• Title, Summary, Keyword: External Load

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Psychophysical Load for Females Depending on Arm Posture, Repetition of Wrist Motion and External Load (여성의 팔 자세, 손목 동작 반복과 외부 부하에 따른 심물리학적 부하)

  • Kee, Do-Hyung
    • Journal of the Korean Society of Safety
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    • v.21 no.3
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    • pp.122-126
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    • 2006
  • This study investigated effect of arm posture, wrist motion repetition and external load on perceived discomfort through an experiment. Eleven female college students participated in the experiment, where shoulder, elbow and wrist motion, wrist motion repetition, and external load were used as independent variables. The results showed that only external load had a significant effect on perceived discomfort. The perceived discomfort linearly increased with external load. Based on the results of this and the previous study for males, it was concluded that effect of external load on perceived discomfort was larger than that of other posture and motion repetition related variables. This implies that effect of external load is the most important factor considered in the first place when assessing postural load.

Psychophysical Stress of Arm Motions at Varying External Load and Repetition (외부 부하와 반복에 따른 팔 동작의 심물리학적 자세 부하)

  • Kee, Do-Hyung
    • IE interfaces
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    • v.17 no.2
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    • pp.218-225
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    • 2004
  • This study aims to investigate effect of external load and motion repetitiveness on perceived discomfort. An experiment was performed for measuring discomfort scores at varying conditions, in which external load, motion repetitiveness and arm posture were employed as experimental variables. The arm posture was controlled by shoulder flexion and abduction, and by elbow flexion. Fifteen healthy college-age students without history of musculoskeletal disorders voluntarily participated in the experiment. The results showed that the effect of external load, motion repetitiveness and shoulder posture on discomfort were statistically significant, but that elbow posture did not significantly affect discomfort ratings. The effect of external load was much larger than that of any other variables, and that of repetitiveness was second only to external load. Discomfort scores significantly increased linearly as the levels of external load and motion repetitiveness increased. This implies that although they were not fully reflected in the existing posture classification scheme such as OWAS, RULA, etc., the effect of external load and motion repetitiveness should be taken into consideration for precisely quantifying work load in industry. Based on regression analysis, equivalent values of external load and motion repetitiveness in terms of discomfort scores were provided, which would be useful for better understanding the degree of their effect on work load.

Investigation on Perceived Discomfort Depending on External Load, Upper Limb Postures and their Duration (외부 부하, 상지 자세와 지속 시간에 따른 지각 불편도)

  • Kee, Dohyung
    • Journal of Korean Institute of Industrial Engineers
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    • v.30 no.2
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    • pp.76-83
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    • 2004
  • This study aimed to empirically investigate perceived discomfort depending upon external load, upper limb postures and their holding time. Discomfort was obtained through an experiment, in which external load, wrist flexion/extension, elbow flexion, shoulder flexion and adduction/abduction were used as experimental variables. The subjects were instructed to hold given postures for 60s and to rate their subjective discomfort scores at 5s, 20s, 40s and 60s by using the free modulus method of magnitude estimation. The results showed that while only external load and elbow flexion were statistically significant at the holding time of 5s at ${\alpha}=0.05$ or 0.10, external load and upper limb postures excluding shoulder adduction/abduction significantly affected discomfort ratings at 20s, 40s and 60s at ${\alpha}=0.01$ or 0.05. Discomfort scores were also significantly different between four posture holding times at ${\alpha}=0.01$. The effects of external load and holding time were much larger than those of upper limb postures. Based on the results of this study, it is recommended that external load and holding time as well as working postures betaken into consideration to precisely quantify postural load in industry.

