• Proceedings of the ESK Conference
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• 1993.04a
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• pp.100-109
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• 1993

To investigate the work-relatedness of carpal tunnel syndrome of some workers at packing department in a rayon manufacturing company, reseracher studied the symptoms and physical sign related to carpal tunnel syndrome of the workers at packing, ysrning, and washing department. The results are as follows: 1. By the results of ergonomic study, the packing work had the considerable probability to develop the carpal tunnel syndrome. 2. The prevalences of symptoms, physical sign and case by definition were higher in woman workers than in man workers. 3. In female workers, the age-agjusted prevalence rates of symptoms were 11.6/1, 000 in workers at washing department, 111.6/1, 000 in workers at packing department, and 70.1/1, 000 in workers at yarning department. In male workers, the age- adjusted rates of symptoms were 92.1/1, 000 in workers at washing department, 210.1/1, 000 in workers at packing and delivery department, and 0.0/1, 000 in workers at yarning department. 4. In female workers, the age-adjusted prevalence rates of physical signs were 119.5/1, 000 in workers at washing department, 104.4/1, 000 in workers at packing department, and 84.5 in workers at yarning department. In male workers, the age-adjusted rates of physical signs were 65.7/1, 000 in workers at washing department, 59.0/1, 000 in workers at packing and delivery department, and 176.9/1, 000 in workers at yarning department. 5. In female workers, the age- adjusted prevelence rates of carpal tunnel cases by case definition were 123.1/1, 000 in workers at washing department, 1117.2/1, 000 in workers at packing department, and 60.2/1, 000 in workers at yarning department. In male workers, the age-adjusted of cases were 355.9/1, 000 in workers at packing and delivery department, and 0.0/1, 000 in workers at other two departments. 6. The most of female workdrs at washing departmentn had the work history at packing department. 7. We concluded the carpal tunnel syndrome of female workers at packing department were work related.

• Journal of the Ergonomics Society of Korea
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• v.25 no.3
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• pp.17-24
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• 2006

In this paper, we propose a stress analysis on foot by lifting task attitudes. Maximum force and peak pressure were measured on 8 body regions by Pedar system in order to analysis the stress which is affected by task style and angle on foot when Manual Materials Handling task. As for the peak pressure of the whole foot as to the task height during the lifting task, the height from Knuckle to Shoulder was the least in the peak pressure. Also, as for the maximum force and the peak pressure of the whole foot as to the task angle during the lifting task, it could be seen that the more an angle increases, the stress influencing on a foot jumps. As for the maximum force and the peak pressure by foot region as to the task height in case of the lifting task, the height from Knuckle to Shoulder is indicated the smallest value in the maximum force and the peak pressure, thus there is necessary to attain the work design that considered this. Also, as for the maximum force by foot region as to the task angle in case of the lifting task, 0° tasking is indicated to be least, thus there is necessity to be attained the tasking design in a bid to prevent the existence of an angle. The results of this paper are thought to be helpful to the suitable work design, to the prevention of musculoskeletal disorders related to the lower limbs, and to the design of ergonomic safety shoes.

• Journal of the Ergonomics Society of Korea
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• v.32 no.3
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• pp.267-271
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• 2013

Objective: The purpose of this study is to examine the test-retest reliability of paper-pencil test for investigating population stereotype of burner-control linkages of four-stove gas ranges. Background: Much of the research on gas-range stereotype strength has been performed using the paper-pencil test. While the use of the paper-pencil tests has the advantage of collecting data in a large group of subjects against reasonable costs, concerns regarding the reliability of the paper-pencil test has also been stated. Method: Three paper-pencil tests classified by intervals of test-retest were performed, in which eight types of burner-control arrangements were investigated. Sixty eight subjects were test-retested within two weeks, 85 subjects were test-retested within four weeks and 58 subjects were test-retested three times in series with interval of two and four weeks. Results: Chi-square test showed that three intervals of test-retest including two, four and two & four weeks have not statistically significant effect on subjects' responses irrespective of eight types of burner-control linkages dealt with in this study(p>0.10). Concordance rates of subjects' responses ranged between 73.5% and 100.0% for two-week test-retest, between 67.1% and 97.6% for four-week test-retest, and between 65.5% and 100.0% for two- and four-week serial test-retest. The concordance rates were linearly correlated with proportion of subjects' responses for stereotypes of burnercontrol linkages. Conclusion: It is concluded that the paper-pencil tests for investigating gas range relevant stereotypes could reproduce reliable results compared to baseline test within interval of four weeks. Application: The results of this study would be useful as an ergonomic guideline when designing the paper-pencil tests for stereotype relevant studies.

