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Effects of differences in office chair controls, seat and backrest angle design in relation to tasks
Abstract
In this study the influence of chair characteristics on comfort, discomfort, adjustment time and seat interface pressure is investigated during VDU and non-VDU tasks: The two investigated office chairs, both designed according to European and Dutch standards are different regarding: 1) seat cushioning and shape, 2) backrest angle and 3) controls. Thirty subjects in total, both male and female, participated in two experiments: twenty in the first and ten in the second. Significant differences are found for ease of adjustment and adjustment time of controls, independent of the tasks. Related to tasks, a significant difference was found for the backrest range of motion. For non-VDU tasks a larger range of backrest motion was preferred by 70% of the subjects. The chair design differences were most clear for comfort and adjustment time of controls, followed by comfort of backrest angle. No differences are found between seat pan comfort and discomfort, first impressions and peak interface pressure.
... Office workers spend about 82% of their working time in a sitting position. Office work typically involves a prolonged static work posture, repetitive movements, and inappropriate hand and spine positions during work (19,20). For this reason, musculoskeletal disorders are very common among office workers (8,9,19). ...
... Office work typically involves a prolonged static work posture, repetitive movements, and inappropriate hand and spine positions during work (19,20). For this reason, musculoskeletal disorders are very common among office workers (8,9,19). It has been reported that a chair that meets ergonomic requirements can be beneficial in reducing musculoskeletal symptoms and preventing spinal problems (7). ...
... This may be due to the large standard deviation in UT and the fact that the participants could not adapt to the chair adequately because they were using the chairs for the first time during the measurement. Several studies have shown that a well-adjustable ergonomic chair increases productivity and reduces musculoskeletal complaints (19,21). For this reason, before the measurements, the participants were shown the adjustments of the chair. ...
Background and Purpose: Musculoskeletal disorders (MSD) are one of the most common health problems faced by individuals who sit for prolonged periods. The sitting design of office chairs has recently become an important aspect in preventing the MSD. The aim of this study is to determine the effect of different chair types on trunk muscle activation. Methods: Fifteen participants (age 22.92 ± 3.40 years) were included in the study. Participants’ muscle activations were assessed with the sEMG device while sitting and typing on the computer for one hour. Results: When two different types of chairs were compared, in the first 10 minutes, % MVC difference was observed only in the TES (p<0.05). Also, %MVC difference was found only in the TrA/IO (p<0.05) during the last 10 minutes. No significant difference was identified in two chair types in terms of activation of UT (p>0.05). Conclusions: It was shown that ergonomic chair may not significantly alter the activation of UT, TES, and TrA/IO muscles compared to the standard type. Therefore, the use of ergonomic chairs suitable for the physiological needs of individuals should be recommended in order to encourage increased trunk muscle activation during prolonged sitting.
... Power seats (i.e., electrically adjustable seats that can move in several ways) with electrical control, for example, electrical backrest adjustment, are widely used in airplanes, vehicles, and offices for safety, convenience, and comfort. The speed of moving seat components, for example, the backrest and the seat pan, during an adjustment can influence subjective preference for a seat and could be related to the overall comfort of a seat [1]. In contrast to "comfort", "discomfort" is commonly used to describe subjective reactions (e.g., annoying, uncomfortable, and distressed) to environmental stresses, mainly associated with pain, tiredness, soreness, and numbness [2][3][4]. ...
... The inclination of a backrest significantly affects an occupant's static comfort, and many studies have been conducted to determine the most appropriate angle for static comfort [1,[7][8][9]. Haynes and Williams [7] asked subjects to complete typing tasks in different sitting postures and concluded that different sitting postures as a result of different backrest angles (100 • , 125 • , and 160 • ) and seat tilt angles (5 • and 40 • ) led to significant differences in typing performance and comfort. Wang and Cardoso [9] indicated that seat discomfort decreased with an increase in backrest angle. ...
... Vink and Lips [27] indicated that there were significant differences between males and females regarding sensitivity to pressure from the backrest and the seat pan. Subjects with different statures preferred different sizes of seats; relatively, taller subjects reported less discomfort in larger seats than in smaller seats, and vice-versa [1,8]. Na and Lim [28] reported that stature showed significant effects on local discomfort in the neck, shoulders, hips, and thighs. ...
Power seats (i.e., electrically adjustable seats that can be designed to move in several ways) have become increasingly common in airplanes, vehicles, and offices. Many studies have investigated the effects of seat attitude parameters, for example, the inclined angles of a backrest, on discomfort during the adjustment process. However, few studies have considered discomfort under different speeds during the adjustment process. In this study, we investigated discomfort with three speeds (i.e., “fast”, “median”, and “slow” corresponding to three durations of 15, 20, and 25 s, respectively) and two adjustments of a power seat, i.e., incline angle adjustment of the backrest and fore-andaft position adjustment of the seat pan. We also investigated the effects of different physiological parameters on subjects’ discomfort. Twenty-four subjects (12 males and 12 females) completed a questionnaire to indicate their adjustment condition preferences, to rate their overall discomfort during the adjustment processes on a category-ratio scale, and to rate their local body discomfort. The majority of subjects preferred the fast speed adjustment condition and the trend was that a lower backrest adjustment speed increased discomfort during the process. The dominant local discomfort was in the upper and lower back regions during the backrest adjustment, whereas there was no obvious dominant local discomfort during the seat pan adjustment. The physiological parameters also had significant correlations with discomfort in some adjustment movements, for example, the discomfort was negatively correlated with height during the backrest adjustment.
... Power seats (i.e., electrically adjustable seats that can move in several ways) with electrical control, for example, electrical backrest adjustment, are widely used in airplanes, vehicles, and offices for safety, convenience, and comfort. The speed of moving seat components, for example, the backrest and the seat pan, during an adjustment can influence subjective preference for a seat and could be related to the overall comfort of a seat [1]. In contrast to "comfort", "discomfort" is commonly used to describe subjective reactions (e.g., annoying, uncomfortable, and distressed) to environmental stresses, mainly associated with pain, tiredness, soreness, and numbness [2][3][4]. ...
... The inclination of a backrest significantly affects an occupant's static comfort, and many studies have been conducted to determine the most appropriate angle for static comfort [1,[7][8][9]. Haynes and Williams [7] asked subjects to complete typing tasks in different sitting postures and concluded that different sitting postures as a result of different backrest angles (100 • , 125 • , and 160 • ) and seat tilt angles (5 • and 40 • ) led to significant differences in typing performance and comfort. Wang and Cardoso [9] indicated that seat discomfort decreased with an increase in backrest angle. ...
... Vink and Lips [27] indicated that there were significant differences between males and females regarding sensitivity to pressure from the backrest and the seat pan. Subjects with different statures preferred different sizes of seats; relatively, taller subjects reported less discomfort in larger seats than in smaller seats, and vice-versa [1,8]. Na and Lim [28] reported that stature showed significant effects on local discomfort in the neck, shoulders, hips, and thighs. ...
Power seats (i.e., electrically adjustable seats that can be designed to move in several ways) have become increasingly common in airplanes, vehicles, and offices. Many studies have investigated the effects of seat attitude parameters, for example, the inclined angles of a backrest, on discomfort during the adjustment process. However, few studies have considered discomfort under different speeds during the adjustment process. In this study, we investigated discomfort with three speeds (i.e., “fast”, “median”, and “slow” corresponding to three durations of 15, 20, and 25 s, respectively) and two adjustments of a power seat, i.e., incline angle adjustment of the backrest and fore-and-aft position adjustment of the seat pan. We also investigated the effects of different physiological parameters on subjects’ discomfort. Twenty-four subjects (12 males and 12 females) completed a questionnaire to indicate their adjustment condition preferences, to rate their overall discomfort during the adjustment processes on a category-ratio scale, and to rate their local body discomfort. The majority of subjects preferred the fast speed adjustment condition and the trend was that a lower backrest adjustment speed increased discomfort during the process. The dominant local discomfort was in the upper and lower back regions during the backrest adjustment, whereas there was no obvious dominant local discomfort during the seat pan adjustment. The physiological parameters also had significant correlations with discomfort in some adjustment movements, for example, the discomfort was negatively correlated with height during the backrest adjustment.
... examined pressure around the left buttock and on the is chialtubercle [6,7], M.P. DeLooze et all.uniform distribution of pressure in the seat pan and chair back [4], S.M. Carconeand P.J. Keir studied the area of contact with the seat and the average pressure in the seat [3], and also in some studies the maximum pressure in the seat was studied [3,8,10]. ...
... Eight tests were carried out in various sitting positions (Table 1). (1) Sitting legs under a chair (2) Sitting elbows on knees (3) Sitting elbows on knees with mobile phone (4) Sittingleft leg on the right (5) Sitting right leg on the left (6) Sitting back relaxed (7) Sitting with hands on a table (8) Statistical analysis of the results was carried out using the STATISTICA 10.0 program. The calculation of Mean, Standard Deviation, Spearman, 2D Scatterplot (graphtype -Regular, fittype -linear), as well as linear regression analysis was performed. ...
... The smallest WMEAN values were observed in the sitting elbows on knees (3) position, the highest in sitting legs under a chair (2). Figure 1 shows the relative dynamics of WMEAN (WMEAN when Sitting straight is taken as 100%). (6).In the range of 20-30% is Sitting back relaxed (7), in the range of 40-50% -Sitting with hands on a table (8), in the range of 60-80% -Sitting elbows on knees (3) and Sitting elbows on knees with mobile phone (4). The most difficult for chair posture detection are the poses Sitting left leg on the right and Setting right leg on the left, because their WMEAN values are very close to Sitting straight. ...
The purpose of the article is to determine the possibility of diagnosing various sitting positions according to the dynamics of WMEAN. Materials and methods: 19 people (10 males and 9 females) aged from 16 to 50 years were examined. The Force platform MBN "Stabilo" was installed on a chair and 8 tests were carried out with various poses followed by the analysis of the dynamics of WMEAN (kg). Results: Spearman correlation results show high r values (from 0.87 to 0.96, p≤0.05).According to the 2D Scatterplot, an almost linear dependence was revealed, regression equations were obtained for each pose. Conclusion: the possibility of creating an equipment for tracking the time of the "right / wrong" position using the WMEAN tracking algorithm is shown.
... In addition, studies on (dis)comfort may be accompanied by anthropometric evaluations [13,14]. Groenesteijn et al. [15] reported that taller users rated larger sized seats more comfortable, while shorter users rated smaller seats as more comfortable. The authors found that worker performance and muscular comfort were improved as a result of workstation adjustments [15]. ...