Psychophysical Stess Depending on Repetition of Wrist Motion and External Load (손목 동작의 반복과 외부 부하에 따른 심물리학적 부하)

  • Kee, Do-Hyung
    • Journal of the Korean Society of Safety
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    • v.19 no.4
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    • pp.123-128
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    • 2004
  • This study investigated effect of arm posture, repetition of wrist motion and external load on perceived discomfort. The arm postures were controlled by shoulder flexion, elbow flexion, and ist motions such as flexion, extension, radial deviation and ulnar deviation. An experiment was conducted to measure discomfort scores for experimental treatments using the magnitude estimation, in which the L16 orthogonal array was adopted for reducing the size of experiment. The results showed that while the effect of the shoulder flexion, repetition of wrist motion and external load was statistically significant at $\alpha=0.05$or 0.10, that of the elbow and wrist motions was not. Discomfor ratings increased linearly as levels of wrist repetition and external load increased. This implies that the existing posture classification schemes such as OWAS, RULA, which do not properly consider effect of motion repetition and external load, may underestimate postural load. Based on the regression equation for wrist repetition and external load, isocomfort region indicating the region within which discomfort scores were expected to be the same was proposed. It is recommended that when assessing risk of postures or developing new posture classification schemes, motion repetition and external load as well as posture itself be fully taken into consideration for precisely evaluating postural stress.

Effects of External Load and Upper Extremity Postures on Perceived Discomfort (지각 불편도에 대한 외부 부하, 상지 자세의 영향)

  • Kee, Do-Hyung
    • Journal of the Korean Society of Safety
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    • v.17 no.4
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    • pp.178-183
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    • 2002
  • The purpose of this study was to quantitatively investigate the effects of external load upper extremity posture on perceived discomfort. An experiment was conducted for measuring discomfort scores depending upon external loads and upper extremity postures, in which the free modules and numeric estimate method of the magnitude estimation was adopted as a tool for obtaining discomfort ratings. The upper extremity postures were controlled by wrist flexion/extension, elbow foexion, shoulder flexion, and shoulder adduction/abduction. The results showed that all experimental variables except shoulder adduction/abduction were significant at ${\alpha}$=0.01 or 0.05. The effect of external load was very much larger than that of upper extremity postures. Therefore, it is recommended that a new posture classification scheme taking effect of external load to into consideration be developed for quantifying postural load.

Development of a Posture Classification Scheme Reflecting the Effects of External Load and Motion Repetition (외부 부하, 동작 반복 효과가 반영된 자세 분류 체계의 개발)

  • Kee, Do-Hyung
    • Journal of the Ergonomics Society of Korea
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    • v.26 no.1
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    • pp.39-46
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    • 2007
  • The purpose of this study was to develop a comprehensive posture classification scheme considering the effects of external load and motion repetition as well as those of working posture. The scheme was developed based on a series of existing empirical studies dealing with postural classification scheme, effects of external load and motion repetition. Ranges of joint motions, external load and motion repetition were divided into the groups with the same degree of discomforts. Each group was assigned a numerical relative discomfort score of code on the basis of discomfort values for the neutral position of elbow flexion. The criteria for evaluating stress of working postures were proposed based on the four distinct action categories, in order to enable practitioners to apply appropriate corrective actions. The proposed scheme was compared with OWAS, RULA and REBA. The comparison revealed that while the proposed scheme and RULA showed similar results for the working postures with light external load and non-repetitive postures, the former overestimated postural load for postures with moderate or heavy external load and repetitive postures than the latter.

Effect of External Load on Shoulder Joint Active Relocation Using 3D Motion Capture System: A Pilot Study (외부 하중이 어깨관절의 능동적 재위치 검사 결과에 미치는 영향: 3차원 동작 분석 시스템을 이용한 예비연구)

  • Hwang, Jisun;Hwang, Seonhong
    • Physical Therapy Korea
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    • v.25 no.2
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    • pp.71-77
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    • 2018
  • Background: There are insufficient objective or quantitative evidence for the better intervention to improve proprioception particularly for the application of external load. There are conflicting opinions whether the external load is effective for proprioception improvement or not. Objects: The purpose of this study was to investigate effects of external load on proprioception of shoulder joint quantitatively using 3D motion capture system. Methods: Nine healthy adults joined for this study. They were asked to perform scapular plane abduction motion with attaching reflective markers on the trunk and upper limb. The 3D positions of finger marker, while they performed the same task with and without external load, were recorded and analyzed. Results: All participants showed decreased variable errors in the vertical direction when the external load was applied (p<.02). Even though other directions (y, z) and absolute errors increased, they did not have statistical significances. Conclusion: Based on this study results, the external load application would be effective for shoulder joint position sense improvement.

