• 대한인간공학회지
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• 제25권3호
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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.

• Safety and Health at Work
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• 제4권2호
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• pp.105-110
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• 2013

Background: To determine the influence of lifting speed and type on peak and cumulative back compressive force (BCF) and shoulder moment (SM) loads during symmetric lifting. Another aim of the study was to compare static and dynamic lifting models. Methods: Ten male participants performed a floor-to-shoulder, floor-to-waist, and waist-to-shoulder lift at three different speeds [slow (0.34 m/s), medium (0.44 m/s), and fast (0.64 m/s)], and with two different loads [light (2.25 kg) and heavy (9 kg)]. Two-dimensional kinematics and kinetics were determined. A three-way repeated measures analysis of variance was used to calculate peak and cumulative loading of BCF and SM for light and heavy loads. Results: Peak BCF was significantly different between slow and fast lifting speeds (p < 0.001), with a mean difference of 20% between fast and slow lifts. The cumulative loading of BCF and SM was significantly different between fast and slow lifting speeds (p < 0.001), with mean differences ${\geq}80%$. Conclusion: Based on peak values, BCF is highest for fast speeds, but the BCF cumulative loading is highest for slow speeds, with the largest difference between fast and slow lifts. This may imply that a slow lifting speed is at least as hazardous as a fast lifting speed. It is important to consider the duration of lift when determining risks for back and shoulder injuries due to lifting and that peak values alone are likely not sufficient.

• 한국전문물리치료학회지
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• 제5권1호
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• pp.30-43
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• 1998

The purposes of this study were to examine the effect of two different pelvic alignments and the Valsalva maneuver on electromyographic (EMG) activity of the erector spinae during squat lifting and lowering, and to find an efficient method for squat lifting and lowering. Twenty hea1thy men in their twenties lifted and lowered loads using four different methods: 1) anterior pelvic tilt position with the Valsalva maneuver, 2) anterior pelvic tilt position without the Valsalva maneuver, 3) posterior pelvic tilt with the Valsalva maneuver, 4) posterior pelvic tilt without the Valsalva maneuver. The EMG activity of erector spinae was recorded during both lifting and lowering with each method. The EMG activity of each individual was normalized to EMG activity produced by muscle during maximal voluntary contraction. Two-way analysis of variance for repeated measures ($2{\times}2$) was used to analyze the effect of the two factors: 1) pelvic tilt position (anterior pelvic tilt, posterior pelvic tilt), 2) the Valsalva maneuver (with and without). Analysis was performed separately for the lifting and lowering. The results were as follows: 1) EMG activity of erector spinae was greater when the pelvis was tilted anteriorly than when the pelvis was tilted posteriorly during squat lifting and squat lowering. 2) There was no difference between EMG activity of erector spinae with the Valsalva maneuver and EMG activity of erector spinae without the Valsalva maneuver during squat lifting and squat lowering. These results suggest that the greater EMG activity of erector spinae with an anterior pelvic tilt position during squat lifting and squat lowering may ensure optimal muscular support for the spine while handling loads, but the Valsalva maneuver may have less effect on erector spinae.

• 한국산업보건학회지
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• 제19권1호
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• pp.25-29
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• 2009

The purpose of this study was to investigate the effect of two different lifting posture on the plantar foot pressure, force and COP(center of pressure) trajectory path during object lifting. Fourteen healthy adults who had no musculoskeletal disorders were instructed to lift with two postures(stoop and squat) and two object weights(empty box and 10 kg box). Plantar foot pressures, forces and COP trajectory path were recorded by the F-mat system(Tekscan, Boston, USA) during object lifting with barefoot. Plantar foot surface was defined as seven regions for pressure measurement; two toe regions, three forefoot regions, one midfoot region and one heel region. Paired t-test was used to compare the outcomes of peak pressure and maximum force with different two lifting postures and two object weights. Plantar peak pressure and maximum force under hallux was significantly greater in squat posture than stoop posture during the two different boxes lifting(p<.05). During the empty box lifting, maximum force under lessor toes was significantly less and plantar peak pressure under second metatarsal region was significantly greater in squat than stoop(p<.05). Maximum force under heel was significantly less in squat than stoop posture during 10kg box lifting(p<.05). Finally, COP trajectory path was significantly greater in squat than stoop(p<.05). These findings confirm that there are significantly change in the structure and function of the foot during the object lifting with different posture. Future studies should focus on the contribution of both structural and functional change to the development of common foot problems in adults.