... Groenesteijn et al. [15] reported that taller users rated larger sized seats more comfortable, while shorter users rated smaller seats as more comfortable. The authors found that worker performance and muscular comfort were improved as a result of workstation adjustments [15]. Apparently, work setting adjustment could minimize the muscular load and optimize user performance [16]. ...
... Thus, improvements in seat design such as seat and backrest inclination, headrest adjustability, improvement of space and, mainly, leg space are important issues in chair comfort [30]. In a study by Groenesteijn et al. [15], it was shown that seat comfort was good and seat discomfort was low after prolonged sitting, which is not similar to our findings. ...
The aim of this study was to determine optimum seat depth using subjective assessments. Comfort and discomfort evaluation, as an ergonomic subjective method, was used to find the optimum seat depth. A total of 36 university students rated the comfort and discomfort of 6 different seat depths (including 32.0 cm, 37.0 cm, 42.0 cm, 47.0 cm and 52.0 cm which covered the buttock–popliteal length [BPL] range as well as 40.2 cm representing the 5th percentile of the BPL) during a 90-minute time period using the chair evaluation checklist (CEC). The results showed that the seat depth of 40.2 cm (equivalent to 5th percentile of BPL) was more comfortable and caused less discomfort ratings after 90 minutes compared to other experimental seat depths. The findings suggest that appropriate seat depth for the studied population can be recommended based on the 5th percentile of the BPL as an anthropometric criterion.
... Asundi et al. [5] performed an experimental study on the effects on posture of using a notebook on lap, desk, and lap-desk support which mentions the body and seat angles for using the notebook. Groenesteijn et al. [6] performed a study on office chairs for designing a seat and backrest in relation to different tasks which provides the information on the seat angles for different tasks. Nicholson et al. [7] published a paper on the influence of back angle on the quality of sleep in seats. ...
... Out of these twelve papers, only four papers include information related to experimental design and the participation of subjects (e.g. Groenesteijn [6]). The remaining eight papers are either journals, text books, articles or published papers which do not mention any information about the experimental design data (e.g. ...
... Haynes et al. [10] compared the overall comfort with six subjects for typing tasks on a computer in five different postures. Few papers such as Groenesteijn et al. [6] compare the backrest angle for different chairs and for different activities, giving information as to which is more comfortable in relation to the tasks performed. ...
It is envisioned that the development of fully autonomous driving technology would allow future drivers to participate/engage in secondary activities other than the driving task. To undertake these non-driving secondary activities, the driver would need to be seated in a position that is different to the conventional driving position. In this study, a survey of scientific literature in the field of the relevant secondary activities, the associated seating positions, seating and body angles are being conducted by referring to 18 different sources published up to 2017. The aim of this study is to find out commonly used seat angles for different secondary activities and their seating positions. There is a current lack of literature specifically for seating positions of non-driving secondary activities, hence the research field was extended to consider a range of similar seating including office chairs, passenger seats in trains and aircraft, massage chairs, and lounge chairs among others.
... According to research, individuals whose mobility depends on wheelchairs, particularly spinal cord injury (SCI) patients, spend 10.6 h per day in wheelchairs (Sonenblum et al., 2008). The cushioning and shape of a seat are important factors for comfort during long -duration tasks (Groenesteijn et al., 2009). Sustained mechanical loading, such as pressure, causes pressure ulcers over a bony prominence (Oomens et al., 2015). ...
... Objective measurements are used to obtain quality values that can indirectly indicate subjects' physical functionality and comfort. Such methods include electromyography (Andersson and Ortengren, 1974;Gregory et al., 2006;Kingma and van Dieen, 2009;Van Dieen et al., 2001), magnetic resonance imaging (Baumgartner et al., 2012;Fryer et al., 2010;Zemp et al., 2013;Sonenblum et al., 2013), and pressure distribution measurements of the seat pan and backrest (Carcone and Keir, 2007;Groenesteijn et al., 2009;Gil-Agudo et al., 2009), and heart rate variability measurement (Le and Marras, 2016;Weston et al., 2017). Measuring the pressure distribution of the seat pan and backrest is one of the most common objective methods for analyzing and comparing chairs and sitting positions (Zemp et al., 2016). ...
... A comfortable seat interface plays an essential role in the design of chairs and cushions. Cushion and seat designs affect the pressure distribution at the subject-specific interface, and 'ischial' pressure is linearly related to seat comfort (Groenesteijn et al., 2009;Ebe and Griffin, 2001). As more jobs must be performed in a sitting posture, comfortable chairs are needed because uncomfortable seats reduce work productivity. ...
Sitting is the most common posture for work in offices, and spinal cord injury (SCI) patients who are wheelchair dependent spend 10.6 h per day seated in wheelchairs. Thus, the comfort of subject-specific interfaces is increasingly important for the well-being of patients and office workers. This paper introduces a new method of forming a subject-specific interface, based on vibrating grains. Twenty subjects (10 females and 10 males) participated in the sitting test. Interface comfort was evaluated using the pressure distribution and subjective rating methods. Five seating interface types were compared. The results showed that compared with a flat interface, the interfaces formed by vibrating grains had a significantly reduced peak contact pressure (PeakCP) (by more than 58.03%), and that PeakCP was highly correlated with the comfort rating (R = -0.533) and discomfort rating(R = -0.603). This new method shows promise for guiding the future development of customized seating interfaces.
... Many studies use discomfort recordings to check the effect of an intervention [10][11][12]. For instance, Groenesteijn et al. [11] used questionnaires on local postural discomfort to determine the difference in experience between two chairs. ...
... Many studies use discomfort recordings to check the effect of an intervention [10][11][12]. For instance, Groenesteijn et al. [11] used questionnaires on local postural discomfort to determine the difference in experience between two chairs. Reducing discomfort is not a luxury. ...
... In theory, a difference in discomfort found in several of the 318 studies (e.g. [11,12]) may be attributed to the way the measurement of discomfort was performed. For instance, the possibility is that a "new situation" recorded in the morning is the "old situation" recorded in the afternoon. ...
A review of literature on comfort and discomfort indicates an increase in physical discomfort during the workday. In this paper, three different types of occupations were studied to identify whether a similar discomfort pattern exists in these occupations while participants perform work throughout the work day and workweek. Results are that sedentary and labor intensive occupations show an increase in physical discomfort throughout the workday. In addition, during the workweek, each occupation had a peak discomfort day and all occupations experienced a reduction of discomfort at the end of the last day of the workweek. Acknowledging and understanding why, when, and where discomfort peaks occur could assist in varying task scheduling to improve job performance. Future research should include emotional and psychological discomfort assessments, investigation of effects of age, time of year, and location in the world are warranted.
... People's demand for high-speed trains has gone beyond functional pragmatism, and more attention has been focused on the comfort and humanistic connotation of the riding environment, such as the CRH380 high-speed train interior environment shown and seats in As the only resting facility that is in contact with passengers' bodies for a long time, the train passenger seat directly affects the comfort of the ride. At present, many researchers have carried out studies on the influence of seat shape, material, height, depth, and other factors on ride comfort, involving aircraft [1][2][3], cars [4,5], office chairs [6], and wheelchairs [7] and other fields. However, high-speed trains are different from cars, motorcycles, offices, and wheelchairs in terms of riding environment, so the evaluation of seat riding comfort should be different [8]. ...
... Among them, the difference between S1 and S4 is in the front-end design of the seat cushion, which is the front-end downward and upper drum types, respectively, and the comfort score of S4 is significantly higher than that of S1 (p<0.05). However, the S1 is the more popular cushion type in office seating [6]. For office conditions, the front of the seat is a desk, and the front is tilted downward to maintain an upright or forwardleaning working posture [30]. ...
In this paper, eight different contoured cushions (S1-S8) in two categories (flat and wrapped) were designed to study the influence of different contoured cushions on passenger comfort in high-speed trains. Meanwhile, subjective data investigation by the comfort Likert Scale questionnaire and objective physical variables collection by the body-cushion contact pressure test was carried out. In addition, one-way ANOVA and Pearson correlation analysis were performed on the subjective survey and objective test data. The results show that the cushion contours had a significant effect on the subjective evaluation of the overall comfort of the participants, in which the overall comfort below the waist of the separated wrapped cushion S8 has the highest subjective comfort score. The overall comfort of the flat-front bulge type cushion S4 and the local comfort of the thighs and the root of the thighs were rated higher than other flat types. Under the flat cushion, the effect of stature characteristics (mainly weight and hip-width) on the overall comfort subjective ratings was insignificant, and the effect on the contact pressure distribution variables was significant, but the contact pressure distribution variables were not correlated with the comfort ratings. Under the wrapped cushion, the effect of stature characteristics on the overall comfort subjective ratings and contact pressure distribution variables was significant. There were positive and negative correlations between the average peak contact pressure and average contact pressure and comfort ratings, respectively.
... As a result, a large number of publications have discussed the negative impacts of applying continuously unrelieved pressure on a person's health ( Table 2). As would be expected, the findings are diverse and include: the average pressure [40][41][42], the centre of force [43], the peak pressure [17,42,44] and the pressure distribution at seat pan and back rest [45][46][47]. In addition to simply quoting the pressure, this parameter has also been used to infer in-chair movement or fidgeting [48]. ...
... To illustrate the characteristics of interface pressure, directly measured data were represented in various parameters, including the mean backrest pressure [44,[78][79][80], the maximal backrest pressure [44], the seat pan contact area [44], the mean seat pan pressure [44], the maximal seat pan pressure [44,46] and maximum and mean buttocks and back support pressure [72]. By converting the measured pressure values into other variables, some researchers investigated the changes at the contact interface using the pressure distribution pattern over time [80], average contact area [67] and ICM [48,73]. ...
Being seated has increasingly pervaded both working and leisure lifestyles, with development of more comfortable seating surfaces dependent on feedback from subjective questionnaires and design aesthetics. As a consequence, research has become focused on how to objectively resolve factors that might underpin comfort and discomfort. This review summarizes objective methods of measuring the microenvironmental changes at the body–seat interface and examines the relationship between objective measurement and subjective sensation. From the perspective of physical parameters, pressure detection accounted for nearly two thirds (37/54) of the publications, followed by microclimatic information (temperature and relative humidity: 18/54): it is to be noted that one article included both microclimate and pressure measurements and was placed into both categories. In fact, accumulated temperature and relative humidity at the body–seat interface have similarly negative effects on prolonged sitting to that of unrelieved pressure. Another interesting finding was the correlation between objective measurement and subjective evaluation; however, the validity of this may be called into question because of the differences in experiment design between studies.
