Ergonomic evaluation of a new truck seat design: a field study

A postural evaluation of commercial licensed truck drivers was conducted to determine the ergonomic benefits of a truck seat prototype in comparison with an industry standard seat. Twenty commercially licensed truck drivers were recruited to perform a 90-min driving task. Postures were assessed using accelerometers and a backrest and seat pan pressure mapping system. Subjective discomfort measurements were monitored using two questionnaires: ratings of perceived discomfort (RPD) and the automotive seating discomfort questionnaire (ASDQ). Participants reported significantly higher discomfort scores when sitting in the industry standard seat. Participants sat with more lumbar lordosis and assumed a more extended thoracic posture when seated in the prototype. Pairing the gluteal backrest panel with the adjustable seat pan also helped reduce the average sitting pressure on both the seat pan and the backrest. The prototype provided several postural benefits for commercially certified truck drivers, as it did for a young and healthy population.     

An experimental study to evaluate musculoskeletal disorders and postural stress of female craftworkers adopting different sitting postures

This study aimed to evaluate musculoskeletal disorders (MSDs) and postural stress among female craftworkers. The study was carried out on 75 adult female craftworkers in different districts of West Bengal. The prevalence of MSDs, body part discomfort (BPD) rating and body joint angles of the workers were evaluated with standard methods. Electromyography (EMG) of the shoulder and back muscles was recorded with the BIOPAC system. The prevalence of MSDs, BPD rating and deviation of joint angle were comparatively lower in the case of sitting on the floor with folded legs than squatting and sitting on the floor with stretched legs postures. The EMG and rms values of the shoulder and back muscles were comparatively lower in this posture. Therefore, it was concluded that sitting on the floor with folded legs was less hazardous and it imposed less postural stress in comparison to other sitting postures.     

Postural assessment in pen-and-paper-based observational methods and their associated health effects: a review

Introduction. This review describes standardized ergonomics assessment based on pen-and-paper observational methods for assessing ergonomics risk factors. Objective. The three main objectives are to analyze published pen-and-paper observational methods, to extract and understand the risk levels of each method and to identify their associated health effects. Methodology. The authors searched scientific databases and the Internet for materials from 1970 to 2013 using the following keywords: ergo, posture, method, observational, postural angle, health effects, pain and diseases. Postural assessments of upper arms, lower arms, wrists, neck, back and legs in six pen-and-paper-based observational methods are highlighted, extracted in groups and linked with associated adverse health effects. Results. The literature reviewed showed strengths and limitations of published pen-and-paper-based observational methods in determining the work activities, risk levels and related postural angles to adverse health effects. This provided a better understanding of unsafe work postures and how to improve these postures. Conclusion. Many pen-and-paper-based observational methods have been developed. However, there are still many limitations of these methods. There is, therefore, a need to develop a new pen-and-paper-based observational method for assessing postural problems.     

Workstation design in carpet hand-weaving operation: guidelines for prevention of musculoskeletal disorders.

Carpet weavers suffer from musculoskeletal problems mainly attributed to poor working postures. Their posture is mostly constrained by the design of workstations. This study was conducted to investigate the effects of 2 design parameters (weaving height and seat type) on postural variables and subjective experience, and to develop guidelines for workstation adjustments. At an experimental workstation, 30 professional weavers worked in 9 different conditions. Working posture and weavers' perceptions were measured. It was shown that head, neck and shoulder postures were influenced by weaving height. Both design parameters influenced trunk and elbows postures. The determinant factor for weavers' perception on the neck, shoulders and elbows was found to be weaving height, and on the back and knees it was seat type. Based on the results, the following guidelines were developed: (a) weaving height should be adjusted to 20 cm above elbow height; (b) a 10 degrees forward-sloping high seat is to be used at weaving workstations.     