Perceived Discomfort of Upper Body Postures with Varying External Loads (상체의 자세 변화에 따른 외부부하에 대한 불편도 영향 평가)

  • Choe, Dong-Sik;Park, Seong-Jun;Jeong, Ui-Seung;Choe, Jae-Ho
    • Journal of the Ergonomics Society of Korea
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    • v.23 no.4
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    • pp.45-56
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    • 2004
  • The purpose of this study is to evaluate perceived discomfort of working postures in terms of upper body (back, shoulder, and elbow) flexions when an external load varies. Eighteen subjects participated in an experiment of appraising perceived discomfort of varying upper body postures with three levels of external loads given. The ANOVA results showed that the perceived discomfort of upper body postures was significantly affected by the external load. It was also apparent that the interactions between external load and upper body posture were significant (p< 0.001). The result implies that a new posture classification scheme for workload assessment methods may be in need to reflect such interactions between external load and upper body posture. In order to support the statement, a regression model of perceived discomfort of upper body postures obtained from the experiment was developed and compared to that of perceived discomfort of seven work-related postures found in automobile assembly operations. The correlation coefficient between predicted and actual values of perceived discomfort was about 0.96. It is expected that the result help to properly estimate the body stress resluting from worker's postures and external loads and can be used as a valuable design guideline on preventing work-related musculoskeletal diseases in industry.

The Effect of Shoulder and Elbow Postures with External Loads on the Perceived Discomfort (어깨와 팔꿈치의 조합자세 및 외부부하가 지각불편도에 미치는 영향)

  • Kim, Dong-Jin;Na, Seok-Hee;Park, Guk-Mu
    • Journal of the Ergonomics Society of Korea
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    • v.25 no.4
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    • pp.145-151
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    • 2006
  • The objective of this study is to investigate the perceived discomfort for postures combined with shoulder flexion/extension and elbow flexion, and external load. 12 healthy male undergraduate and graduate students participated in this experiment. Experimental variables were the shoulder flexion/extension angle(-20°, 0°, 45°, 90°, 135°), the elbow flexion angle (0°, 45°, 120°), and the external load(0, 1.5Kg, 3Kg) as independent variables and a whole body perceived discomfort using Borg's CR10 as a dependent variable. The subjects maintained the given posture for 60 seconds and then rated the perceived discomfort. The ANOVA results showed that all main factors and two-way interactions were statistically significant at α=0.05. As a result of regression analysis to examine the effect of external load on the perceived discomfort, the perceived discomfort linearly increased as the level of external load increased. Then, the effect of external load on the perceived discomfort was quantitatively classified into three levels based on the result of regression analysis.

Experimental and theoretical studies on SHS column connection with external stiffening ring under static tension load

  • Rong, Bin;You, Guangchao;Zhang, Ruoyu;Ma, Xu;Quan, Xinxin
    • Steel and Composite Structures
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    • v.28 no.2
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    • pp.167-177
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    • 2018
  • In order to investigate mechanical properties in the core area of Square Hollow Section(SHS) column connection with external stiffening ring, four specimens were tested under the static tension load. The failure modes, load-displacement curves and strain distribution were analyzed to study the mechanical properties and the load transfer mechanism of the core area of connections. The connections behave good ductility and load-bearing capacity under the static tension load. Parametric analysis was also conducted, in which the thickness of steel tube, extended width and thickness of the stiffening ring were considered as the parameters to investigate the effects on mechanical properties of the connections. Based on the experimental results, an analytical method for the bearing capacity of connection with external stiffening ring under the static tension load was proposed. The theoretical results and the experimental results are in good agreement, which indicates that the theoretical calculation method of the bearing capacity is advisable.