• Journal of the Ergonomics Society of Korea
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• v.32 no.3
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• pp.237-243
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• 2013

Objective: The present study developed an estimation method of boundary zone representative humanoids(hereafter, EBZ method) using descriptive statistics on the design target population. Background: The boundary zone method(hereafter, BZ method) generates representative humanoids at a boundary zone that statistically accommodates a designated percent of the design target population; however, the BZ method has a practical limitation because it requires a large scale anthropometric database on the design target population. Method: The EBZ method developed in the present study consisted of 3 steps. In the first step, the boundary zone of accommodating a designated percent(e.g., 90%) is formed under the assumption of normal distributions for anthropometric sizes. In the second step, cases that fall within the boundary zone are estimated using descriptive statistics(mean, standard deviation, and covariance) on the design target population. In the last step, K-mean cluster analysis is conducted for the cases, and representative humanoids are selected from each of clusters. Results: Evaluation results showed that mean accommodation percent of the EBZ method was 90.9%(range: 90.8~91.1%) which is similar to the target percent(90%). In addition, standard deviation of accommodation percent for 100 repetitions was 0.1%. Lastly, the number of representative humanoids generated by the EBZ method(n = 20) was similar to the BZ method(n = 16). Conclusion: The EBZ method can generate representative humanoids which accommodate a designated percent of the design target population using descriptive statistics. Application: The EBZ method can be utilized in the generation of humanoids for ergonomic design and evaluation of products when the large scale anthropometric database on the design target population is not existed.

• Journal of the Korea Safety Management & Science
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• v.13 no.2
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• pp.83-90
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• 2011

It has been very important to have an exact evaluation for risk factors in order to prevent WMSDs(Work-related Musculoskeletal Disorders). However, most WMSDs evaluation methods have always been some problems of possibilities associated with subjective evaluation. Therefore, this study tried to conduct a sort of usability analysis on three major evaluation methods(OWAS, RULA, REBA). Specifically, major subjects in the study consisted of three parts as follows; comparison of the results between experienced and inexperienced observers, analysis for the consistency of the results in terms of different evaluation times, and analysis for the consistency of the results in terms of different job characteristics(based on the part of the automobile). The results of the study were summarized as follows; 1) There was statistically significant difference of the results by RULA and by REBA between experienced and inexperienced observers. This might be due to the fact that experienced observers have had better ability to detect the important working posture during evaluation. However, the results by OWAS did not give any significantly different results between experienced and inexperienced observers, 2) All three checklists applied by experienced subjects did not show any single result significantly different in terms of different evaluation times. This might have to do with high intra-observer reliability from some of previous studies, 3) The five parts of an automobile were selected as five major jobs with different job characteristics in the automobile industry. Specifically, they were door part, front part(hood, etc.), inside part(dash board, seats, etc.), rear part(trunk etc.), and bottom part. All three methods did not show any significant differences for the results from each observers. Further study on this subject would eventually provide a sophisticated evaluating guidelines for WMSDs regarding determination of observer-specific evaluation, identification of repetitive number of evaluations for stable results for each checklist, determination of job-specific evaluation methods, and so on.

• Physical Therapy Korea
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• v.13 no.1
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• pp.24-31
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• 2006

The purpose of this study was to identify the effect of the hip internal rotation on gluteal and erector spinae muscle electromyographic (EMG) activity during treadmill walking. Eleven healthy subjects were recruited. All subjects performed treadmill walking while maintaining the hip in neutral position (condition 1) and in internal rotation (condition 2). Surface EMG activity was recorded from four muscles (gluteus maximus (GM), gluteus medius (GMED), tensor fascia latae (TFL), and erector spinae (ES)) and the hip internal rotation angle was measured using a three dimensional motion analysis system. The gait cycle was determined with two foot switches, and stance phase was normalized as 100% stance phase (SP) for each condition using the MatLab 7.0 program. The normalized EMG activities according to the hip rotation (neutral or internal rotation) were compared using a paired t-test. During the entire SP of treadmill walking, the EMG activities of GM in condition 1 were significantly greater than in condition 2 (p<.05). The EMG activities of TFL and ES in condition 2 were significantly greater than in condition 1 (p<.05). The EMG activities of the GMED in condition 1 were significantly greater than in condition 1 (p>.05) except for 80~100% SP. Further studies need randomized control trials regarding the effect of hip internal rotation on the hip and lumbar spine muscle activity. Kinetic variables during gait or going up and down stairs are also needed.

• Physical Therapy Korea
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• v.18 no.4
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• pp.34-42
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• 2011

