무학교유형, 40세 이상, 2시간 이상의 가사노동시간, 8시간 이상의 VDT작업시간, 휴식여부가 유의한 상관성이 있는 요인들로 분석되었다. NIOSH 기준에 의한 근골격계 불편증상 호소율은 36.8%였고, 각 부위별 불편증상 호소부위와 빈도는 목 60명(26.0%), 어깨 70명(30.0%), 팔/팔꿈치 16명(6.9%), 손/손가락 31명(13.4%), 허리 35명(15.2%), 다리/발 17명(7.4%)으로 목과 어깨의 발생빈도가 높았다. 목 부위는 주관적 건강상태와 휴식유무, 어깨부위는 주관적 건강상태와 성별, 손/손가락 부위는 연령, 허리부위는 주관적 건강상태와 연령, 다리부위는 주관적 건강상태와 연령, VDT작업시간이 관련성 있는 요인들로 분석되었다. 사무직근로자에서 근골격계 질환은 간단한 스트레칭만으로도 예방 가능하다. 신체 각 부위별로 간단하고 적절한 운동을 통해 자신의 건강상태를 유지하고 올바른 작업 자세와 작업요건을 갖추고 작업시간 중간에 충분한 휴식시간을 가짐으로써 직무로 인한 근골격계의 과도한 긴장과 불편감 발생을 낮추기 위한 스스로의 노력이 필요하다.

• 대한인간공학회지
• /
• 제32권6호
• /
• pp.511-516
• /
• 2013

Objective: The objective of this study is designing an optimal hand tool through maximum grip force study accordance to the hand grip span. Background: In order to prevent musculoskeletal diseases, studies on hand tool design are proceeding based on grip strength, finger force, and contribution of individual finger force on total grip strength. However, experimental apparatus using a tool that is actually used in work place was almost non-existent. Method: 19 males were participated in an experiment. Using the load cell inserted real plier, finger force, grip strength, and subjective discomfort rate of both hands (dominant and non-dominant) were measured in 5 different hand grip span(45mm, 50mm, 60mm, 70mm, and 80mm). Results: There was significant difference(p<0.001) of total grip strength, individual finger force and subjective discomfort rating according to various hand grip span(45, 50, 60, 70, and 80mm). Also, statistically significant different(p<0.001) was shown between the dominant hand and non-dominant hand. In addition, individual finger force in maximum grip was in order of middle finger, ring finger, index finger, and little finger. Conclusion: Optimal grip span of pliers that exerting maximum grip strength is 50~60mm. Application: This finding is expected to be used for designing proper pliers.