... These studies often use discomfort recordings to check the effect of an intervention. For instance, Groenesteijn et al. (2009) studied the postural discomfort experience to determine the differences between two chairs. ...
... Most scientific studies therefore use within subject designs in conditioned environments to check differences between products. For instance, in the study of Groenesteijn et al. (2009) different seats were used in the same environment with the same participants. ...
In order to investigate differences in comfort and discomfort experiences amongst different regions of the world (America, Asia and Europe), a cross cultural study was performed. A questionnaire was sent to participants out in 9 countries (Brasil, Canada, USA, China, Indonesia, Thailand, Germany, Italy and the Netherlands). In total 795 participants completed the questionnaires. All countries score the comfort of a luxurious bed higher than a simple bed, first class seats higher than economy class and all countries rate the comfort lower when the duration of sitting increases. The study suggests that in the USA and Canada softer beds, hammocks, more luxurious seats and softer pillows are scored as more comfortable compared with the other countries. There are indications that China and Germany prefer a harder mattress then in the other countries. For pillows the differences between countries are large, which might show that much is influenced by habitude or hesitation to use something new. The Asian countries score the comfort of a brace neck pillow higher, which might be because these participants better realize the benefits better or feel less concerned to wear something that might give the appearance of an orthotic device. Further studies are needed to confirm these suggestions. The study shows that obvious differences are seen in all countries, which makes the construct of comfort internationally comparable.
Practitioner summary: In designing and manufacturing globally it is important to know how different parts of the world experience (dis)comfort. This study did not show large cultural differences amongst nine countries. Some differences emerge regarding pillows, perhaps as differences in sleeping habits play a role. Keywords: comfort, discomfort, cross cultural, different countries, sitting, sleeping
... Nor is the busy office worker likely to prioritize studying the 42-page chair user guide reported by Vink et al. (2007). Groenesteijn et al. (2009b) suggested that most users do not invest effort in learning their chair's adjustable functions. Results of a Dutch-Spanish office chair field study by Vink et al. (2007) showed that 24% of 246 Spanish office workers and 61% of 100 Dutch office workers had never adjusted their chair. ...
... The most prevalent reason for previous chair adjustment was 'To make my body more comfortable' (77%). Although Groenesteijn et al. (2009b) questioned whether some users fail to link their discomfort to their chair settings, this study's results suggest that optimising comfort drives at least some chair adjustment behaviour. Although reasons for previous chair adjustment were not categorized within physical, cognitive and organizational ergonomics domains (IEA, 2018) in this study, the five most prevalent related to users' perceived physical needs such as a desire 'to reduce pain in my body', 'make my body more comfortable' or 'change my posture' (see Fig. 2). ...
A quantitative field study measured end-user availability, knowledge and use levels of adjustable office chair functions in Korea-based office workers, together with their perceived barriers towards making adjustments. Fifty-one English-speaking workers were interviewed and surveyed in a related design. Results showed that of the number of adjustable functions available on their office chair (M=5.39, SD=2.3), participants knew fewer than half of them (M=2.51, SD=1.52) and used even less (M=1.86, SD=1.21). Fifty-three percent of participants knew two or less and 73% had used only two or less. Ten percent had used none. Results suggested physical needs (such as increased comfort or postural change) were a strong driver for previous chair adjustment behaviour. Perceived cognitive barriers played a more significant role in limiting chair adjustment knowledge and use than physical or organizational barriers. Highly adjustable office chairs have the possibility of satisfying the adjustment needs of most end-users. However, adjustable chair functions need to be both available and known in order to be used.
... Testing was conducted in a laboratory of the faculty of Engineering at the University of Salerno. Thermal conditions were measured and controlled in order to avoid any influence on (dis)comfort perceptions [29]. Subjects were asked to sit at the workstation and to simulate the usage of the four devices, each one had to give a score on the expected comfort about the workstation itself. ...
... An improvement solution can be easy developed through the use of fully adjustable seats that can allow the subjects to fit to the imposed layout of the fixed table and to choose their best posture in relation to the office-device they want to use and to their anthropometric characteristics. As shown in [29], the control plays a keyrole both in comfort perception and in expectation, thus, the most comfortable office layout will be the one that can be adjusted as people want. ...
Computer aided technologies (CAT) are becoming an indispensable instrument to design, improve and manufacture new products and services. Digital human modelling (DHM) systems allow to simulate the Human-artifact interface and to evaluate, in early step of design process, the ergonomic performances of new products or workplaces. In particular, for products that have to be used in a “constrained” workplace, different tasks and activities are associated with different postures. The aim of this study is to investigate the influence of anthropometric characteristics and expectations on the postural comfort perception through the CAT/DHM systems, while using four office devices: desktop computer, laptop computer, tablet and smartphone. A statistical sample of healthy students was selected and their anthropometric characteristics were measured. The postures assumed by the participants were gathered in a not-invasive way by cameras. The angular detection was performed directly on snapshots by using Kinovea® software. Human joints’ an-gles were used for the virtual-postural analysis, through DELMIA® software. The evaluation of postural comfort was obtained in two ways: CaMAN® software developed by the researchers from the Department of Industrial Engineering in Salerno (Italy) was used to calculate the objective comfort indexes while an appropriate questionnaire, given to subjects during the devices usage, was used to evaluate the subjective com-fort indexes. The results of analyses show a difference between subjective and objective postural comfort indexes for all the devices: this difference has been associated to the expectations.
... Solutions to these are generally proposed but lack the heeling effect and ignorance for the static posture concept. [5] Many constraints about body movements and awkward postures have been discussed off. Deep analysis on chair ergonomics areparallel being carried day often. ...
... This refers to the initial concept of chair design. [6] LiesbethGroenesteijn , Peter Vink , Michiel de Looze , Frank Krause [5] in their studies have focussed on some vivid dimensions of chair study , they have looked upon different chair characteristics . They concluded chairs vary in matter of differentseat cushioning and shape , backrest angle and usability of controls. ...
... De-Looze et al., (2003) determined that the pressure distribution at the pan of the car's chair related to subjective ratings of comfort/discomfort. Also, Groenesteijn et al., (2009) and Vergara and Page, (2000) conducted studies concerning office chairs, and they found a relationship between pressure distribution and comfort/discomfort assessment. Helander, (2003) states that comfort and discomfort are distinct identities accompanying various predisposing issues. ...
Background: Adequate chair design and comfort are essential to the educational environment. Aim: The current study investigated the effect of cushion characteristics on student comfort during class time, aiming to increase the students' comfort and positively affect their academic gain. Material and methods: Thirty-nine volunteer female students participated in this study. Two types of foam were used; the first type was characterized by a density of 25kg/m3, hard, and elasticity of 80.15 N/cm2. The second type was characterized by a 26kg/m3 density, softness, and elasticity of 26.081 N/cm2.The dimensions used for the cushions of both types of foam were 40cm*40cm for both the seat pan cushion and back support cushion, a thickness of 8 cm for the seat pane cushion, and 4cm for the back support. The body part discomfort scale and Comfort and discomfort scale were used for assessment after using the cushions for one and a half hours. Results: The results revealed that general comfort and body part comfort were not different when comparing both cushions. On the other hand, the intensity of pain in the body part discomfort significantly increased when using hard cushioning. Conclusion: Cushion hardness did not affect the subjective sensation of comfort and discomfort, while a hard cushion may cause pain in certain body parts during use.
... Harrison et al. (1999) describes 120 • as the best option for reducing muscle activity and disc pressure, though 130 • increases muscle activity (Harrison et al., 1999). Groenesteijn et al. (2009) found 120 • to be the optimal angle for reading and computing. When 79 men and women were allowed to self-select optimal recline angle for reading or computing in an office setting, the preferred position averaged 115 • (Gscheidle and Reed 2004b). ...
... The study of backrest inclination must consider passenger activity and corresponding postures (Groenesteijn et al., 2009;Liu et al., 2021;Zhong et al., 2022). In the alert state, a relatively upright posture is preferred. ...
... However, most modern office chairs are still far from meeting the above guidelines (Groenesteijna, Vinka, de Loozea, & Krause, 2009). ...
Workplace design deals with the shape, the dimensions, and the layout of the different material elements that surround one or more working persons. In addition, as modern work, particularly in offices, is becoming increasingly collaborative and creative, workplace design should focus on creating a sense of community that enables innovation, encourages new ways of working and nurtures employee well-being. This chapter presents a methodological; and discusses a number of methods, techniques, guidelines, and typical design solutions which aim to support the decisions to be taken during the workplace design process. It examines the problem of working postures and stresses the fact that there is no one best posture which can be assumed for long periods of time. Besides the problem of lumbar kyphosis, working in a sitting posture may provoke excessive muscle strain at the level of the back and the shoulders.
... Hakim and Mohsen (2017) reported that seat discomfort was strongly linked to low back pain in drivers. Groenesteijn et al. (2009) investigated the effect of geometrical parameters of chairs on the comfort level of the Dutch and European standards based on two chair designs. Bressel et al. (2009) conducted a study to investigate the effect of seat pressure of three different seats on cyclists. ...
... It is also found out that there was no difference between comfortable and uncomfortable seat pan, first impressions as well as maximum interface pressure. [12] conducted research on ergonomics study of seated human by using static contact sensors and questionnaires. The study was to investigate the interface pressure distribution and time utilized for chair adjustment. ...
Chair comes in different sizes and shapes depending on the functions as well as the users involved. However, the designers seldom consider the ergonomics aspect in chair design. This research has been conducted as a case study to compare and select the best design parameters within two chairs known as Chair A and B using human modelling software called AnyBody. Different parameter was manipulated in the simulation which is backrest angles for Chair A and seat heights for Chair B. A total of ten chairs with different parameters (five from Chair A and five from Chair B) were conducted in the simulation. Results were generated through inverse dynamics analysis in the form of muscle activities envelopes and reaction force on vertebrae L4 to L5. The result shows that 80° backrest was the best ergonomics design for Chair A while 0.30 m seat height was the best ergonomics design for Chair B. The simulation conducted is important as an early ergonomics intervention before the real chair fabrication is conducted.
... To our knowledge, there are no studies investigate the characteristics of whole-body regions while seated and sedentary workers' stress conditions in screen-based ofce working scenarios. Considering the strong association between tasks requirements and posture [9,14], the role of how diferent computing-based tasks play on ofce workers' sitting behavior and how the stress states and tasks intertwined with sitting behavioral shifts are rather under-explored. This study aims to fll the gap by empirically exploring the impact of stress on sedentary workers' sitting behavior during screenbased computing tasks. ...