The lumbrical muscles contribute to the intrinsic plus position, that is simultaneous metacarpophalangeal (MCP) flexion and interphalangeal (IP) extension. The strength of the lumbrical muscles is necessary for normal hand function. However, there is no objective and efficient method of strength measurement for the lumbrical muscles. In addition, previous studies have not investigated the measurement of the cross-sectional area (CSA) of the lumbrical muscles using ultrasonography (US) and the relationship between lumbrical muscle strength in the intrinsic plus position and the CSA. Therefore, the purpose of this study was to identify the measurement method of the CSA of the lumbrical muscles using US and to examine the relationship between maximal isometric strength and the CSA of lumbrical muscles. Nine healthy males participated in this study. Maximal isometric strength of the second, third, and fourth lumbrical muscles was assessed using a tensiometer in the intrinsic plus position which isolated MCP flexion and IP extension. The CSA of the lumbrical muscles was measured with an US. The US probe was applied on the palmar aspect of the metacarpal head with a transverse view of the hand in resting position. There was no significant difference between maximal isometric strength of the lumbrical muscles, but the fourth lumbrical muscle was stronger than the others. The CSA of the lumbrical muscles was significantly different and the fourth lumbrical muscle was significantly larger than the second lumbrical muscle. There was moderate to good correlation between maximal isometric strength and the CSA of the lumbrical muscles. Therefore, we conclude that maximal isometric strength of the lumbrical muscles was positively correlated to the CSA of the lumbrical muscle in each finger, while the measurement of the CSA of the lumbrical muscles, using US protocol in this study, was useful for measuring the CSA of the lumbrical muscles.

• Physical Therapy Korea
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• v.18 no.4
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• pp.19-25
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• 2011

The aims of this study were to investigate the correlation between the electromyographic (EMG) activity of the abductor hallucis (AbdH) and the amount of pressure measured by a pinch gauge (PG), and to compare the EMG activity of AbdH and the pressure measured by the PG during short foot (SF) exercise in subjects with pes planus and in subjects with a neutral foot alignment. Fourteen subjects were recruited for this study (pes planus group=7; neutral foot alignment group=7). A surface EMG was used to collect AbdH activity, and a PG was positioned under the first metatarsophalangeal joint to measure the pressure produced by the first metatarsal head during the SF exercise. The AbdH activity and the pressure measured by the PG showed a positive good correlation (r=.80, p<.05). The EMG activity of the AbdH and the pressure measured by the PG were significantly lower for subjects with pes planus than for subjects with a neutral foot alignment (p<.05). Based on these findings, the PG can be recommended as an effective instrument for evaluating the performance of the AbdH. It may also be beneficial for monitoring how well the SF exercise is performed, and for providing visual feedback to patients with pes planus during SF exercise in a clinical setting.

• Physical Therapy Korea
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• v.18 no.4
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• pp.1-10
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• 2011

This study compared the stability of the cervical spine according to the presence of neck pain and deep neck flexor performance. Thirty subjects with neck pain, and thirty subjects without neck pain were recruited for this study. The Cranio-cervical flexion (CCF) test was applied using a pressure biofeedback unit to classify the subjects into four subgroups; no cervical pain and good deep neck flexor performance (NG group), no cervical pain and poor deep neck flexor performance (NP group), cervical pain and good deep neck flexor performance (PG group), and cervical pain and poor deep neck flexor performance (PP group). The head sway angle was measured using a three-dimensional motion analysis system. A 3-kg weight was used for external perturbation with the subject sitting in a chair in the resting and erect head positions with voluntary contraction of the deep neck flexors. A one-way analysis of variance (ANOVA) was performed with a Bonferroni post hoc test. The deep neck flexor performance differed significantly among the four groups (p<.05). The NG group had significantly greater deep neck flexor performance than NP and PP groups. The stability of the cervical spine also differed significantly among the four groups in the resting head position (p<.05). The head sway angle was significantly smaller in NG group as compared with the other groups. The PP group had the greatest head sway angle in the resting head position. However, there was no significant difference in the stability of the cervical spine among the groups in the erect head position with voluntary contraction of deep neck flexors (p=.57). The results of this study suggest that the deep neck flexor performance is important for maintaining the stability of cervical spine from external perturbation.

• Physical Therapy Korea
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• v.16 no.3
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• pp.42-49
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• 2009

This study examined the vastus medialis oblique (VMO) and the vastus lateralis (VL) onset time differences (OTD) during quadriceps contraction in different hip positions. Twelve healthy subjects were recruited (four men, eight women). Surface EMG activities of the VMO and VL were measured during a quadriceps strengthening exercise in a long sitting condition and in a sitting at a chair with feet hanging condition. For each condition, subjects were tested in two hip positions (neutral and adduction). The OTD between the two muscles was calculated for each condition, by subtracting the onset time of the VL from the VMO. Therefore, the negative value of OTD represent earlier EMG onset of the VMO compared to the VL. The OTD was not significantly different between the hip neutral and the hip adduction position in the long sitting condition (p=.064). However, the OTD was significantly different between the hip neutral position ($15.83{\pm}109.51$ ms) and hip adduction position ($-5.58{\pm}121.08$ ms) during the sitting at a chair with feet hanging condition (p=.047). The negative OTD value in the hip adduction condition during quadriceps strengthening exercises is the result of earlier onset of the VMO than VL. Therefore, quadriceps contraction in the hip adduction position can prevent the risk of patella lateral tracking. We expect that quadriceps strengthening exercise in the hip adduction position will be a safe way to prevent patellofemoral pain syndrome resulting from abnormal patella lateral tracking.