Perceptions of postural stability after transitioning to standing among construction workers

Falls are a leading cause of fatal and nonfatal injuries in the construction trades. This study explored construction workers’ self-reports of postural stability upon standing after working in different postures. One hundred and eighty-nine workers in 10 construction trades provided stability ratings by completing a written questionnaire. Additional data collected included age, gender, years of experience, and rating of overall balance. Construction workers rated their overall balance as high, furthermore, no difference was found between trades or age groups. Significant differences in stability ratings were provided for the various postures. The most commonly used non-erect postures (bent over at waist, squatting, and forward kneeling) resulted in the largest self-reports of instability. Sitting on elevated surface and sitting on level surface resulted in the highest levels of self-reported stability and are recommended when maintaining balance is a concern. Differences associated with construction trade and age were also found, but were thought to be attributed to differences in tasks performed since no differences were found when each posture was analyzed separately. The results suggest that the working posture used to complete a task affects the postural stability upon standing regardless of construction trade and age of worker. Findings may lead to recommendations for redesign of tasks or tools to reduce the use of certain working postures, particularly in high-risk environments such as construction.     

A comparison of three observational techniques for assessing postural loads in industry.

This study aims to compare 3 observational techniques for assessing postural load, namely, OWAS, RULA, and REBA. The comparison was based on the evaluation results generated by the classification techniques using 301 working postures. All postures were sampled from the iron and steel, electronics, automotive, and chemical industries, and a general hospital. While only about 21% of the 301 postures were classified at the action category/level 3 or 4 by both OWAS and REBA, about 56% of the postures were classified into action level 3 or 4 by RULA. The inter-method reliability for postural load category between OWAS and RULA was just 29.2%, and the reliability between RULA and REBA was 48.2%. These results showed that compared to RULA, OWAS, and REBA generally underestimated postural loads for the analyzed postures, irrespective of industry, work type, and whether or not the body postures were in a balanced state.     

Disparity of a Seat Cushion and Its Influence on Postural Control

Properties of supporting surfaces of a seat have an influence on postural control. Centre of pressure (COP) displacement parameters reflect both the balance controlling process and movements of the centre of a mass of entire body. The subjects of the study were 9 healthy men. A seat cushion was examined with a 2-force platform setup. Force exertion at a seat pan and feet and COP displacement at a seat pan were measured to analyse postural control. Analysis of variance determined the differences in postural control depending on a cushion type among the subjects. Significant differences in COP displacement parameters were in COP trajectory length, medio-lateral COP displacement and COP velocity. The results of the study showed that foam cushion ensures better postural control.     

The Impact of Mobile Data Terminal Use on Posture and Low-Back Discomfort When Combined With Simulated Prolonged Driving in Police Cruisers

The introduction of mobile computing within a constrained vehicle environment has led to changes in the task demands of occupational groups such as professional drivers and law enforcement officers. The purpose of this study was to examine how mobile data terminal (MDT) use interacts with prolonged driving to induce postural changes or low-back discomfort. Eighteen participants (9 male, 9 female) completed two 120-min simulated driving sessions. Time-varying lumbar spine and pelvis postures, seat pan interface pressures and ratings of perceived discomfort were recorded at 15-min intervals. The introduction of a computer interface decreased pelvic posterior rotation by an average of 15° with respect to upright standing and increased peak average discomfort in the neck (5.9 mm), left shoulder (6.8 mm), midback (10.9 mm), low back (10.6 mm) and pelvis (11.5 mm) compared to driving alone. The incorporation of mobile computing warrants consideration in the design of vehicle work environments.     

缝纫工慢性肌肉骨骼损伤的调查

缝纫流水线作业工人的慢性肌肉骨骼损伤十分普遍，且涉及面广，如手、腕、肘、臂、肩、颈、背及下肢，其症状与对照人群比，有显著差异。这与他们的工作紧张、工作时间率过多、工中休息时间过少、坐椅过高、工作台面过高及过度低头、向前弯腰等因素有关     

Reality and risk of contact-type head injuries related to bicycle-mounted child seats

Objective

The authors have treated numerous children who have been injured by falling from bicycle-mounted child seats. Despite the greatly increased use of such seats, the understanding of their risk and the importance of helmet use remains alarmingly poor. The objective of this study was to confirm the risk of bicycle-mounted child seats and to evaluate the efficacy of helmets, seat belts, and back seat height in terms of preventing or mitigating contact-type head impacts that occur in falls from bicycle-mounted child seats.

