Occupational Ergonomics - Volume 11, issue 4

Authors: Matsangas, Panagiotis | McCauley, Michael E.

Article Type: Research Article

Abstract: Background: BACKGROUND: Although humans use their lower limbs to compensate when postural equilibrium is affected by external motion perturbations, very little is known about how upper limbs (UL) are used. Such an investigation may provide useful insight into how motion affects manual tasks. Objective: To identify the compensatory postural strategies in which UL are involved and to investigate the association between UL movements, lateral motion perturbations, and motion induced interruptions (MII). Methods: Twenty healthy individuals maintained a quiet stance for one hour on a motion platform. Motion stimuli included lateral perturbations in Sway-only and …Sway+Pitch motion conditions. A kinematic analysis of the video recordings was conducted. Results: Humans make compensatory movements with their UL when lateral motion perturbations challenge their postural equilibrium. Arm elevation is associated with the lateral linear acceleration (sway), the occurrence and the type of MIIs. We focused on the "both arms" strategy because it has an increased potential for interfering with manual tasks compared to single upper limb movements. When individuals take a step to sustain their balance, they use the both hands strategy more often. However, more than 70% of both arms strategy instances occurred in the absence of an MII. Conclusions: Manual task interruptions induced by environmental motion may occur even before or without an MII. The limits of the operational envelope of reduced manual performance should be reconsidered and adopted in lieu of the existing rigid-body model. Show more

Keywords: Motion induced interruptions, upper limbs movements, postural equilibrium, ataxia, motion compensation strategies

DOI: 10.3233/OER-140214

Citation: Occupational Ergonomics, vol. 11, no. 4, pp. 123-136, 2013

Authors: Moore, Christopher W. | Nimbarte, Ashish D. | Rajulu, Sudhakar | Ning, Xiaopeng | Guffey, Steve E.

Article Type: Research Article

Abstract: Background: Little is known about ingress/egress requirements and forward reach for workstations with horizontal seats. This research explored differences between ingress/egress kinematics and reach due to seat orientation. Methods: 10 participants performed ingress/egress tasks using three seat orientations (horizontal with 90° and 120° seat angles, and vertical with 90° seat angle) and planar reach tasks in three anatomical planes using horizontal and vertical seats with 90° seat angle. An optical motion capture system was used to record kinematic data. Marker data was processed and modeled to estimate peak joint angles and ranges of motion of several body …joints. For reach tasks, marker data of the clavicle and finger were used to plot reach capacity. Results: Ingress/egress joint kinematics differed greatly between horizontal and vertical seats, while few differences existed between the horizontal seat orientations. Peak angles and ranges of motion during ingress/egress of the horizontal seats were significantly higher than the vertical seats, often by a factor of 3–4. The direction of motion affected several peak angles and ranges of motion, but to a lesser extent than seat orientation. Reach was unaffected by seat orientation. Conclusion: This study's findings suggest that ingress/egress of horizontal seats is more stressful for the body, especially the shoulders and lower back, than regular upright seats. Show more

Keywords: Ingress, egress, recumbent seats, kinematics, reach envelope

DOI: 10.3233/OER-140213

Citation: Occupational Ergonomics, vol. 11, no. 4, pp. 137-151, 2013

Authors: Smith, Deanne M. | McAuliffe, James | Johnson, Michel J. | Button, Duane C. | Behm, David G.

Article Type: Research Article

Abstract: Background: Inverted positions may arise with emergencies, work or recreational activities. Vigilance which can involve cognition, attention, and decision making is required for activities of daily living, in addition to the avoidance and escape from life threatening situations. Objective: The purpose of this study was to evaluate the effects of an inverted posture on vigilance, heart rate and blood pressure. Methods: Heart rate (HR) and blood pressure (BP), vigilance tasks (Tower of London (ToL), Selective Attention and Response Competition (SARC), Attention Networks Test (ANT)), anxiety and reaction time were assessed with 8 male subjects in an …initial seated upright position, followed an inverted posture and returning to an upright position. Results: TOL was 63.4% and 40.7% slower and SARC was 10.4% and 11.7% slower during the inverted condition compared to the pre- and post-inversion upright assessments (p<0.01). There were no significant changes in ANT. Systolic BP (p<0.0001), diastolic BP (p=0.03), and HR (p<0.01) decreased during inversion, whereas anxiety scores increased 25% and 51% compared to pre- and post-inversion upright conditions. Conclusions: Under inverted conditions, vigilance task capabilities and reaction time were significantly hampered. These decrements could substantially impact responses to emergency situations. Show more

