• Korean Journal of Applied Biomechanics
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• v.24 no.4
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• pp.375-383
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• 2014

The purpose of this study was to assess the inter-segmental trunk motion during which multi-segmental movements of the spinal column was designed to interpret the effect of segmentation on the total measured spine motion. Also it analyzed the relative motion at three types of the spine models in drop landing. A secondary goal was to determine the intrinsic algorithmic errors of spine motion and the usefulness of such an approach as a tool to assess spinal motions. College students in the soccer team were selected the ten males with no history of spine symptoms or injuries. Each subject was given a fifteen minute adaptation period of drop landing on the 30cm height box. Inter-segmental spine motion were collected Vicon Motion Capture System (250 Hz) and synchronized with GRF data (1000 Hz). The result shows that Model III has a more increased range of motion (ROM) than Model I and Model II. And the Lagrange energy has significant difference of at E3 and E4 (p<.05). This study can be concluded that there are differences in the three models of algorithm during the phase of load absorption. Especially, Model III shows proper spine motion for the inter-segmental joint motion with the interaction effects using the seven segments. Model III shows more proper observed values about dynamic equilibrium than Model I & Model II. The findings have shown that the dynamic stability strategy of Model III toward multi-directional spinal motion supports for better function of the inter-segmental motor-control than the Model I and Model II.

• IE interfaces
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• v.10 no.3
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• pp.197-208
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• 1997

In workplace design, an ergonomic solution should ensure low postural stress in the operator during his/her work. Stress caused by awkward working postures of the trunk, shoulders and legs can result in fatigue, discomfort, musculo-skeletal disorders and nerve entrapment syndromes. Since discomfort and musculo-skeletal disorders are both related to exposure to biomechanical load on the musculo-skeletal system, minimization of discomfort will contribute to reduction of the risk for musculo-skeletal disorders as well. Therefore, in this study, perceived discomfort on the human body joints was measured in the standing postures using the magnitude estimation in order to have a standardized numerical scale for joint discomfort. Nine healthy graduate students participated voluntarily in the laboratory study. The results revealed that perceived discomfort of all the joints increased as the joints deviated from neutral position. Especially, it showed drastic increment on perceived discomfort when deviation from neutral position in each human body joint increased from 75% to 100%. in terms of relative range of motion(R0M). On the basis of these experimental results, a preliminary ranking for assessment of stressfulness of non-neutral postures around the human body joints was suggested.

• Journal of Korean Society of Forest Science
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• v.112 no.3
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• pp.303-321
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• 2023

To develop the Forest Work Load Index (FWLI) for estimating the work intensity of forest workers, a study focused on forest tending was conducted. To estimate the FWLI, we used the Ovako Working Posture Analysis System (OWAS) and the Work Load Index (WLI). The OWAS is a prominent method used for analyzing musculoskeletal load in work tasks, and WLI is a prominent method used for analyzing the work intensity of workers. The PRI values analyzed for each forest tending project were 185.3 (Thinning), 150.6 (Pruning), 181.1 (Thinning for Forest Fire Prevention), and 197.0 (Thinning for Young Trees). The WLI values, calculated on the basis of the measured heart rates, were 59.5% (Thinning), 53.5% (Pruning), 56.2% (Thinning for Forest Fire Prevention), and 62.3% (Thinning for Young Trees). The FWLI was calculated using the analyzed PRI and WLI values. The FWLI values for the forest tending project were 110.2 (Thinning), 80.7 (Pruning), 102.1 (Thinning for Forest Fire Prevention), and 123.0 (Thinning for Young Trees). The FWLI developed in this study can be used to quantitatively compare the workloads of forest workers. In the future, the analyzed FWLI can be used as a basis for improving forest workers' postures and comparing workloads across different forest projects.

• Journal of the Korean Society of Physical Medicine
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• v.7 no.1
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• pp.69-75
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• 2012

Purpose : The study was designed to investigate analysis of kinematics of lower extremity in healthy adults during walking with external loads on trunk. Methods : Fifteen healthy adults were recruited and The subjects provided written and informed consent prior to participation. They walked on a ten-meter walkway at a self-selected pace with loads of 0, 5, 10, and 15kg. They completed three trials in each condition and kinematic changes were measured. A three-dimensional motion analysis system was used to analyze lower extremity kinematic data. The data collected by each way of walking task and analyzed by One-way ANOVA. Results : There were significant differences in hip and knee joint on saggittal plane at initial contact and preswing, and significant differences in ankle joint on transverse plane at preswing. Conclusion : These findings revealed that increased external loads were changed joint angles and influenced postural strategies because of kinematic mechanism and future studies is recommended to find out prevention from damage of activities of daily living.