Materials and methods

Biometrical dummy tests were performed to examine contact-type head injuries in falls from stationary bicycles. A bicycle with an anthropometric test dummy placed in a bicycle-mounted child seat was tipped over. Each test was repeated three times and three-dimensional acceleration was measured using accelerometer. Head Injury Criteria (HIC) were calculated and the respective influences of a helmet, a seat belt, and increased height of the back of the seat on such impacts were evaluated.

Results

Only helmets unequivocally lowered maximal acceleration and/or HIC values with statistical significance. The seat belt lowered HIC values as long as it was used with the high-back seat. Only when the dummy wore a helmet sitting in a high-back seat did the HIC show less than the threshold of 570 for three-year-old children. The HIC showed the lowest score of 161.5 when the dummy wore both a helmet and a seat belt sitting in a high-back seat.

Conclusions

Riders in bicycle-mounted child seats definitely have higher risks of contact-type head injuries. In transporting a child on a bicycle-mounted child seat, parents must use both a child-bicycle helmet and a high-back child seat at least; a seat belt is highly recommended as long as it is used with the other safety devices.

Impact on Industry

The bicycle-mounted child seat should have a high enough back and an appropriate seat belt to protect the head of the child from a contact-type injury.     

Posture and belt fit in reclined passenger seats

Abstract

Objective: Highly reclined postures may be common among passengers in future automated vehicles. A laboratory study was conducted to address the need for posture and belt fit in these seating configurations.

Methods: In a laboratory vehicle mockup, the postures of 24 men and women with a wide range of body size were measured in a typical front vehicle seat at seat back angles of 23°, 33°, 43°, and 53°. Data were gathered with and without a sitter-adjusted headrest. Posture was characterized by the locations of skeletal joint centers estimated from digitized surface landmarks.

Results: Regression analysis demonstrated that the pelvis rotated rearward and lumbar spine flexion decreased with increasing recline. The lap portion of the 3-point belt was more rearward relative to the pelvis in more-reclined postures, and the torso portion crossed the clavicle closer to the midline of the body. Regression equations were developed to predict posture and belt fit variables as a function of passenger characteristics, seat back angle, and the use of the headrest.

Conclusions: Spine posture changes as the torso reclines in an automotive seat, and belt fit is altered by the change in posture. The results can be used to accurately position crash test dummies and computation human models and to guide the design of belt restraints.     

THOR dummy chest deflection response in oblique and lateral far-side sled tests

Abstract

Objective: The focus of this study is side impact. Though occupant injury assessment and protection in nearside impacts has received considerable attention and safety standards have been promulgated, field studies show that a majority of far-side occupant injuries are focused on the head and thorax. The 50th percentile male Test Device for Human Occupant Restraint (THOR) has been used in oblique and lateral far-side impact sled tests, and regional body accelerations and forces and moments recorded by load cells have been previously reported. The aim of this study is to evaluate the chestband-based deflection responses from these tests.

Methods: The 3-point belt–restrained 50th percentile male THOR dummy was seated upright in a buck consisting of a rigid flat seat, simulated center console, dashboard, far-side side door structure, and armrest. It was designed to conduct pure lateral and oblique impacts. The center console, dashboard, simulated door structure, and armrest were covered with energy-absorbing materials. A center-mounted airbag was mounted to the right side of the seat. Two 59-gage chestbands were routed on the circumference of the thorax, with the upper and lower chestbands at the level of the third and sixth ribs, respectively, following the rib geometry. Oblique and pure lateral far-side impact tests with and without airbags were conducted at 8.3 m/s. Maximum chest deflections were computed by processing temporal contours using custom software and 3 methods: Procedures paralleling human cadaver studies, using the actual anchor point location and actual alignment of the InfraRed Telescoping Rods for the Assessment of Chest Compression (IR-TRACC) in the dummy on each aspect—that is, right or left,—and using the same anchor location of the internal sensor but determining the location of the peak chest deflection on the contour confined to the aspect of the sensor; these were termed the SD, ID, and TD metrics, respectively.