... Horton et al. (2010) explained that an angle of 110 degrees, and backrest, are essential to the modelling of a chair as it affects the posture of the neck or head. (Groenesteijn et al., 2009) made known the significance of a chair property such as seat, control, backrest angle, and posture relative to an activity performed. The provision of lumbar support (adjustable) seems to be preferred by people due to the differences in body features. ...
... Therefore, it is essential to have a seat back that minimizes the spinal loading and relax the back muscles of the user. Such minimization and relaxation can be best achieved with a backrest inclined backwards [12,13]. Chaffin et al. found that the stress on the spinal discs can be reduced approximately 40% by reclining the chair 20° degrees [14]. ...
Sit-to-stand is regarded as one of the most mechanically demanding daily tasks. Because of body weakness or disability of some Muslims, they cannot assume all the required physical motions of prayers without relying on a conventional chair. However, using a conventional chair when praying in mosques may lead to two main problems: (1) Disturbing the worshipers in the row behind the chair and/or (2) causing the user of the chair to be misaligned with the row of prayer. In the present paper, a novel conceptual design for a congregational prayer chair that alleviates such disturbances and misalignment problems is addressed. First of all, the existing causes and patterns of using conventional chairs while praying in mosques are outlined. Secondly, design criteria for congregational prayer chairs are established. After that, a novel conceptual design for a congregational prayer chair is explained. The obtained results identified 15 existing causes and 18 patterns of using chairs while praying and 2 patterns of chair placement in the row of prayer. In addition, the results show that the most praying position chairs are used for prostration. This study reveals a key feature concept considered in the conceptual design of the chair to solve the aforementioned problems through constructing a predetermined moving seat pan and a seat back so that the user can attain whatever praying positions without changing the placement of the chair.
... In [24] backrest and seat pan pressure have been measured by means of a X236 capacitive pressure-sensing system, by Xsensor Technology Corporation, consisting of two 46 cm×46 cm element arrays [25]. In [26] the contact pressure between chair seat and buttock was measured by means of a Novel Pliance-x system, which consist of a flexible and elastic measuring sensor mat, a multi-channel analyser, a calibration device and a software package for PC [27]. A commercial solution for the measurement of pressure distribution has also been used in [28], where authors adopted a FSA Force Sensing Applications pressure mapping system by VERG Inc [29]. ...
... To bring this advancement into action the commonest adjustable feature added among office chairs was an "adjustable knob" underneath the seat by means of which any individual could adjust the height of the seat and degree angle to support the lower and upper back according to his overall height, leg length for a comfortable and ergonomic sitting. But, in few instances either these features are not explained to all individuals when deployed or individuals do not give importance to the adjustment to be made in the chair according to their personal body structures, hence making them devoid of using the office chairs in the optimal ergonomic manner [2]. This noneffective use of office chair in combination with the actual daily use of these chairs lead to development of faulty postures by using them during office hours which the individuals maintain without knowledge and hence predisposes self to problems like thoracic kyphosis, forward head syndrome, cervical radiculopathy, elbow stiffness, carpal tunnel syndrome, flat back, pain in buttock and sciatica [3]. ...
Since the introduction of the parameters and guidelines for office chairs, great effort has been put while designing, manufacturing and assembling well equipped ergonomic office chairs. Designing of these office chairs led to many new additions and advancements of various major components like the seat height, adjustable back rest and adequate thigh support. So, this study was planned and executed to check the usage of ergonomic office chairs by the faculty members and the prevalence of pain in various areas and joints among male faculty members under different colleges of Jazan University. Total of 150 male faculty members from different colleges under Jazan University participated in this study. All individuals have explained the need for the current study and their consent was taken. The data were collected from all the subjects and complied which was put for statistical analysis. The result after analysis showed the prevalence of pain in lower back in 63 subjects (42%) followed by pain in upper back for 37 subjects (24.67%), shoulder pain in 17 subjects (11.33%), buttock pain in 15 subjects (10%), elbow pain in 9 subject (6%), pain behind thighs in 5 subjects (3.33%), knee pain in 4 subjects only (02.67%) and no non-subject expressed pain in wrists, fingers and ankles as their prior most discomfort.
... Another work of Horton et al. [9] described that the angulation and back rest support is equally important in chair design as it infuences the head and neck posture. Groenesteijn et al. [10] showed the impact of chair characteristics like chair control, seat, back rest angle on human behaviour, and posture depending on the task they perform. According to Coleman et al. [11] the adjustable lumber support is more preferable for the users because of the difference in physical characteristics. ...
The world of ergonomic evaluation considerate the human biomechanics and anthropometric measurement an integral part of product design and development work. In this paper, we have given an attempt to design an ergonomically fitted office chair suitable for Bangladeshi people. In this paper, the anthropometric data analysis has been done in order to determine the necessary dimensions suitable for the office chair. Lastly, an ergonomically fitted office chair is designed based on this anthropometric data analysis. The concept of the paper is to focus on the dimensional changes that the Bangladeshi people need for their comfort in the ergonomic office chair. The structural difference in different regions makes us inspired to think about the office chair ergonomics for Bangladeshi people. In short, this paper reflects the entire process of designing an ergonomic office chair suitable for them.
... Further test would be pairing the assessment tool with objective measures in both static and dynamic environment to examine the correlation between them. Groenesteijn et al. (2009) Investigate the influence of chair characteristics on comfort, discomfort, adjustment time and seat interface pressure No significant differences found for seat design comfort and discomfort, first impression and peak interface pressure. ...
One of the key considerations when sitting particularly for a long period of time, either in the office chair or car seat is comfort. Studies have revealed a high number of reports regarding discomfort and musculoskeletal disorders while sitting in a fixed position. The main objective of this study is to review past and present subjective assessment in published studies in the area of sitting discomfort and find the gap between each study to be applied in future studies. Fifty relevant studies were identified and chosen from electronic databases, dating as far back as 1969. "Seat", "chair", "sit", "comfort", "discomfort" and "assessment" were the keyword search terms for this paper. Past studies demonstrated numerous purposes and techniques of analysing sitting discomfort. They provide better understanding for both researchers and the industry to deal with sitting discomfort issues. Various assessment methods have also been applied in the previous studies. However, they are still areas found in past studies that need to be investigated. Therefore, it is proposed that another assessment is performed to analyse sitting discomfort, by exploring issues derived from this review.
... Consequently, a dynamic office chair should be fitted with a backrest. Office chairs with an adjustable seat and backrest usually allow axial rotation (horizontal plane) and backwards tilting (sagittal plane) (Ellegast et al., 2012;Groenesteijn et al., 2009). Tilting backwards facilitates the relaxation of the back muscles, relieves load on the spine, and increases the trunk thigh angle (Pope et al., 2002;Van Dieen et al., 2001;Vergara and Page, 2002;Bush and Hubbard, 2008;Harrison et al., 1999). ...
Objective: This study investigated the location of the axis of rotation in sagittal plane
movement of the spine in a free sitting condition to adjust the kinematics of a mobile seat for a dynamic chair.
Background: Dynamic office chairs are designed to avoid continuous isometric muscle
activity, and to facilitate increased mobility of the back during sitting. However, these chairs incorporate increased upper body movement which could distract office workers from the performance of their tasks. A chair with an axis of rotation above the seat would facilitate a stable upper back during movements of the lower back. The selection of a natural kinematic pattern is of high importance in order to match the properties of the spine.
Method: Twenty-one participants performed four cycles of flexion and extension of the spine during an upper arm hang on parallel bars. The location of the axis of rotation relative to the seat was estimated using infrared cameras and reflective skin markers.
Results: The median axis of rotation across all participants was located 36cm above the seat for the complete movement and 39cm for both the flexion and extension phases, each with an interquartile range of 20cm.
Conclusion: There was no significant effect of the movement direction on the location of the axis of rotation and only a weak, non-significant correlation between body height and the location of the axis of rotation. Individual movement patterns explained the majority of the variance.
... Tullis and Albert (2008) noted that the parameter "time-on-task" could be used for the usability evaluation of various products and stated that the shorter the task time, the better is the experience. In addition, Groenesteijn et al. (2009) reported that user satisfaction was high when the task time required for making some adjustments to the armrest position, backrest reclining position, and weight resistance of office chairs was short. However, for the usability evaluation of products whose adjustment requires more complex steps, it is important to simultaneously analyze the results of the task execution time and the step-by-step procedure. ...
In this study, foldable bicycles were evaluated in terms of their usability. Four types of folding mechanisms were identified depending on the number of pivots and the pivot axis direction: single lateral pivot (SLP), single vertical pivot, dual lateral pivot, and combined vertical-lateral pivot. Next, four bicycles-one each of these four types-were selected as test specimens. Ten subjects performed folding and unfolding tasks on each of these bicycles, and three-dimensional body motions and ground reaction forces were measured. The maximum trunk flexion angles and maximum increments in the ground reaction force were used as governing parameters for evaluating the comfort level for each bicycle type. The SLP type provided the lowest upper body flexion and ground reaction force and was hence judged to be the most comfortable folding system. Hence, a promising type of easily foldable bicycle was proposed, thereby encouraging its incorporation into public transit systems.
... Harrison et al. [21] expressed the best option for reducing muscle activity at the back is at 120° backrest inclination and they also found that an inclination angle of 130° resulted in more back muscle activity. Recently, Groenesteijn et al. [22] suggested that, 120° backrest inclination is the optimal angle for computing and reading in a computer monitor. On the whole, in order to reduce loading on the spine of users, the backrest angle is in the range of 90-120° [23.] ...
In order to facilitate the advancement of computer based technology and prevent health risk associated with computer workstations (non-ergonomics), a modification of the computer workstations is essential. The ergonomics for design of computer workstations leads to motivate the work, higher performance, efficiency and quality of work. Current scenario, our society spends lot of time with computers, thus the computer workstation needs to provide comfort to users. Discomfort position can harmfully affect the overall health and performance of work. In this past, present and future trends of computer workstation designs are discussed. Furthermore this paper offers the suggestions for design of computer workstations and simple exercises to reduce musculoskeletal disorders of prolong time users.
... Pressure distribution appears to be the objective measure with the most clear association with the subjective comfort and discomfort ratings (De Looze et al., 2003). These studies (Fujimaki and Mitsuya, 2002;Groenesteijn et al., 2009;Vergara and Page, 2000) analyzed that discomfort reported a relationship with pressure parameters, whereas one study (Carcone and Keir, 2007) could not find a relation between discomfort and pressure measurements. Pressures have been used in the evaluation of car seats Milivojevich et al., 2000;Zenk et al., 2012), wheelchairs Geyer et al., 2001;Shaw, 1993) and workstation (Fujimaki and Mitsuya, 2002), for which comfort and function are very important. ...
