Chosen postures during specific sitting activities

This research study analysed the interaction between people's postures and activities while in semi-public/leisure situations and during transportation (journey by train). In addition, the use of small electronic devices received particular emphasis. Video recordings in German trains and photographs in Dutch semi-public spaces were analysed using a variation of Branton and Grayson's (An evaluation of train seats by observation of sitting behaviour. Ergonomics, 10 (1), (1967), 35-51) postural targeting forms and photos. The analysis suggests a significant relationship between most activities and the position of the head, trunk and arms during transportation situations. The relationship during public situations is less straightforward. Watching, talking/discussing and reading were the most observed activities for the transportation and leisure situations combined. Surprisingly, differences in head, trunk, arm and leg postures were not significant when using small electronic devices. Important issues not considered in this study include the duration of the activities, the gender and age of observed subjects and the influence of the time of day. These are interesting issues to consider and include for future research. STATEMENT OF RELEVANCE: This study shows what activities people choose to carry out and their related postures when not forced to a specific task (e.g. driving). The results of this study can be used for designing comfortable seating in the transportation industry (car passenger, train, bus and aircraft seats) and semi-public/leisure spaces.     

Activities,postures and comfort perception of train passengers as input for train seat design

Working in the train is a part of new ways of working. However, the ideal working position is unknown. Moreover, the ideal position for leisure and relaxing is also unknown. This article defines what activities train passengers mainly perform and which corresponding postures are seen. Based on the observations on actual train rides, four main activities could be identified: Reading, Staring/sleeping, Talking and Working on laptop. Working on laptop was the activity with the longest duration and talking had the shortest duration. Associated with these four activities, a top eight of different postures were observed. Except for headrest comfort, comfort scores were not significantly different between activities. The top eight corresponding postures combined with comfort scores showed that per activity different postures were observed and the comfort scores varied in relation to the combination of posture and activity. Nearly for all activities, the majority of passengers preferred adjustability options to fit the seat to the performed activity.     

An analysis of scanning postures among grocery cashiers and its relationship to checkstand design

Mounting evidence suggests that musculoskeletal disorders are prevalent among US retail food workers. Cashiers who use electronic scanners appear to be at especially high risk for upper extremity musculoskeletal disorders. Checkstand design has been implicated as a contributor to musculoskeletal injury among cashiers because workstation design can significantly impact working posture. The present study examines working posture among two groups of cashiers to determine if checkstand design is associated with substantial differences in posture and movement during scanning. The work activities of twenty grocery cashiers using one of two checkstand designs (front-facing and right-hand takeaway) were examined. Videotapes of cashiers performing scanning tasks were observed and associated postures and movements were visually coded. The right-hand takeaway design was associated with a significantly higher percentage of non-neutral trunk postures than the front-facing design. However, there were no significant differences in shoulder posture, grasp, or scanning motion associated with checkstand/scanner design. Factors that appeared to affect cashier work posture during scanning included stature, order size, and product type. Although improving the checkstand design may reduce the occurrence of certain awkward postures and static muscle loading conditions among cashiers, the success of these interventions is likely to be limited unless follow-up programmes are instituted to ensure that cashiers are able to use these designs effectively. Furthermore, fundamental changes in cashier work may be required to fully eliminate hazards for musculoskeletal disorders from this job.     

A study stressing the need for a static postural force model for work analysis

The maximum endurance time (MET) in static force exertions was used as a parameter for the assessment of five working postures. By applying the methodology of Rohmert to the construction of a general model for static muscular work and evaluating the measured MET results, the need for a new static posture model has been shown.

The aim of the present pilot study was to test MET in load situations that would indicate when the general model can be used or when a new static postural force model is needed.

Subjects exerted static postural forces at different load levels until exhaustion. In the first two postures, the strain was concentrated on the upper limbs, where active forces (muscular) play a key-role and justify the use of the model. In the remaining postures, the strain affected mainly the back/trunk, where the mechanical equilibrium of the body is brought about by active (muscles) and passive (skeleton and ligaments) structures.

During the tests electromyographic (EMG) measurements of selected muscles (objective measurements) as well as rated perceived exertion (RPE; subjective measurements on Borg's CR-10 scale) were recorded.

The results show that the maximum endurance times in upper extremity postures are predicted by the general model whilst in the back/trunk postures the measured MET was longer than predicted by the model. New models are presented for static postural force on the back.