• 한국안전학회지
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• 제12권4호
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• pp.209-213
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• 1997

Manual lifting techniques are commonly defined in terms of the postures adopted at the start of the lift. Quantitative definition is problematic, however, because the absolute joint angles adopted to lift an object are influenced by task parameters, such as the initial height of the load. The main objective of this study is to investigate the grip strength of the both hands at the initial lifting points. The survey is conducted by measuring the compression force, anthropometric data and grip strength at the lifting postures for the subjects(n=50) who is assigned to their job as usual. The experiment is peformed at the four lifting postures which involving the combination of two horizontal factors(H1 : 35 cm, H2 : 55 cm) and two vertical factors(V1 : 20~80 cm, V2 : 47~102 cm). The analysis result of lifting posture indicated that each H1-V1, H2-V1 combinations are about 60$^{\circ}$ and each H1-V2, H2-V2 combinations are about $30^{\circ}$. There are significant differences on grip strength between $60^{\circ}$ and $30^{\circ}$ stooped posture. The results of this study can be provided a method defining lifting postures at the minimum grip strength. Also, it is eliminated a hazard of the injuries which are cumulative trauma disorders(CTDs) and back pain, increased a productivity and improved a welfare of workers.

• 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.

• 대한산업공학회지
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• 제11권2호
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• pp.87-99
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• 1985

The purpose of this study is to analyze the changes in centers-of-gravity (COG), acceleration and body posture and their associated effects both on EMG and on the maximum capability of weight lifting during Clean & Jerk and Snatch motions. Displacement, velocity, acceleration of joints were obtained from film analysis. Also levels of exertions on 11 major muscle groups were obtained from EMG analysis during a lifting cycle. The EMG data were measured from Telemetry System which is useful in field experiments. Magnitude and direction of force, change in center-of-gravity were extracted from COG data which were measured from force platform. The results of this study can be to be useful both to coaches and to athletes in weight-lifting.

• Journal of Ship and Ocean Technology
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• 제7권3호
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• pp.34-55
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• 2003

Explicit Kutta condition approximation, proved useful in existing time-domain solver of the unsteady propeller problem, requires a specified functional behavior of the vorticity in space near the trailing edge. In this paper, the strength of the discrete vortices is controlled to have a specified behavior in space in the frequency domain approach. A new formulation is introduced and is implemented for analysis of a lifting surface of a rectangular planform. Sample computations carried out according to the new formulation compares well with that of existing unsteady lifting problem in the time domain.

• 융복합기술연구소 논문집
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• 제4권1호
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• pp.37-41
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• 2014

For the analysis of lifting surface at high angle of attack, a Nonlinear Vortex Lattice Method(NLVLM) was used. The NLVLM is intented to compute the interactions between lifting surfaces and separated vertical flow. The lifting surfaces are represented by a lattice of discrete vortex rings. And wakes are represented by families of non-lintersecting, semi-infinite vortex line segments. The image method also used to analyze the ground effect. It is found that vortex lines separated from lifting surfaces represent the separated flows successfully. Although the present method is applied for the rectangular wing and delta wing, extensions can be possible for the arbitrary lifting surfaces. The Present results show good agreement with experimental data.

• 한국건설관리학회논문집
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• 제14권4호
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• pp.73-83
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• 2013

최근 국내 외 대도시를 중심으로, 글로벌 경제 위기와 부동산 경기 침체로 중단되거나 연기되었던 초고층 프로젝트들이 재개되고 있으며, 이를 수주하기 위한 건설사들의 경쟁은 전보다 더욱 치열해지고 있다. 국내 건설사들이 초고층 건축 분야에서 경쟁력을 높이기 위해서는, 전체 프로젝트의 근간이 되는 중요한 요소인 양중계획의 체계적인 리스크 관리가 반드시 수반되어야 하지만, 여전히 개인적 경험에 의존하여 작성 된, 양중계획의 오류로 인한, 현장 전체의 공기 지연 및 원가 관리 실패의 문제가 빈번하게 발생하고 있다. 따라서 본 연구에서는, 양중계획의 정확성을 높이기 위한 방안으로, 현행 양중계획 체계의 문제점을 분석하고, 계획 요소에 따라 실패 유형을 도출하였으며, 각 실패 유형이 전체 프로젝트의 공정, 원가, 안전관리에 미치는 영향도를 분석하였다. 또한 양중 장비별 세부 리스크 요인을 분석하고, 이를 바탕으로 FMEA 기법을 적용하여 초고층 프로젝트 양중계획의 핵심 리스크 요인을 도출하였다.