The objective of this work is to analyze the effect of long-duration sitting on a seat with the limited space on discomfort, body flexibility and surface pressure, and the changes of discomfort, surface pressure and body flexibility with the sitting time. The experiment was that eighteen healthy subjects seated for long-duration (3 h) in three different seat pitches (32 inches, 30 inches and 28 inches) conditions in the laboratory. The discomfort, pressure, and body flexibility parameters have been measured during the experiments. Comparing the data between three seat conditions during the sitting time, the results show that there is a significant difference in the overall discomfort ratings and pressure variances between three different seat conditions after 3 h, and significant effects were found among the three different seat pitches for the discomfort rating of shoulder, middle back and low back after 3 h. No significant findings were seen in lumbar and hamstring flexibility. The relationship between subjective ratings and objective measurements has been analyzed with spearman analysis. The correlation analysis suggest that differences in arm and middle back discomfort were significantly negatively correlated to Sit-Reach(3) scores (Correlation Coefficients: 0.492 and −0.527; p values of 0.038 and 0.025, respectively). Differences in overall discomfort, thigh and knee were significantly correlated to average pressure (Correlation Coefficients: 0.562, 0.833 and 0.520; p values of 0.004, 0.001.and 0.027, respectively).
The importance of ergonomics design cannot be over emphasized, as non-ergonomics designs can lead to musculoskeletal disorder. This research is aim at determining the optimum seat height that will be best for humans putting into consideration height, weight, age and sex.
All relevant parameters were taken into consideration during the research. The research was conducted in a control environment for accurate results, and the results and findings will be invaluable in the design of ergonomics chairs.
Our goal in this research paper, is to determine the optimum seat height for college students, using subjective (comfort) assessments. This finding will help designers and practitioners to choose an appropriate anthropometric criterion for either designing a seat height or evaluating match/mismatch.
Chair design features are typically compared using multiple seats, which can lead to confounding effects. Using a single chair, configurable to four designs (control, lumbar support, seat pan tilt and scapular relief), we investigated the effect of chair design on spine posture and movement, muscle activity and perceived pain in a sample of 31 asymptomatic adults. A total of 39% of the population were classified as pain developers, having significantly higher peak pain levels across most body regions. The lumbar support and seat pan tilt condition resulted in more neutral spine and pelvic postures. Greater muscle activity was found in the seat pan condition and non-pain developers displayed lower spine muscle activation levels overall. Despite some improvements in spine posture, sitting-induced pain was present in the study sample at similar proportions to those reported previously. Future studies may consider investigating interventions targeted to sitting-induced pain developers as opposed to the general population.
Practitioner summary: Four office chair configurations were tested. The lumbar support and seat pan tilt conditions resulted in the most neutral back posture but did not mitigate the clinically significant levels of sitting-induced pain experienced by a large portion of the tested sample. Future work should target interventions to these individuals.
The joint angles of three most common postures of passengers sitting in the rear seats (sleeping, standard, upright) were recorded to develop an ideal posture model for rear seat passengers within a car. The passengers were positioned in a realistic mock-up of a whole car interior with a fully adjustable back seat and postures recorded. The results showed that the upright and standard postures have similarities to the postures of the driver’s seat in the literature. The relaxed posture showed a higher angle between trunk and thigh compared with the driving position and the variation in leg postures was much larger, which can be explained by the fact that the legs have more freedom in the rear seat than in the driving position.
Chair comes in different sizes and shapes depending on the functions as well as the users involved. However, the designers seldom consider the ergonomics aspect in chair design. This research has been conducted as a case study to compare and select the best design parameters within two chairs known as Chair A and B using human modelling software called AnyBody. Different parameter was manipulated in the simulation which is backrest angles for Chair A and seat heights for Chair B. A total of ten chairs with different parameters (five from Chair A and five from Chair B) were conducted in the simulation. Results were generated through inverse dynamics analysis in the form of muscle activities envelopes and reaction force on vertebrae L4 to L5. The result shows that 80° backrest was the best ergonomics design for Chair A while 0.30 m seat height was the best ergonomics design for Chair B. The simulation conducted is important as an early ergonomics intervention before the real chair fabrication is conducted.
The main purpose of this research is to determine the impact of chair ergonomics, posture, and long-term sitting on employee productivity. Furthermore, the paper addresses the relationship between workplace ergonomics, prolonged and continuous sitting, employee burnout, and employee health. A structured survey was used to evaluate employees in manufacturing and service industries. The obtained data was analyzed with reliability statistics, regression analysis, and correlation analysis. The results are interesting, and contradict the majority of the existing findings in this domain. Even though there are limitations, this current study addresses work environment ergonomics in a concise way, providing significant and unexpected results.KeywordsWorkplace ergonomicsEmployee productivitySedentary jobs
Although improving customer satisfaction, driving safety, and the appearance, exterior, and interior design of customers is crucial, detailed investigations regarding comfort in operating levers to adjust a seat are not available. The design and alignment of car seats and levers have various constraints owing to the limited availability of space. Thus, this study aimed to determine the best lever position considering various constraints of vehicles, including safety, space, operability, and anthropometric variability. Subsequently, a relationship with the Kansei score for various classes of participants, such as low-torque occupants (female and elderly) and high-torque occupants (male), and users with a wide range of height was determined. This study involved a Kansei assessment (SD method) based on five Kansei scores selected from a preliminary survey. The lever positions (height/horizontal distance) evaluated in this experiment were found to be suitable for vehicle designs under severe constraints. ANOVA analyzed the Kansei scores by gender and showed a statistically significant difference (P < 0.1). The results showed that places with good Kansei scores for females were mainly in the high Kansei area of males (average of 3.0 or more). Females' high Kansei score areas were smaller and located within the Kansei areas of males. Meanwhile, males' lowly evaluated (average value: −1 σ or less) area was smaller and located within the Kansei areas of females. The relationship between subjects’ height and Kansei were analyzed with linear and quadratic regressions. The distribution of the Kansei score on lever positions was graphically analyzed using LOESS nonlinear local regression. Acceptable lever positions were shown by LOESS. Finally, a statistical learning method, CART (Classification and Regression Tree) + Random Forest, was used to generate rule chains for the lever position specificity and anthropometric profiles. The results were in good agreement with the analyzed results obtained using traditional methods. To achieve safety in a collision accident and comfort at regular times in a narrow space of a vehicle interior, the parameters for lever positioning with respect to ease of operation were discussed for the findings in product development.
In the current situation of covid-19 pandemic, the supply and demand relationship of medical resources in various hospitals is unstable. However, people's needs for understanding their health status are increasing. The purpose of this project is to assist telemedicine so that people can check their health at home. So, we proposed a civilian medical furniture solution. In the solution, we took the chair design as an example. First, we found out the user’s needs and pain points via observation and interview. Based on this, we analyzed the characteristics of chair design and developed a prototype using a flexible contact sensor technology. In a follow-up evaluation experiment, we also added the details of the product according to ergonomic design principles of sitting posture. Moreover, after obtaining the heath data of users, we improved the product quality by visualizing the data. Finally, we tested the interactive effects of data visualization and then received positive feedback from users. The results of this project could help the design and development of civilian medical furniture.
Once an ergonomic office chair is purchased in the workplace, it usually remains in circulation far beyond its acceptable life cycle and warranty. Older chairs present ergonomic and safety risks exposing employees to unnecessary musculoskeletal stress and strain resulting in injury exposure claims for the employer. This paper introduces a chair assessment methodology using predictive analytics to evaluate the quality and competency of an office ergonomic chair over time. Rather than relying solely on an employee’s subjective, biased opinion of chair quality or waiting for absolute failure; instead an objective, measurable rating scale is used to determine chair status. The Chair Assessment (software) System (CAS) provides an overall score indicating whether the chair should remain in use, be repaired or removed from circulation in a timely manner so it can be replaced. The Chair Assessment System is part of a furniture asset management system focused specifically on chair use-life cycle.
The majority of work-related musculoskeletal disorders (WRMDs)in surgery are mostly related to sustained position and awkwardpostures, forcing non-natural gestures in surgeon ́s body.This arti-cle points to describe the different ailments studied during surgicaltasks over the years: causes which increase the discomfort andfatigue, and effects related with them, in order highlight the cur-rent working conditions and how might be improved. To do that,a research is done to understand the main issues related on fullbody ailments and how is have been evaluated in different typesof surgery, for which, the lead postural analysis technologies arepresented, understanding Rapid Upper Limb Assessment system(RULA) the most suitable method to stablish priorities for preven-tive/corrective actions.Knowing the ailment ́s causes it have beennecessary to define the critical points related with the causes, asinstrumentation design, regulations in operating tables and chairs,pedal drives, and other surgical elements that require a ergonomicimprovements, so that, the main design guidelines have been col-lected in this document and have been compared with a sampleof current products available in the market, with the purpose ofknowing the degree of implication between the requirements re-quested by the surgical teams and the companies dedicated to theirdesigns.
The majority of work-related musculoskeletal disorders (WRMDs)in surgery are mostly related to sustained position and awkwardpostures, forcing non-natural gestures in surgeon ́s body.This arti-cle points to describe the different ailments studied during surgicaltasks over the years: causes which increase the discomfort andfatigue, and effects related with them, in order highlight the cur-rent working conditions and how might be improved. To do that,a research is done to understand the main issues related on fullbody ailments and how is have been evaluated in different typesof surgery, for which, the lead postural analysis technologies arepresented, understanding Rapid Upper Limb Assessment system(RULA) the most suitable method to stablish priorities for preven-tive/corrective actions.Knowing the ailment ́s causes it have beennecessary to define the critical points related with the causes, asinstrumentation design, regulations in operating tables and chairs,pedal drives, and other surgical elements that require a ergonomicimprovements, so that, the main design guidelines have been col-lected in this document and have been compared with a sampleof current products available in the market, with the purpose ofknowing the degree of implication between the requirements re-quested by the surgical teams and the companies dedicated to theirdesigns.