• Journal of Korean Physical Therapy Science
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• v.18 no.4
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• pp.65-72
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• 2011

The purpose of this study was to investigate the responses of the trunk muscle during expected and unexpected sudden loadings of the hands on the sagittal plane. Twenty, young healthy adults(male 10, female 10) were participated to two different loading conditions : expected and unexpected sudden loadings. Different weights were dropped in hand : 5lb, 6lb, 7lb for male, and 3lb, 4lb, 5lb for female. EMG activity of rectus abdominalis and erector spine muscle were collected. Rectus abdominalis and lumbar erector spine muscle activity significantly increased in unexpected sudden loadings than expected sudden loadings(p<.05). This results indicate that co-contraction of abdominal and back muscle contribute for dynamic spinal stability during expected or unexpected activities of daily living. Preparatory adjustments can be made which reduce the postural perturbation to sudden load and prevent low back injuries.

• Bulletin of the Korean Institute for Industrial Safety
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• v.3 no.1
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• pp.11-17
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• 2003

In recent years, work-related musculoskeletal disorders (WMSDs) are one of major issues in occupational safety and health in Korea, since the number of injured workers has rapidly increased and the related regulation was amended to improve the work conditions. Main risk factors of WMSDs in Korean industries include manual handling of heavy weight loads, awkward postures, repetitive tasks, prolonged static muscle contraction, and so on. in this article, some ergonomics case studies for identifying the risk factors of WMSDs and far their prevention were introduced. They include a biomechanical analysis for the heavy-weight handling task in a machine-repair shop, physiological evaluation of backpack-carrying tasks in a beverage delivery job, and a set of psychophysical studies to evaluate static-postural load. These studies showed that there are several different ergonomic approaches to identifying and evaluating risk factors of WMSDs and to eliminating them or reducing their levels, and that it is important to select proper methods and apply them in improving the work conditions according to the characteristics of the task. In addition, it needs to develop practical and effective ergonomic tools to prevent WMSDs and to provide these tools to the safety managers in the field so that they can improve the tasks by themselves.

• Journal of the Korea Safety Management & Science
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• v.26 no.2
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• pp.87-92
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• 2024

This study aims to compare six observational methods for assessing arm- and hand-intensive tasks, based on literature review. The comparison was conducted in viewpoints of body regions, force/external load, motion repetition, other factors including static posture, coupling, duration/break, pace, temperature, precision task, and final risk or exposure level. The number of risk factors assessed was more, and assessment procedure was more complex than the observational methods for assessing whole-body postural loads such as Ovako Working Posture Analysis System(OWAS), Rapid Upper Limb Assessment(RULA), and Rapid Entire Body Assessment(REBA). Due to these, the intra- and inter-reliabilities were not high. A past study showed that while Hand Arm Risk Assessment Method(HARM) identified the smallest proportion of the work tasks as high risk, Strain Index(SI) and Quick Exposure Check(QEC) hand/wrist were the most rigorous with classifying most work tasks as high risk. This study showed that depending on the observational technique compared, the evaluation factors, risk or exposure level, and evaluation results were different, making it necessary to select a technique appropriate for the characteristics of the work being assessed.