Keywords: Inverted posture, heart rate, blood pressure, attention, anxiety

DOI: 10.3233/OER-140215

Citation: Occupational Ergonomics, vol. 11, no. 4, pp. 153-163, 2013

Authors: Silvestri, Giacomo | Schinkel-Ivy, Alison | Drake, Janessa D.M.

Article Type: Research Article

Abstract: Background: Assessment of trunk muscle co-contraction can provide insight into the behaviour of the trunk musculature, as co-contraction differs between healthy participants and those with low back pain/injury. To date, co-contraction of the trunk musculature has been examined predominately during single-plane and maximal range-of-motion movement tasks. Objective: To assess differences in co-contraction patterns of the trunk musculature as a function of movement task (maximal and combined, mid-range trunk movement tasks) and phase of the movement task. Methods: Thirteen asymptomatic males performed a series of maximal trunk range-of-motion tasks, as well as movement tasks with various combinations …of lumbar and thoracic movements ('combined' movement tasks), in both sitting and standing. Co-contraction between all possible pairings of six bilateral muscles (66 in total) was determined and compared between movement tasks and phase of movement. Results: Twisting and combined movement tasks produced greater co-contraction when moving into and/or holding the position, while uncontrolled flexion movement tasks produced the greatest co-contraction when returning to a neutral upright position. Conclusions: Combined movement tasks and tasks involving twisting required greater co-contraction to actively maintain the positions, providing insight into potential mechanisms of injury if the positions were adopted with high repetition or long duration. These findings are applicable to injury prevention, job and workstation design, rehabilitation practices, and return-to-work protocols. Show more

Keywords: Trunk muscle co-contraction, lumbar spine, thoracic spine, complex motion

DOI: 10.3233/OER-140216

Citation: Occupational Ergonomics, vol. 11, no. 4, pp. 165-176, 2013

Authors: Chan, Albert P.C. | Yang, Yang | Wong, Francis K.W. | Yam, Michael C.H.

Article Type: Research Article

Abstract: Background: Construction workers in Hong Kong face high health risks of heat stress, solar ultraviolet radiation, and hazardous substances. A suitable work wear can lower exposure to these hazards, but the actual dressing behavior of construction workers remains unknown. Objective: This study examines the current dressing patterns of construction workers and evaluates their limitations. Methods: The dressing patterns of construction workers were investigated through unconcealed videotaped observation and questionnaire survey to enhance the reliability and validity of this research. Results: Results indicate that construction workers were willing to wear short-sleeved shirts for …a cooler feeling, although such dressing patterns may not protect them against solar ultraviolet radiation or hazardous substances. Their preferred dark-colored long pants can decrease the direct exposure to solar ultraviolet radiation and hazardous substances, but they absorb a large amount of radiation heat that increases the hazards of heat stress to the wearers. Conclusions: Thermal-related attributes were the most significant concerns of construction workers, which serve as key elements for designing appropriate work clothes for construction workers. Show more

Keywords: Construction workers, dressing behavior, current dressing patterns, work clothing

DOI: 10.3233/OER-140217

Citation: Occupational Ergonomics, vol. 11, no. 4, pp. 177-186, 2013

Article Type: Other

DOI: 10.3233/OER-2013-11406

Citation: Occupational Ergonomics, vol. 11, no. 4, pp. 187-189, 2013

Article Type: Other

DOI: 10.3233/OER-2013-11407

Citation: Occupational Ergonomics, vol. 11, no. 4, pp. 191-192, 2013