Results: All deformation contours at the upper and lower thorax levels and associated peak deflections are given for all tests. Briefly, the ID metrics were the lowest in magnitude for both pure lateral and oblique modes, regardless of the presence or absence of an airbag. This was followed by the TD metric, and the SD metric produced the greatest deflections.

Conclusion: The chestbands provide a unique opportunity to compute peak deflections that parallel current IR-TRACC-type deflections and allow computation of peak deflections independent of the initial point of attachment to the rib. The differing locations of the peak deflection vectors along the rib contours for different test conditions suggest that a priori attachment is less effective. Further, varying magnitudes of the differences between ID and TD metrics underscore the difficulty in extrapolating ID outputs under different conditions: Pure lateral versus oblique, airbag presence, and thoracic levels. Deflection measurements should, therefore, not be limited to an instrument that can only track from a fixed point. For improved predictions, these results suggest the need to investigate alternative techniques, such as optical methods to improve chest deflection measurements for far-side occupant injury assessment and mitigation.     

Whole-body vibration and postural stress among operators of construction equipment: a literature review

INTRODUCTION: Operators of construction equipment perform various duties at work that expose them to a variety of risk factors that may lead to health problems. A few of the health hazards among operators of construction equipment are: (a) whole-body vibration, (b) awkward postural requirements (including static sitting), (c) dust, (d) noise, (e) temperature extremes, and (f) shift work. It has been suggested that operating engineers (OEs) are exposed to two important risk factors for the development of musculoskeletal disorders: whole-body vibration and non-neutral body postures. METHOD: This review evaluates selected papers that have studied exposure to whole-body vibration and awkward posture among operators of mobile equipment. There have been only few studies that have specifically examined exposure of these risk factors among operators of construction equipment. Thus other studies from related industry and equipment were reviewed as applicable. CONCLUSION: In order to better understand whole-body vibration and postural stress among OEs, it is recommended that future studies are needed in evaluating these risk factors among OEs.     

Ergonomic analysis of working postures using OWAS in semi-trailer assembly,applying an individual sampling strategy

In semi-trailer assembly, workers are exposed to several physical risk factors. Awkward working postures have not yet been investigated in semi-trailer assembly, although they are known to be a major risk factor for musculoskeletal disorders. We therefore conducted a comprehensive ergonomic analysis of working postures using the Ovako working posture analysing system (OWAS), with an individual sampling strategy. The postural load in semi-trailer assembly was assessed on the basis of 20,601 observations of 63 workers executing a representative set of nine work tasks. According to the OWAS, the postural load of various working postures and body part positions may have a harmful effect on the musculoskeletal system. We therefore give examples of corrective measures that could improve awkward working postures. Applying an individual sampling strategy was revealed to have advantages over a collective strategy, so this is recommended for future ergonomic analyses.     

Relationship between musculoskeletal disorders and anthropometric indices among bus drivers in Zahedan city

Introduction. Most work-related musculoskeletal disorders (MSDs) are associated with improper postures and poorly designed workstations. This study is an attempt to examine the prevalence and severity of MSDs as well as anthropometric dimensions among city bus drivers. Methodology. This cross-sectional study was carried out on 60 male bus drivers. A body discomfort chart was used to evaluate MSDs. Spearman correlation was employed to examine the relationship between body size and the severity of discomfort. Results. Data analysis showed that discomfort reported in the lower back (33.3%), upper back (18.3%) and knee (15%) was severe and there was a direct and significant correlation between the body mass index and the severity of discomfort in the shoulder, arm and hip (p?p?Conclusion. The results of the study can be used to address ergonomic risk factors and reduce their associated disorders. The findings of the study can be used in training programs to educate drivers how to decrease the risk associated with work-related MSDs by adopting appropriate behavior strategies.     