• The korean journal of orthodontics
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• v.24 no.4 s.47
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• pp.917-932
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• 1994

This study was conducted to examine the changes in the shape of the Sprague-Dawley rats' articular disk following postural hyperpropulsion by observing their articular specimens through light and electronic microscopes after following 2-week and 4-week postural hyperpropulsion from their four weeks of age. The findings of this study are summarized as follows. It was shown that as compared with the control group, the experimental group indicated a significant increase in thickness of the 2-week groups' anterior and postreior portion of the articular disc. The experimental group showed statistically more significant increase in thickness of the 4-week groups' anterior portion of the articular disc than the control group. Light micrograph showed that the experimental group had more fibroblast in the anterior portion of the 2-week and 4-week groups than the comparing group. The 2-week groups showed in the findings through the electronic microscope that there were found the well developed and dilated RER which seems to actively synthesize the extracellular matrix including collagen, the cells with the well developed RER without distention which seems to actively synthesize the intracellular microfilaments due to the well developed free ribosome, and the typical chondroid cells. In addition, there was more fibroblast cell with the distended and well developed RER in the anterior area of the experimental group than that of the control group. The 4 week experimental group's anterior area of the disk had more cells than that of the control group while fibroblast with the well developed RER and free ribosome was quite abundat. Based on the above result of this study, it was shown that the functional hyperpropulsion of the mandible causes the changes in the nature of the mechanical load to the certain portion of the articular disk. As a result, it seems that there may be occurred some changes in morphology of the disc by adaptation or confrontation with these changes at the cellular level.

• Journal of the Ergonomics Society of Korea
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• v.19 no.2
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• pp.15-31
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• 2000

The aim was to evaluate the prevailing ergonomic and psychosocial conditions regarding low back injury in an automobile assembly system. This study consisted of two parts. In the first part of the study, analytic biomechanical model and NIOSH guidelines were applied to evaluate risk levels of low back injury for automobile assembly jobs. Total of 246 workers were analysed. There were 20 jobs having greater back compressive forces than 300kg at L5/S1. Also, there were 44 jobs over Action Limit with respect to 1981 NIOSH guidelines. This might in part be explained by the ergonomic conditions of the company analysed generally being good, with a relatively low duration of 'combined' extreme work posture. The relationship between psychosocial factors and low back injury was examined in the second part of the study. It has recently been recognized that overall reaction to working conditions was influenced by a range of factors, some of which were physical and some psychosocial. The psychosocial environment surrounding the work place may contribute to the perception of risk and eventual ill-health. A battery of questionnaires concerning the psychosocial stress based on PWI(Psychosocial Well-being Index) and musculoskeletal pain symptoms at low back was completed by 246 workers at the same plant. Results showed that 207 out 246 workers experienced the symptoms and 27 workers were diagnosed as patients. Two groups(low stressed, high stressed) based on PWI score had no significant relationships with both symptoms and results of diagnosis. However, sensitivities for symptoms and diagnosis by PWI were 91.3% and 92.6% respectively. Finally, relationships between physical work load and psychosocial stress were analysed. Specifically, some postural factors {vertical deviation angle of forearm, horizontal deviation angle of upperarm, vertical deviation angle of thigh, etc) were highly correlated with psychosocial stress. The results illustrated that PWI scores were associated with some physical workloads. However, psychosocial stress levels couldn't be well related with the pain symptom as well as the actual incidence of low back injury since pain or discomfort regarding low back injury were more complex than that of other musculoskeletal disorders.

• Physical Therapy Rehabilitation Science
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• v.5 no.1
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• pp.34-39
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• 2016

Objective: Hip abductors play a role in providing stability and movement to the lower limbs. The purpose of this study was to examine the effects of hip abductor fatigue on static balance and gait in the general population. Design: One group pre-test post-test design. Methods: Thirteen university students in their twenties volunteered for the study and had underwent a functional assessment. To induce fatigue, the subjects were instructed to raise their dominant lower extremity up against a load of 50% of 1 repetition maximum while producing hip abduction in a side-lying position. Subjects were instructed to maintain an abduction speed of 30 repetitions per minute to induce fatigue. Muscle fatigue was considered to be established when subjects were unable to perform hip abduction three consecutive times along with the metronome. A post-test of balance and gait was performed immediately in order to prevent fatigue recovery. The center of pressure (COP) distance area was measured using the Zebris FDM-S Multifunction Force measuring plate. Gait performance was analyzed using the GAITRite. Results: The COP distance was increased after fatigue was induced. There was a significant increase in the standard deviation of the medio-lateral and antero-posteror distance (p<0.05). Although there was no significant difference in gait parameters, there was a significant decrease in single support time after fatigue was induced (p<0.05). Conclusions: There was an increase in static balance instability and a significant decrease in single support time during gait due to hip abductor muscle fatigue.