Seat pitch, defined as the distance from a point on the back of one seat to the same point on the seat in front, is one of the most important factors influencing aircraft seating comfort. This study assessed the influence of different airline seat pitches on subjective ratings of discomfort and body-seat interface contact pressures. This was a laboratory within-subjects study using an aircraft interior mock up to vary seat pitch. Twelve participants completed 1 h of sitting in each of five different seat pitches (28inches, 30inches, 32inches, 34inches, and 36inches). Interface pressure mats measured seat and backrest pressure distribution, subjective rating scales were used to measure overall and local body region discomfort. The results showed that overall body and local body region discomfort ratings tend to be lower when the seat pitch increased from 28 inches to 36 inches (p < 0.05). For pressure variables, the upper back average contact area, upper/lower back average contact pressure, upper/lower back average peak contact pressure, right buttock average contact area, left/right thigh buttock average peak contact pressure, and left buttock average peak contact pressure were significantly affected by seat pitch(p < 0.05). Separate analyses support that seat pitch was more strongly correlated with backrest interface pressure than with seat pan pressure. In conclusion, seat pitch was found to be an important factor associated with body-seat contact pressure and discomfort ratings.
This paper focuses on the comparative assessment of comfort and discomfort (hereafter, (dis-)comfort) for aircraft seating. Subjective and objective data of seating (dis-)comfort were collected during an experiment involving 20 volunteers who tested 3 aircraft double-seats in upright and reclined position. In order to minimize experimental uncertainty due to well-known noise factors (i.e. patterns of discomfort during the work week and during the work day, order of evaluation, inter-individual differences), experimental trials were performed according to a crossover design. Statistical data analysis aimed mainly at investigating (dis-)comfort differences across seat conditions; gender-based differences in perceived discomfort on different body parts; effect of sitting duration on perceived discomfort on different body parts. The experimental results show that differences across seat conditions impacted differently on perceived discomfort depending on gender, body parts and sitting duration. No significant differences in perceived discomfort across gender were evident for the lightweight seat in both upright and reclined positions. On the contrary, for both baseline configurations, perceived discomfort at head and neck areas was higher for males than for females. For all seat conditions, participants experienced a significant worsening of perceived comfort over time at shoulders, back, sacrum and thighs and, in addition, at upper body area (i.e. neck, arm and forearm) and knees only for seats in reclined position.
Potential alternatives for conventional sitting and standing postures are hybrid sit-stand postures (i.e., perching). The purposes of this study were i) to identify where lumbopelvic and pelvic angles deviate from sitting and standing and ii) to use these breakpoints to define three distinct postural phases: sitting, perching, and standing, in order to examine differences in muscle activations and ground reaction forces between phases. Twenty-four participants completed 19 one-minute static trials, from sitting (90°) to standing (180°), sequentially in 5°trunk-thigh angle increments. The perching phase was determined to be 145–175° for males and 160–175° for females. For both sexes, knee extensor activity was lower in standing compared to perching or sitting (p < 0.01). Anterior-posterior forces were the highest in perching (p < 0.001), requiring approximately 15% of body-weight. Chair designs aimed at reducing the lower limb demands within 115–170° trunk-thigh angle may improve the feasibility of sustaining the perched posture.
Practitioner Summary: Individuals who develop low back pain in sitting or standing may benefit from hybrid sit-stand postures (perching), yet kinematic and kinetic changes associated with these postures have not been investigated. Perching can improve lumbar posture at a cost of increased lower limb demands, suggesting potential avenues for chair design improvement.
Extensive research has been performed on ergonomic chair design and the impact chair design has on seated posture and the musculoskeletal system of office workers. The research has significantly advanced the science of sitting and the design of office ergonomic chairs. BIFMA and ANSI criteria have identified guidelines for manufactures and consumers to better understand the features an office ergonomic chair should possess. There is a gap in the literature, however regarding how to assess the ongoing performance of an ergonomic chair after it is placed into the workplace. Not as it applies to the fit to the end-user, but the quality and competency of the chair to remain in use in the workplace. Once an ergonomic office chair is purchased in the workplace, it often remains in circulation far beyond its acceptable life cycle and warranty. As a result, chairs that are old, worn, outdated and inoperable continue to be used by office workers. These older chairs often present additional ergonomic and safety risk factors exposing employees to unnecessary musculoskeletal stress and strain resulting in injury exposure claims for the employer.
Office workers are at high-risk for work-related musculoskeletal disorders (WMSDs), which can inhibit productivity and perceived comfort through associated disorders (Piligian et al, 2000). An increase in WMSDs has created a demand for ergonomic office interventions. Recent ergonomic advancements have focused on dynamic office furniture that aim to promote chairs featuring structural designs (Ellegast et al, 2012). Dynamic office furniture lacking a range of specific and modifiable adjustments can lead to adverse outcomes, such as nerve compression, resulting in perceived discomfort and increased risk of musculoskeletal disorders (Groenesteijn et al, 2009; Legg et al, 2002). However, there is limited research regarding the relationship of posture changes and the effects on perceived comfort and task performance. The objective of the study was to explore the relationship between perceived comfort, productivity, postural changes, and adjustability in chairs with varying degrees of adjustability. The study consisted of 44 participants (54.5% males, 22.8 (2.89) years) attending three different days, working together in teams of 2-3, to complete a 3-hour simulated office task related to construction science. Tasks required team collaboration to evaluate construction bids, develop plan of actions, and present conclusions to each task. To determine the ergonomic impact of office furniture on team creativity and productivity on the design project, two different types of chairs were employed that varied in the level of user involvement for chair adjustments – no involvement without adjustment and high involvement with adjustment, each presented on separate days. Subjective surveys were used at the end of every session to evaluate the chair used in that session that determined individual satisfaction, usability, and perceived discomfort levels. Continuous video obtained during the sessions were analyzed to obtain the number of postural changes (e.g., bending from side to side, shoulders or back ‘drooping’), chair adjustments made, unintended jerks, and chair switches throughout each time period (for a total of 3 time periods) on each day. Performance on the simulated construction science tasks were assessed using a predetermined rubric that included components such as document completion, completed summaries, and presentations to obtain a total performance score. Reported here are preliminary findings from the video analyses and discomfort surveys. A 2-chair x 3-time repeated measures analysis of variance (ANOVA) on postural change over time revealed that postural changes on the chair associated with no involvement without adjustment was higher than that of high involvement with adjustment, however this was only seen in times 1 and 2. This implies that the benefit of adjustments are likely lost over time. Separate one-way ANOVAs were performed on discomfort scores to test the effects of the two chairs. Overall, perceived discomfort across different body regions did not differ between chairs. It is likely that more postural changes were needed to maintain initial comfort levels in the no involvement no adjustment chair studied and were necessary to minimize discomfort. Preliminary findings obtained here will help identify the extent to which postural deviations affect team productivity and responses on discomfort and strain.
This study tested user knowledge and the use of the controls for their work chairs for a volunteer sample of 1004 office workers who were randomly selected for survey from 23 different companies and who were sitting on one of a total of 60 different ergonomic office chairs. Results showed that with the exception of seat height and armrest adjustment, only a small minority of users had accurate knowledge about the controls on their chair. Even when users correctly identified a chair control, less than 50% said they had ever used that control. There was no effect of ergonomics chair training on user perceived chair comfort. Those who had received previous training for an ergonomic chair reported less frequent musculoskeletal discomfort than those with no training or with specific training on their current. Users who sat on chairs with 3 or fewer controls reported significantly less frequent musculoskeletal discomfort than those sitting on more complex chairs with 4 or more controls. Overall, the results show that up to two thirds of users knew about their controls for adjusting seat height, seat depth and armrest height, but most users were unaware of controls for other functions. The implications for chair design are discussed.
We are experiencing today the co-evolution of two distinct approaches to human-centered design research in practice: research that informs the design development process and research that inspires the design development process. Research that informs the design development process has been evolving for many years and is by now well established. Thus, this paper will describe the patterns leading to the emergence of research that inspires the design development process. It will also describe the design spaces (i.e., consuming, experiencing, adapting and co-creating) that are emerging at the intersection of the co-evolution.
We conducted a classification analysis to identify factors associated with sitting comfort and discomfort. The objective was to investigate the possible multidimensional nature of comfort and discomfort. Descriptors of feelings of comfort and discomfort were solicited from office workers and validated in a questionnaire study. From this study, 43 descriptors emerged. The 42 participants rated the similarity of all 903 pairs of descriptors, and we subjected the resulting similarity matrix to multidimensional scaling, factor analysis, and cluster analysis. Two main factors emerged, which were interpreted as comfort and discomfort. Based on these findings, we postulate a hypothetical model for perception of comfort and discomfort. Comfort and discomfort need to be treated as different and complementary entities in ergonomic investigations.
In studies on work it is important to assess various subjective symptoms, complaints, and annoyances. To measure such symptoms, psychophysical ratio scales may be used, as along with simpler category rating scales. In this paper some of the basic concepts and methods of psychophysics have been described. In the field of heavy physical work and the perception of effort and exertion, one of the most popular methods is the rating of perceived exertion. This scale has been presented together with a new category ratio scale, commonly referred to as the CR-10 scale. Some situations in which it is important to obtain measurements of perceived exertion have also been described in the paper.
Driving has been associated with signs and symptoms caused by vibrations. Sitting causes the pelvis to rotate backwards and the lumbar lordosis to reduce. Lumbar support and armrests reduce disc pressure and electromyographically recorded values. However, the ideal driver's seat and an optimal seated spinal model have not been described.
To determine an optimal automobile seat and an ideal spinal model of a driver.
Information was obtained from peer-reviewed scientific journals and texts, automotive engineering reports, and the National Library of Medicine.
Driving predisposes vehicle operators to low-back pain and degeneration. The optimal seat would have an adjustable seat back incline of 100 degrees from horizontal, a changeable depth of seat back to front edge of seat bottom, adjustable height, an adjustable seat bottom incline, firm (dense) foam in the seat bottom cushion, horizontally and vertically adjustable lumbar support, adjustable bilateral arm rests, adjustable head restraint with lordosis pad, seat shock absorbers to dampen frequencies in the 1 to 20 Hz range, and linear front-back travel of the seat enabling drivers of all sizes to reach the pedals. The lumbar support should be pulsating in depth to reduce static load. The seat back should be damped to reduce rebounding of the torso in rear-end impacts. The optimal driver's spinal model would be the average Harrison model in a 10 degrees posterior inclining seat back angle.
Seated work has been shown to constitute a risk factor for low-back pain. This is attributed to the prolonged and monotonous low-level mechanical load imposed by a seated posture. To evaluate the potential health effects with respect to the low back of office chairs with a movable seat and back rest, trunk kinematics, erector spinae EMG, spinal shrinkage and local discomfort were assessed in 10 subjects performing simulated office work. On three separate occasions subjects performed a 3 h task consisting of word processing, computer-aided design and reading. Three chairs were used, one with a fixed seat and back rest and two dynamic chairs, one with a seat and back rest movable in a fixed ratio with respect to each other, and one with a freely movable seat and back rest. Spinal shrinkage measurements showed a larger stature gain when working on the two dynamic chairs as compared with working on the chair with fixed seat and back rest. Trunk kinematics and erector spinae EMG were strongly affected by the task performed but not by the chair type. The results imply that dynamic office chairs offer a potential advantage over fixed chairs, but the effects of the task on the indicators of trunk load investigated were more pronounced than the effects of the chair.