The EMG measurements supported the conclusion that the muscles studied play a key role in the chosen upper-extremity postures but gave no clear indication in the back-oriented postures. Ratings of perceived exertion coincided with the EMG measurements in upper extremity postures and proved to be a good substitute for measurement and calculation of the load levels studied. The initial RPE can therefore be used in models for predicting maximal endurance times in complex cases.

For the range of relative postural loads tested, an exponential function for predicting MET in static posture exertions produced the best fit curve.     

Towards exposure limits for working postures and musculoskeletal symptoms – a prospective cohort study

Occupational postures are considered to be an important group of risk factors for musculoskeletal pain. However, the exposure-outcome association is not clear yet. Therefore, we aimed to determine the exposure-outcome association of working postures and musculoskeletal symptoms. Also, we aimed to establish exposure limits for working postures. In a prospective cohort study among 789 workers, intensity, frequency and duration of postures were assessed at baseline using observations. Musculoskeletal pain was assessed cross-sectionally and longitudinally and associations of postures and pain were addressed using logistic regression analyses. Cut-off points were estimated based on ROC-curve analyses. Associations were found for kneeling/crouching and low-back pain, neck flexion and rotation and neck pain, trunk flexion and low-back pain, and arm elevation and neck and shoulder pain. The results provide insight into exposure-outcome relations between working postures and musculoskeletal symptoms as well as evidence-based working posture exposure limits that can be used in future guidelines and risk assessment tools.

Practitioner Summary: Our study gives insight into exposure-outcome associations of working postures and musculoskeletal symptoms (kneeling/crouching and low-back pain, neck flexion/rotation and neck pain, trunk flexion and low-back pain, and arm elevation and neck and shoulder pain). Results furthermore deliver evidence-based postural exposure limits that can be used in guidelines and risk assessments.     

An evaluation of backpack harness systems in non-neutral torso postures

Much of the research on backpack design has been focused on spinal loading/biomechanics while the wearer is in a neutral/upright trunk posture, such as those employed by outdoor enthusiasts and schoolchildren. This research has led to some important harness design improvements that reduce trunk muscle exertions, fatigue and improve overall comfort. There are number of occupations, however, wherein workers wear back-mounted packs/devices (e.g. air tanks) while working in non-neutral trunk postures. The objective of the current study was to evaluate the effects of these non-neutral postures on biomechanical loading and then reconsider the backpack system design recommendations. Fifteen participants were asked to support a 18.2 kg load on their back while assuming static forward flexed postures of the torso (15 degrees , 30 degrees , 45 degrees , and 60 degrees of sagittal bend). The mass on the back was attached to the participant through two different harness mechanisms: a basic harness design (as seen on college student backpacks) and a more advanced design containing lateral stiffness rods and a weight-bearing hip belt (as seen on backpacks for hikers). While performing these static, posture maintenance tasks, the activation levels of the bilateral trapezius, erector spinae, and rectus abdominis were collected. Participants also provided subjective ratings of comfort. The results showed that there was a significant interaction between harness type and forward flexion angle for the trapezius and the erector spinae muscles. The normalized EMG for the trapezius muscles showed a 14% and 11% reduction in muscle activity at 15 degrees and 30 degrees , respectively, with the advanced design but these positive effects of the advanced design were not found at the greater flexion angles. Likewise the erector spinae muscles showed a 24% and 14% reduction in muscle activity at 15 degrees and 30 degrees , respectively, with the advanced design harness but these effects of the advanced design were not found at the greater forward flexion angles. The level of forward flexion angle affected the rectus abdominis muscle activity, but neither the harness type main effect nor the interaction of harness type and forward flexion angle was significant. The subjective survey results agreed with the EMG results and showed the advanced design harness was generally more comfortable with respect to the shoulder and low back areas. Collectively, the subjective and objective results show a significant improvement with the advanced harness system but also note an interesting interaction with degree of sagittal flexion, indicating a diminished effectiveness of the design improvements at forward flexed postures. Design criteria for harness systems in these forward flexed postures are discussed.     

