Occupational Ergonomics - Volume 7, issue 4

Authors: Gedliczka, Adam | Konarska, Maria | Hamiga, Krzysztof | Machynia, Zbigniew | Starzyńska, Krystyna | Mircea, Jowita | Noworol, Czesław

Article Type: Research Article

Abstract: Forced postures are regarded as related to the location of a technical structure's touch points. The aim of this research study was to interpret the basic biomechanical criteria of the EN 1005-4 standard (also ISO/DIS 11226), defining standing posture categories as parameters of the corresponding arm reach envelopes. This form of data presentation makes direct application of these criteria possible in the design and evaluation of a technical structure. Forced static postures were simulated according to angle ranges of the standard for trunk bending and upper arm elevation. Arm reach of representatives of the Polish population was measured with a …model consisting of modular elements movable perpendicularly to the frontal plane. The results formulated in the Cartesian system of co-ordinates were developed with Mechanical Desktop software and presented as spatial arm reach envelope models, and graphically, too. In practice it was possible to compare the location of touch points with reach envelopes to assess just the technical structure according to the assumed working posture categories as acceptable, conditionally acceptable or unacceptable. Show more

Keywords: Static forced posture categories, spatial models of arm reach, assessments method

DOI: 10.3233/OER-2007-7401

Citation: Occupational Ergonomics, vol. 7, no. 4, pp. 219-231, 2007

Authors: Muzammil, Mohammad | Khan, Abid Ali | Hasan, Faisal

Article Type: Research Article

Abstract: The present study was designed to investigate the effect of noise and heat stress on operators of various age groups performing die casting operation at varying exposure durations. The independent variables selected were age of operator (20–25, 25–30 and 30–35 years), equivalent levels of noise (90, 95 and 100 dB(A)), heat stress (35, 40 and 45°C wet bulb globe temperature) and exposure duration (5, 10 and 15 minutes) while the dependent variable was heart rate measured with the help of pulse-oximeter. The results of the study showed that the main effects of heat stress, equivalent noise level, age group and …the interaction between levels of equivalent noise and exposure duration were all had a statistically significant effect on operators performing the task. The three way interaction of age group, subject and equivalent noise level was also observed to be statistically significant. Show more

Keywords: Equivalent noise, heat stress, exposure duration, heart rate

DOI: 10.3233/OER-2007-7402

Citation: Occupational Ergonomics, vol. 7, no. 4, pp. 233-245, 2007

Authors: Diaz-Zeledon, Marianela | Lin, Chih-Long | Landau, Kurt

Article Type: Research Article

Abstract: The objective of this study is to investigate the effect of the variations of an objects' instability, on the upper body and trunk locomotion system during self-paced, 3D, and reaching and transport movements performed in a seated position. Unstable objects can be found in many industrial sectors, such as chemical industries or service areas. Due to the deficit in methods of their manipulations and investigations of the related effects has motivated the present study. 30 subjects (15 male, 15 female) participated in this experiment. The physical human responses were measured using (a) self-paced Hand Motion Time, (b) Range of Motion …of the trunk, shoulder, and elbow, (c) muscular strain of selected muscle groups in the shoulder, arm, and trunk. The mental workload is measured by subjective assessment, of the unstable moved object. The results of the statistical tests prove that there is an effect of the liquid level and target position on the physical and mental level of the locomotion system. Direction of movement (motion-phase) presents a significant influence on the Range of Motion, the muscular activity and the Hand Motion Time. These results can be applied to evaluate, and develop products for workplaces, where the reduction of musculoskeletal injuries plays an important role. Show more

Keywords: Motion-analysis, unstable objects, workplace design, muscular strain, hand motion time, range of motion

DOI: 10.3233/OER-2007-7403

Citation: Occupational Ergonomics, vol. 7, no. 4, pp. 247-263, 2007

Authors: Duncan, Carolyn A. | MacKinnon, Scott N. | Albert, Wayne J. | Antle, David M. | Matthews, Julie

Article Type: Research Article

Abstract: The purpose of this study was to examine the effect of simulated vessel motions and load stabilities on thoracolumbar kinematics and foot centre of pressures (CoP) kinematics during the execution of common manual material handling (MMH) tasks. Nine male subjects completed a standing, holding and lifting task in three different simulator motion conditions (no motion, pitch and roll) while handling both a stable and unstable load (15 kg). Stability of load did not affect thoracolumbar kinematics, CoP or occurrence of motion induced interruptions (MIIs) while lifting or holding a load in any of the motion environments. Although no differences in …thoracolumbar kinematics and CoP during the dynamic lifting task between baseline and either pitch or roll conditions were found, total anterior-posterior CoP displacements and thoracolumbar velocities were greater during motion conditions for stationary holding and standing tasks. MIIs occurred more often during the standing task than the lifting tasks. These results suggest that the rate of MII occurrence may be a function of the dynamic nature of the MMH task being performed. Tasks which restrain the movement of the individual may prevent the body from making adequate adaptations when stability is disturbed, increasing the likelihood for change-in-support strategies, potential for loss of balance and resultant injury. Show more

Keywords: Postural stability, thoracolumbar kinematics, centre of pressure, motion induced interruptions

DOI: 10.3233/OER-2007-7404

Citation: Occupational Ergonomics, vol. 7, no. 4, pp. 265-274, 2007

Authors: Larsman, Pernilla | Pousette, Anders | Hanse, Jan Johansson

Article Type: Research Article

Abstract: The aim was to test a structural model of the relations between psychological and mechanical workload and musculoskeletal neck/shoulder symptoms. This two-wave longitudinal cohort study was based on a questionnaire survey among Swedish female child-care workers (n=789). Two models were tested using structural equation modelling, one containing only those participants considered symptom free at baseline, thus focusing on symptom development, and one containing all participants irrespective of their baseline musculoskeletal status. The results indicate that psychological workload was related to the development of neck/shoulder symptoms, and thus highlight the importance of addressing psychosocial work environment factors in organization design and …workplace interventions. However, psychological workload was not related to symptoms (when controlling for baseline mechanical workload and symptoms) in the model not distinguishing between different symptoms processes. These findings point to the importance of distinguishing between different processes such as development, maintenance and recovery from symptoms in studies of workplace factors and musculoskeletal symptoms. Mechanical workload was not related to neck/shoulder symptoms, when controlling for baseline psychological workload and symptoms, in any of the models tested. No interaction effect was found for psychological and mechanical workload on neck/shoulder symptoms. Show more

Keywords: Child-care work, psychological workload, mechanical workload, musculoskeletal symptoms, structural equation modelling, longitudinal analysis

DOI: 10.3233/OER-2007-7405

Citation: Occupational Ergonomics, vol. 7, no. 4, pp. 275-287, 2007