Loading of the spine is still not well understood. The most reliable results seemed to come from the intradiscal pressure measurements from studies by Nachemson, 1966. A new similar study by Wilke et al. (1999) complemented the present study and confirmed some of the earlier data, although it contradicted others. The new data did not confirm that the load on the spine is higher in sitting compared with standing and did not find distinct differences between positions in which subjects were lying down. The objective of this paper was to compare results from two independent in vivo studies (applying different methods) to provide information about spinal loading. In one of these studies (Wilke 1999), intradiscal pressure was measured in one volunteer in different postures and exercises, and in the other study (Rohlmann et al. 1994) the loads on an internal spinal fixation device (an implant for stabilising unstable spines) were determined in 10 patients. The absolute values of the results from both studies were normalized and compared for many body positions and dynamic exercises. The relative differences in intradiscal pressure and flexion bending moments in the fixators corresponded in most cases. Both studies showed slightly lower loads for sitting than for standing and comparatively low loads in all lying positions. High loads were measured for jogging, jumping on a trampoline and skipping. Differences between trends for intradiscal pressure and for flexion bending moments in the fixators were found when the load was predominantly carried by the anterior spinal column, as during flexion of the upper part of the body or when lifting and carrying weights. The combination of the results from these two methods may improve the understanding of the biomechanical behaviour of the lumbar spine and may be used to validate models and theories of spinal loading.
To attract more passengers, new seats were developed for new commuter trains scheduled to run in the United States. Several parties were involved in this study: Long Island Railroad (the commuter train company), Bombardier (the manufacturer of the train), and Multina (the seat manufacturer). TNO was asked to provide design input concerning the overall comfort experienced by passengers. This chapter describes the process that was used to develop a new seat.
A field study was conducted of 40 office workers to determine if seating posture and task differ between job type. Participants were observed through videotape within their own workstations. Torso posture, upper extremity posture and task were coded using event-recording software. Each job type was observed for approximately 31 hours. The job types were categorized as administrative, customer service, executive and technical/professional. Behaviors were examined as frequency of occurrence, duration of occurrence, and percentage of the working hour that the behavior was held. Technical/professional workers spent a significantly greater (p<.05) percentage of the working hour with the mouse in their hand than the other job types. Customer service workers spent a greater (p<.01) percentage of the working hour reading the VDT and typing on their keyboard than the other job types. They also read the VDT more frequently (p<.01) than the other job types. In terms of postures, customer service workers sit with their arms in a neutral posture for a greater (p<.01) percentage of the working hour than the other job types.
To find out how many office workers adjust their chairs, 350 office workers in Spain and the Netherlands are observed and questioned on whether they adjust their chairs. It appears that 24% of 236 Spanish office workers and 61% of 100 Dutch subjects never adjust their chair. If the chair is adjusted, it concerns mostly the seat height. Except for the seat height, other adjustment possibilities are not used by the majority of the study population. Reasons for not adapting could be awareness, complexity of the control system and expected effects.
Recent studies pay considerable attention to body movements, mobility, and stability to measure sitting comfort or discomfort in dynamic conditions. Reviewing the literatures revealed that most of the studies discuss the relations between subjective comfort/discomfort and objective measurements (e.g. body pressure distribution, body movement, and EMG) in short-term sitting, and only several papers reported the studies related to seat comfort during prolonged sitting. The purpose of this study is to investigate the changes in sitting conditions and describe the relationships to sitting dis comfort in prolonged sitting. The pattern change of body pressure distribution, and discomfort experience were studied during VDU tasks. The subjects comprised three males and three females; two different office chairs were used in the study. The different characteristics during 60 minutes sitting were described and compared with each other in time. It appeared that after a while the discomfort increased. When it reached a certain level, macro movement occurred and the pattern repeated. The cycle shortened until the continuous macro movements were observed, and this pattern also repeated. This knowledge could help in understanding the mechanism of discomfort during prolonged sitting.
A technique for measuring the curvature of the lumbar spine is described and evaluated. Two small electronic inclinometers are attached to the skin overlying the spinous processes of L1 and S1. The signal from these inclinometers is stored and then processed to give a record of lumbar curvature against time. Tests showed that recordings from the inclinometers were reproducible and correlated well (r=0.91) with flexion angles measured from X-rays. The dynamic response of the system was good enough to measure lumbar curvature during typical bending and lifting movements.
Comfort is increasingly important in sales of cars, hand tools, seats, earth moving machines and airplane tickets.
Discomfort is a predictor of musculoskeletal injuries and should be reduced in situations that consume a significant part of our time.
However, there is no such thing as a general notion of comfort or discomfort.
Therefore, in research on comfort, the end-user of a product must be involved. If its done on the right way the end-user involvement leads to profitable results, which is shown in several cases in this book.
This book supports managers, designers and researchers in designing products and work stations to increase sales (by comfort increase) and to reduce musculoskeletal injuries (by discomfort reduction). Theory as well as good practices on comfort and discomfort are described for the first time in one book. Examples come from Japan, USA, Sweden, Germany and the Netherlands.
The reader is shown the latest developments in comfort theories on comfort and which factors should be studied to optimise comfort (chapter 1, 2 and 3). The reader gets also the latest knowledge on how to involve participants in comfort research and set up a project (chapter 4). 18 cases (chapter 5 – 22) are described in detail on how discomfort is reduced in a design process or how comfort is improved in this process. Also, on cost/benefits (chapter 23) the reader is informed.
Forward sloping seats are universally accepted based on their increased trunk-thigh angle during sitting. However, these seats are not preferred by some individuals due to reasons such as excessive pressure on knees, difficulties during ingress and egress, and postural fixity during sitting. Some researchers have claimed that forward sloped sitting preserves the lumbar lordosis, thereby making it more comfortable for the sitter. This claim has not been validated across all populations and, therefore, appears to have some disagreement among researchers. In this study, spinal shape during standing and sitting in forward sloping chairs is measured and quantified using a three-dimensional sonic digitizer. Twenty subjects (ten Hong Kong Chinese and ten Indian) have participated in the experiment. Fifteen points on the spine are digitized during standing and sitting in a forward-sloping seat with trunk-thigh angles of 70 degrees, 80 degrees, 90 degrees, 100 degrees, 110 degrees, and 120 degrees. Different measures are used to analyze and differentiate the spinal shape. The correlation between the length of spine during standing and a subject's height is low, but significant. The behavior of the spinal shape change during sitting differs between the populations as shown by the maximum lumbar and maximum thoracic deviations. The Indian subjects seem to approach the standing curvatures in the thoracic region during 30 degrees forward sloping sitting. The Hong Kong Chinese subjects, on the other hand, do not show any resemblance to the standing curvatures during forward sloping sitting. One possible reason could be the differences in arch angle between the two populations. The variations in spinal shape among subjects appear to be similar within a population.
Approximately 33% of visual display terminal (VDT) operators report back and neck pain annually. As a result, a number of “ergonomic” chairs have been developed ranging the price spectrum. The objectives of this study were to (1) assess the effects of monitor height and chair type on low back and neck muscle activity, perceived level of discomfort (PLD), and posture shifts; and (2) determine if chairs at opposing ends of their price spectrum differ in the physiological benefits. Two levels of monitor height and chair type were assessed. The findings of this research indicate that the interaction of monitor height and chair type significantly affects the loads placed on the human body. Task demands also play an important role in the loads placed on the body, posture fixity, and level of discomfort reported. Therefore, the location of VDT equipment and chair selection should be based on task demands to minimize static loading and discomfort. In general, no gross physiological differences were identified between high and low cost chairs, again supporting the recommendation that chair selection be based on task demands.Relevance to industryThis research assesses differences in high and low cost ergonomic chairs as they relate to physiological responses of the back and neck and user perceived discomfort. This information can be used to guide organizations in the purchase of office equipment.
Static working positions and poor postures are both associated with the development of musculo-skeletal disorders and discomfort. An assessment of people's postural behaviour requires suitable measurement tools and scales against which the measure can be judged. Although such methods have been developed, these generally are aimed at assessing gross movements which are undertaken in an industrial setting where the workers are not sedentary. Seated workplaces are more the norm in modern societies and sedentary work does not provide immunity from discomfort and musculo-skeletal disorders. For this reason we have developed a method for classifying and recording seated postural behaviour. This method is described along with the results of studies undertaken using the method at five workplaces. The studies aimed to obtain some base data on sitting behaviour and how it related to work task and chair type. Postures were recorded at one-minute intervals during the subjects' normal work for periods up to two hours. Additionally, questionnaires regarding comfort and musculo-skeletal problems were issued to some of the subjects. Although individual variation was sizeable, the results showed clear postural behaviour differences between the various work tasks. Work tasks which have a higher incidence of musculo-skeletal disorders were found to produce less frequent and less marked postural change. From these results some preliminary conclusions about an optimal seating behaviour pattern are made.
This study investigates whether the same factors underlie comfort in using different kinds of hand tools (screwdrivers, paintbrushes and handsaws). The underlying factors of the hand tools are identified using principal components analysis. The relationships between comfort descriptors (i.e. statements in end-users’ own words that are related to comfort) and comfort factors (i.e. groups of comfort descriptors) with comfort experience are calculated. It is concluded that the same factors (functionality, physical interaction adverse effects on skin and in soft tissues) underlie comfort in different kinds of hand tools, however their relative importance differed. Functionality and physical interaction are the most important factors of comfort in using screwdrivers and paintbrushes (beta 0.73 and 0.67, respectively) and functionality was the most important factor in using handsaws (beta 0.72). Moreover, the most important comfort descriptors differ between different kinds of hand tools. ‘Has a nice feeling handle’ (beta 0.27), ‘fits the hand’ (beta 0.43) and ‘offers a high task performance’ (beta 0.43) are the most important comfort descriptors in using screwdrivers, paintbrushes and handsaws, respectively. Moreover, similarities are seen: ‘Fits the hand’ is associated with comfort in all studied hand tools. The results are applied in a flow chart, which designers can use to address the appropriate comfort descriptors in the hand tool design process.
In the paper a measuring system for the comparative posture and EMG analysis of office chairs is presented. With the system
four specific dynamic office chairs that promote dynamic sitting and therefore aim to prevent musculoskeletal disorders (MSD),
were analyzed in comparison to a reference chair in two different standardized tasks (intensive mouse use and sorting files).