Macro repositioning movements of pelvis and trunk during simulated driving tasks

Low back pain (LBP)³ is one of the most important features of discomfort in prolonged sitting postures. This is evidenced by an increase in the number of postural changes called macro-movements. The focus of study was the frequencies of macro repositioning movements in prolonged sitting posture resulting from the perception of discomfort caused by low-back pain. Eighteen (18) drivers performed driving tasks for a period of 90 min. The results indicate that LBP participants performed more movements (10.52 rep/h), compared to without low back pain participants (8.52 rep/h). However, the latter moved more than expected due to joint macro movements of the pelvis and trunk. LBP subjects generally performed macro-repositioning movements of the trunk only, while without low back pain (WLBP)⁴ subjects moved pelvis and trunk simultaneously. Although the WLBP participants moved less than those with LBP symptoms, they applied different movement strategies which should be considered in further research. Finally, the authors also propose that future research should be directed towards determining the influence of these lumbo pelvic movements when provided in a controlled manner, to improve comfort in seats and to help manufactures to offer better ergonomic seats.Relevance to industryAccording to the findings of this study, control of lumbo pelvic movements could be used to improve the design and production of ergonomic seats for driving activities.     

A checklist for evaluating ergonomic risk factors resulting from awkward postures of the legs, trunk and neck

A one-page checklist for determining the presence of ergonomic risk factors associateed with awkward postures of the lower extremities, trunk and neck was developed and evaluated as part of a joint labor-management ergonomics intervention program. This checklist was used by plant personnel at four work sites to assess the postural requirements on 335 cyclical (i.e., work-cycle duration less than five minutes) manufacturing and warehouse jobs. In addition, results generated by the checklist were compared to the results of ergonomic analyses performed by persons with advanced training in occupational ergonomics.

Workers were observed using awkward postures for most of the jobs in the survey. Awkward postures of the lower extrimities were relatively uncommon, occuring in 25 percent or less of the jobs. Awkward postures of the trunk and neck were common, occuring in more than 70 percent of the jobs. Results generated by the checklist were generally in agreement with results generated by the experienced ergonomists; however, the checklist was found to be more sensitive in identifying the presence of awkward postures.

The checklist was found to be an effective rapid-screening instrument for identifying cyclical jobs that expose workers to potentially harmful postures. However, the checklist methodology did not include sufficient documentation of work methods to identify the specific job attributes associated with these exposures. Furthermore, the checklist was not used to evaluate non-cyclical jobs (e.g., maintenance and skilled trades).     

Paramedics on the job: Dynamic trunk motion assessment at the workplace

Many paramedics' work accidents are related to physical aspects of the job, and the most affected body part is the low back. This study documents the trunk motion exposure of paramedics on the job. Nine paramedics were observed over 12 shifts (120 h). Trunk postures were recorded with the computer-assisted CUELA measurement system worn on the back like a knapsack. Average duration of an emergency call was 23.5 min. Sagittal trunk flexion of >40° and twisting rotation of >24° were observed in 21% and 17% of time-sampled postures. Medical care on the scene (44% of total time) involved prolonged flexed and twisted postures (∼10 s). The highest extreme sagittal trunk flexion (63°) and twisting rotation (40°) were observed during lifting activities, which lasted 2% of the total time. Paramedics adopted trunk motions that may significantly increase the risk of low back disorders during medical care and patient-handling activities.     

Test-retest reliability and concurrent validity of a web-based questionnaire measuring workstation and individual correlates of work postures during computer work

INTRODUCTION: "Ergonomic" questionnaires are widely used in epidemiological field studies to study the association between workstation characteristics, work posture and musculoskeletal disorders among office workers. Findings have been inconsistent regarding the putative adverse effect of work postures. Underestimation of the true association might be present in studies due to misclassification of subjects to risk (i.e. exposed to non-neutral working postures) and no-risk categories (i.e. not exposed to non-neutral working postures) based on questionnaire responses. The objective of this study was to estimate the amount of misclassification resulting from the use of questionnaires. METHODS: Test-retest reliability and concurrent validity of a newly developed questionnaire was assessed. This questionnaire collects data on workstation characteristics and on individual characteristics during computer work (i.e. work postures, movements and habits). Pictures were added where possible to provide visual guidance. The study population consisted of 84 office workers of a research department. They filled out the questionnaire on the Internet twice, with an in-between period of 2 weeks. For a subgroup of workers (n=38), additional on-site observations and multiple manual goniometer measurements were performed. RESULTS: Percentage agreement ranged between 71% and 100% for the test-retest analysis, between 31% and 100% for the comparison between questionnaire and on-site observation, and between 26% and 71% for the comparison between questionnaire and manual goniometer measurements. For 9 out of 12 tested items, the percentage agreement between questionnaire and manual goniometer measurements was below 50%. CONCLUSIONS: The questionnaire collects reliable data on workstation characteristics and some individual characteristics during computer work (i.e. work movements and habits), but does not seem to be useful to collect data on work postures during computer work in epidemiological field studies among office workers.     