A Study on the Combined Effect of Noise and Vibration on Operators’ Performance of a Readability Task in a Mobile Driving Environment

This paper presents a study in which the main objective was to investigate the combined effect of noise and vibration on the performance of a readability task in a mobile driving environment. Subjects performed a readability task on a laptop computer in a sitting posture with their backs supported with a backrest under varying levels of noise and vibration. The data in terms of the mean number of characters read per minute were collected and statistically analyzed. Results showed that the individual effect of noise, vibration, and the operators’ gender as well as the interaction between gender and noise, and gender and vibration were statistically significant. However, the combined effect of noise and vibration was not found to be statistically significant. Results also indicated that gender was statistically significant at all levels of noise as well as vibration, and noise and vibration were statistically significant at both levels of gender.     

A study on the combined effect of noise and vibration on operators' performance of a readability task in a mobile driving environment.

This paper presents a study in which the main objective was to investigate the combined effect of noise and vibration on the performance of a readability task in a mobile driving environment. Subjects performed a readability task on a laptop computer in a sitting posture with their backs supported with a backrest under varying levels of noise and vibration. The data in terms of the mean number of characters read per minute were collected and statistically analyzed. Results showed that the individual effect of noise, vibration, and the operators' gender as well as the interaction between gender and noise, and gender and vibration were statistically significant. However, the combined effect of noise and vibration was not found to be statistically significant. Results also indicated that gender was statistically significant at all levels of noise as well as vibration, and noise and vibration were statistically significant at both levels of gender.     

Analysis of Conditions and Organization of Work of Notebook Computer Users

Abstract

Aim. The aim of this study was to evaluate working conditions with a notebook computer (notebook) as a potential cause of musculoskeletal disorders. Material and methods. The study had 2 stages. The first one was a questionnaire survey among 300 notebook users. The next stage was an expert analysis of 53 randomly selected workstations. The questionnaire survey included questions about the participants, their working conditions, work organization and also duration of work with a notebook. Results and conclusions. The results of the research showed that most examined operators used a notebook as a basic working tool. The most important irregularities included an unadjustable working surface, unadjustable height of the seat pan and backrest, unadjustable height and distance between the armrests and no additional ergonomic devices (external keyboard, docking station, notebook stand or footstool).     

Physical limitations and musculoskeletal complaints associated with work in unusual or restricted postures: a literature review

INTRODUCTION: The vast majority of ergonomics research has addressed the demands of work in standing or sitting postures, and understandably so. However, many workers (e.g., underground miners, aircraft baggage handlers, plumbers, agricultural workers, mechanics, and others) are often required to adopt postures such as kneeling, stooping, squatting, or lying down for significant periods of the workday. METHOD: A literature search was performed using the ISI Web of Science database (for years 1980-2004). Articles retrieved from this search were evaluated in terms of relevance to assessing physical capabilities of workers in these postures and/or the musculoskeletal epidemiology associated with these postures. RESULTS: Work in unusual and restricted postures was associated with significantly higher rates of musculoskeletal complaints compared to workers not adopting these postures in epidemiology studies (Odds Ratios ranging from 1.13 to 13). Some studies suggested a dose-response relationship, with longer exposures leading to increased musculoskeletal complaints. Physical strength and psychophysical lifting capacity vary significantly as unusual or restricted postures are adopted, with lower lifting capacities evident in the kneeling, squatting, and lying positions. CONCLUSIONS: Workers who adopt unusual or restricted postures appear to be at higher risk of musculoskeletal complaints and often exhibit reduced strength and lifting capacity. Research needs in this area include improved exposure assessment tools, studies of intervention effectiveness, adaptations of the body in response of work in unusual postures, and elucidation of relevant injury pathways. IMPACT ON INDUSTRY: Workers who adopt unusual or restricted postures in their work often experience higher musculoskeletal injury rates. If awkward postures cannot be eliminated in the workplace, jobs should be designed in accordance with the reduced strength and lifting capabilities observed in these postures.