Exemplary results of the ongoing study suggest that postures and the electrical activities of the erector spinae and trapezius
muscles depend more on the tasks performed than on the use of a particular type of office chair. This still has to be proved
by statistical analysis.
Helander and deLooze have proposed a model of seated comfort in which comfort and discomfort are conceptually separate. They argue that ergonomic chairs tend to be overdesigned with insufficient attention paid to aesthetics.
This argument is critiqued on both methodological and conceptual grounds. The methodological critique is based on psychometric
criteria. The conceptual critique is based on the need for an integrated (ecological) approach in which work context and user
characteristics are explicitly considered. An alternative model for an ecological ergonomics is presented.
The risk factors for occurrence of pressure sores--pressure, temperature and humidity--were measured in extensive tests on commercially available wheelchair designs. The effects of different chair positions on the strain and pressure distribution on the backrest, seat surface and foot rests were recorded on a universally adjustable experimental chair. In order to appraise the influence of various types of handicaps, the experiments were conducted with paraplegic, spastic and hemiplegic subjects. It became evident from the results obtained that the currently used suspension belt chairs display serious deficiencies, inherent in their construction principle. Above all, they do not offer an adequately large support area to handicapped persons with severe atrophy of the gluteal muscle. Also, a backrest shape with lumbar pad, as requested by physiologists and orthopaedic surgeons, is technically difficult to realize. Considerable improvements with respect to pressure distribution and orthopaedically correct support of the seated patient can be achieved by using a shell seat construction. In order to enable the handicapped person to use various sitting postures, the backrest should be provided with a rotary joint to the sitting surface.
The anthropometric dimensions of three major ethnic groups in Singapore were studied on 94 female VDU operators. The postural preferences at the VDU work stations were also investigated. Few anthropometric differences were noted for the Chinese, Malays arid Indians. However, when compared to data from Germany and the U.S.A., the three Asian cohorts are smaller in body size. Owing to the smaller body build, the Singapore operators preferred to have a sitting height of about 46 cm, and a working height of about 74 cm, compared with the 47 cm and 77 cm, respectively, preferred by European operators. Despite the anthropometric differences, the Singapore VDU operators, like their counterparts in Europe and the U.S.A. also preferred to sit in a pronounced backward leaning posture with a slightly open elbow angle. This sitting posture seems to ignore the traditional recommended upright trunk position of 90°.
A field study was conducted to assess the preferences of VDT operators with regard to their body posture and the settings of an adjustable VDT workstation. Subjects came from four different companies, and the study took place during subjects' customary working activities. Means and ranges of the preferred settings are given. The operators preferred body postures that are distinctly different from those recommended in textbooks and other publications. Some of the workstation settings they preferred also strongly deviate from such recommendations.
A previous study defined sitting comfort and discomfort as independent entities associated with different factors: discomfort is related to biomechanics and fatigue factors, and comfort to a sense of well-being and aesthetics. In this study a checklist for evaluation of chair comfort and discomfort was analysed in two field studies. In the first study two groups of subjects, ten secretaries and ten managers, evaluated two groups of ten chairs. Subjects assessed each chair three times during a workday using three different types of scales. The results of a factor analysis reconfirmed the factor structure of comfort and discomfort. Analysis of variance demonstrated that discomfort was related to fatigue accumulated during the workday, but it was not related to chair design. There was no significant Chair x Time period interaction, which implies that the rank order of preference among a set of chairs was established during the first assessment and did not change during the day. In a second field study 37 secretaries used three different formats of a Chair Evaluation Checklist with 14 items. The results of a factor analysis again confirmed the factor structure of comfort and discomfort. Analyses of variance demonstrated that subjects can evaluate comfort and discomfort simultaneously without any halo-effect. The results have methodological implications for measurement of comfort and discomfort. The findings for comfort, as defined, carry an important message that aesthetic design matters. This could provide a unifying focus for ergonomists and designers.
This paper presents an inexpensive and simple system to measure the way of use of the backrest. The system can be also used in field studies. It is based on a set of electrodes which, attached to the subject's back and the backrest, allows the contact area to be measured. A laboratory test was performed to validate the system. In the test the spontaneous use of the backrest in standard office chairs and tasks was studied. Four different types of backrest use have been detected, and it has been shown that they determine the lumbar curvature and pelvic inclination angles, as well as postural mobility. The comfort levels observed in the four types of backrest use were also different. Consequently, the system can be used as an indicator of back posture and comfort.
To improve the understanding of factors affecting automobile seat cushion comfort in static conditions (i.e. without vibration), relationships between the static physical characteristics of a seat cushion and seat comfort have been investigated. The static seat comfort of four automobile cushions, with the same foam hardness but different foam compositions, was investigated using Scheffe's method of paired comparisons. The comfort judgements were correlated with sample stiffness, given by the gradient of a force-deflection curve at 490 N (= 50 kgf). Samples with lower stiffness were judged to be more comfortable than samples with greater stiffness. A similar comfort evaluation was conducted using five rectangular foam samples of the same composition but different foam hardness (and a wider range than in the first experiment). There was no linear relationship between the sample stiffness and seat comfort for these samples. Static seat cushion comfort seemed to be affected by two factors, a 'bottoming feeling' and a 'foam hardness feeling'. The bottoming feeling was reflected in the sample stiffness when loaded to 490 N, while the foam hardness feeling was reflected in foam characteristics at relatively low forces. The pressures underneath the buttocks of subjects were compared with the comfort judgements. The total pressure over a 4 cm x 4 cm area beneath the ischial bones was correlated with static seat comfort, even when the differences among samples were great; samples with less total pressure in this area were judged to be more comfortable than samples with greater total pressure. It is concluded that the pressure beneath the ischial bones may reflect both comfort factors: the bottoming feeling and the foam hardness feeling.
The objective of this work is to analyze the causes of lumbar discomfort while sitting on a chair, by analyzing the relationship of lumbar curvature, pelvic inclination and their mobilities with discomfort. An experiment has been performed with healthy subjects, in which comfort, postural and mobility parameters have been measured. Their relationship has been analyzed with multivariate analysis. Factorial analysis has been used to represent all the correlated variables measured. Logistic regression and discriminant analyses have been used to classify discomfort/absence of discomfort. The results show that great changes of posture are a good indicator of discomfort, and that lordotic postures with forward leaned pelvis and low mobility are the principal causes of the increase of discomfort.
Office chairs have often been designed to promote a single 'correct' rather rigid and upright posture, yet it is acknowledged that allowing changes in posture is good ergonomics practice. The present study investigated office worker's preferences for a standard shaped typist's chair (ST) and a prototype multi-posture (PMP) office chair designed to allow its users a variety of sitting positions. Forty-two (22 male and 20 female) telesales personnel (12), clerical staff (12) and researchers (18) used ST or PMP in their workplace for the first week of a 2-week study (with an even number in each work area). The PMP chair was introduced to participants with a brief lecture on how to use it and with an information booklet. Following this, each participant completed a chair comfort questionnaire. In the second week, participants swapped chairs and again completed the chair comfort questionnaire. At the end of the second week participants were also asked to complete a separate questionnaire about the usability of the information booklet that accompanied the PMP chair. Statistically significant differences in subject's rating of the two chairs were observed in 7 out of 19 questions. On a 100 mm scale, the ST chair was rated as having a greater mean overall acceptability, desirability and suitability for body build than the PMP chair. Participants also claimed to achieve better posture in the ST chair, that they tipped forward less and were more satisfied with its width. Although the participants generally preferred the ST chair, the PMP chair received more favourable ratings among the researchers who were quite mobile in their work, and in whom there was a trend for less neck, shoulder and upper back discomfort. More participants reported an overall preference for the PMP chair. The findings suggest that a more aesthetically acceptable PMP chair should be developed, peoples' reasons for preferring a more traditionally designed chair should be explored, and that the effect of postural stability education on personal preconceptions should be examined to obtain an optimal combination of healthy sitting habits, comfort and aesthetic qualities in an office chair.
Automobile seat design specifications cannot be established without considering the comfort expectations of the target population. This contention is supported by published literature, which suggests that ergonomics criteria, particularly those related to physiology, do not satisfy consumer comfort. The objective of this paper is to challenge ergonomics criteria related to anthropometry in the same way. In this context, 12 subjects, representing a broad range of body sizes, evaluated five different compact car seats during a short-term seating session. Portions of a reliable and valid survey were used for this purpose. The contour and geometry characteristics of the five seats were quantified and compared to the survey information. Discrepancies were discovered between published anthropometric accommodation criteria and subject-preferred lumbar height, seatback width, cushion length, and cushion width. Based on this finding, it was concluded that automobile seat comfort is a unique science. Ergonomics criteria, while serving as the basis for this science, cannot be applied blindly for they do not ensure comfortable automobile seats.
The concepts of comfort and discomfort in sitting are under debate. There is no widely accepted definition, although it is beyond dispute that comfort and discomfort are feelings or emotions that are subjective in nature. Yet, beside several subjective methodologies, several objective methods (e.g. posture analysis, pressure measurements, electromyography (EMG) are in use to assess sitting comfort or discomfort. In the current paper a theoretical framework is presented, in which comfort and discomfort were defined and the hypothetical associations with underlying factors were indicated. Next, the literature was reviewed to determine the relationships between objective measures and subjective ratings of comfort and discomfort. Twenty-one studies were found in which simultaneous measures of an objective parameter and a subjective rating of comfort or discomfort were obtained. Pressure distribution appears to be the objective measure with the most clear association with the subjective ratings. For other variables, regarding spinal profile or muscle activity for instance, the reported associations are less clear and usually not statistically significant.
A programme was designed in which instruction was given in the optimal adjustment of seat and desk height based on individually measured body dimensions. The programme was evaluated by means of measurement of seat and desk height before and after instruction to an experimental group in comparison with a control group to which no instruction was given. In the experimental group, prior to instruction, the mean deviation from the ideal sitting posture measured 71 mm for seat height and 70 mm for desk height. After instruction this deviation decreased by 11 mm for seat height and 18 mm for desk height. Although this is a statistically significant change, it is of limited practical importance since for seat height only 7% (3 of 41) and for desk height 13% (5 of 40) adjusted their furniture effectively as they were advised. The reasons for this meagre result are assumed to be the arbitrary concept of an ideal sitting posture, difficulties in obtaining extra adjustments in the form of footrests and desk elevation, the social acceptability of the advice given, and practical impediments that can occur while adopting an ideal sitting posture.
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