Coach design for the Korean high-speed train: a systematic approach to passenger seat design and layout

Proper ergonomic design of a passenger seat and coach layout for a high-speed train is an essential component that is directly related to passenger comfort. In this research, a systematic approach to the design of passenger seats was described and the coach layout which reflected the tradeoff between transportation capacity and passenger comfort was investigated for the Korean high-speed train. As a result, design recommendations and specifications of the passenger seat and its layout were suggested. The whole design process is composed of four stages. A survey and analysis of design requirement was first conducted, which formed the base for designing the first and second class passenger seats. Prototypes were made and evaluated iteratively, and seat arrangement and coach layout were finally obtained. The systematic approach and recommendations suggested in this study are expected to be applicable to the seat design for public transportations and to help modify and redesign existing vehicular seats.     

Trunk postural demands of occupational activities of some merchant pregnant women in Benin,West Africa

Strenuous physical work puts expectant mothers at risk of experiencing back pain during the gestational months. Pregnant women in Benin perform physically demanding occupational tasks that include the lifting and carriage of heavy loads on their heads for commercial activities. A large percentage of pregnant subjects (58%) reported having back pain episodes since the start of their pregnancy. However, the mean Oswestry score of the affected participants was relatively low with a mean score of 0.2 (SD: 0.12), on a scale form 0 to 1. An evaluation of the postural demands of the occupational activities of these women revealed that they performed on average 328 trunk flexions at angles exceeding 60°, with 66 of these flexions sustained for more than 4 s, during the average 7.9 h where trunk postures were recorded. They also spent on average 36% of the recording time at trunk flexion angles larger than 20°. These results show that the merchant pregnant women in the Porto-Novo area in Benin are at great risk for developing back disorders during pregnancy.

Practitioner Summary: Results will make a first contribution to the literature by identifying the stressful postures adopted during a typical day. The findings of this study can help in the development of preventative concepts and postural modification techniques to decrease the occurrence of back pain during pregnancy for women in Benin.     

Studying the relationship between low back pain and working postures among those who stand and those who sit most of the working day

A relationship between low back pain (LBP) and prolonged standing or prolonged sitting at work has not been clearly shown, despite its biological plausibility. Because sitting and standing postures vary as to duration and freedom to alternate postures, and standing postures vary as to mobility, associations between specific working postures and LBP were explored using multiple logistic regression. Associations between work factors and self-reported LBP during the previous 12 months that interfered with usual activities were examined among 4493 standing workers and 3237 sitting workers interviewed in the 1998 Quebec Health and Social Survey; 24.5% reported significant LBP. Since the same conditions can correspond to different physiological demands for sitting compared with standing workers, analyses were performed separately for the two groups. Standing without freedom to sit was associated with LBP. Different occupational physical and psychosocial factors were associated with LBP in sitting compared with standing populations.     

Posture Targeting: A Technique for Recording Working Postures

Abstract

A technique is described for recording whole body postures by making ten marks on a chart, these marks indicating the positions of the head, trunk, upper and Sower limbs with reference to a standard position. Training in the technique was given to groups of subjects, including 32 work study practitioners, and tests of accuracy and repeatability conducted. The procedure was found to be easy to learn, highly repeatable and accurate except where postures were held for short periods and not repeated.     

Effects of posture on dynamic back loading during a cable lifting task

This study evaluated spinal loads associated with lifting and hanging heavy mining cable in a variety of postures. This electrical cable can weigh up to 10 kg per metre and is often lifted in restricted spaces in underground coal mines. Seven male subjects performed eight cable lifting and hanging tasks, while trunk kinematic data and trunk muscle electromyograms (EMGs) were obtained. The eight tasks were combinations of four postures (standing, stooping, kneeling on one knee, or kneeling on both knees) and two levels of cable load (0 N or 100 N load added to the existing cable weight). An EMG-assisted model was used to calculate forces and moments acting on the lumbar spine. A two-way split-plot ANOVA showed that increased load (p < 0.05) and changes in lifting posture (p < 0.05) independently affected trunk muscle recruitment and spinal loading. The increase in cable load resulted in higher EMG activity of all trunk muscles and increased axial and lateral bending moments on the spine (p < 0.05). Changes in posture caused more selective adjustments in muscle recruitment and affected the sagittal plane moment (p < 0.05). Despite the more selective nature of trunk EMG changes due to posture, the magnitude of changes in spinal loading was often quite dramatic. However, average compression values exceeded 3400 N for all cable lifting tasks.     

Interaction with a smartphone under different task and environmental conditions: Emergence of users’ postural strategies

Nowadays, interactions with smartphones are constantly increasing. These devices are used in a wide variety of situations by performing various tasks. The purpose of this study is to determine whether one or more strategies emerge when subjects freely send message and browse on the web in three environmental conditions: sitting with or without support and standing. Therefore, a hierarchical cluster analysis (HCA) was applied to the angular parameters of the neck and trunk as well as to the distance between the face and the telephone. These 3D motion analysis data were also processed taking into account the ergonomic recommendations from the Rapid Upper Limb Assessment in order to qualify the postural strategies highlighted by the HCA. The findings showed that there are three different postural strategies adopted by the subjects especially in the sagittal plane: a first one involves the neck without implying the trunk; a second one strongly mobilizes the trunk flexion without involving the neck; and a third postural strategy which combines these two behaviors. These three postural strategies depend on the environmental condition. Indeed, the postural strategy involving the trunk is associated with the presence of a support while the one involving the neck only appears in conditions without support. It is also observed that smartphone users mainly adopt harmful postures, whether due to excessive flexion of the neck, trunk or both. Even when subjects place themselves in the least harmful postures, there are always risks of musculoskeletal disorders in the short or long term.     

Trunk postures and upper-body muscle activations during physically demanding wildfire suppression tasks

This study examined the trunk postures and upper-body muscle activations during four physically demanding wildfire suppression tasks. Bilateral, wireless surface electromyography was recorded from the trapezius and erector spinae muscles of nine experienced, wildfire fighters. Synchronised video captured two retroreflective markers to allow for quantification of two-dimensional sagittal trunk flexion. In all tasks, significantly longer time was spent in the mild and severe trunk flexion (p ≤ 0.002) compared to the time spent in a neutral posture. Mean and peak muscle activation in all tasks exceeded previously established safe limits. These activation levels also significantly increased through the performance of each task (p < 0.001). The results suggest that the wildfire suppression tasks analysed impose significant musculoskeletal demand on firefighters. Fire agencies should consider developing interventions to reduce the exposure of their personnel to these potentially injurious musculoskeletal demands.     

Effects of posture on dynamic back loading during a cable lifting task

This study evaluated spinal loads associated with lifting and hanging heavy mining cable in a variety of postures. This electrical cable can weigh up to 10 kg per metre and is often lifted in restricted spaces in underground coal mines. Seven male subjects performed eight cable lifting and hanging tasks, while trunk kinematic data and trunk muscle electromyograms (EMGs) were obtained. The eight tasks were combinations of four postures (standing, stooping, kneeling on one knee, or kneeling on both knees) and two levels of cable load (0 N or 100 N load added to the existing cable weight). An EMG-assisted model was used to calculate forces and moments acting on the lumbar spine. A two-way split-plot ANOVA showed that increased load (p<0.05) and changes in lifting posture (p<0.05) independently affected trunk muscle recruitment and spinal loading. The increase in cable load resulted in higher EMG activity of all trunk muscles and increased axial and lateral bending moments on the spine (p<0.05). Changes in posture caused more selective adjustments in muscle recruitment and affected the sagittal plane moment (p<0.05). Despite the more selective nature of trunk EMG changes due to posture, the magnitude of changes in spinal loading was often quite dramatic. However, average compression values exceeded 3400 N for all cable lifting tasks.     

Posture analysis among Flemish secondary school teachers: difference between the use of chalkboards and electronic school boards during classroom teaching

The aim of this study was to (i) make a posture analysis of teachers during theoretical classroom teaching; (ii) to estimate the risk for the development of musculoskeletal problems (MSP); (iii) test the hypotheses that an electronic school board (EB) has more ergonomic advantages for teachers. Thirty-five secondary school teachers, of which 15 used an EB and 20 used chalkboards, were selected by convenience sampling and filmed during 30 min of a theoretical course. Posture analysis of back, arms, legs and risk assessment was performed using the Ovako Working Posture Analysis System. Most of the teachers’ postures did not indicate a higher risk for MSP. However, some postures may be harmful when accumulated for several hours of teaching a day; especially, long periods of standing and standing with a bended back. Results also indicated that currently the use of an EB does not improve teachers’ posture.

Practitioner Summary: The relationship between objectively measured physical work load and risk for injuries among teachers was not analysed so far. In this study teachers’ posture was analysed using the OWAS method. Prolonged standing and forward bending were identified as risk postures. Also, using an electronic school board currently does not improve posture.