Postural Comfort Research Articles

The Automotive Vibrations Effect on the Comfort Degree Determined at the Level of Foot-Shoe Composite Structure

A number of issues related to the effect of vibration analysis, developed inside a car, the comfort level led to the composite structure of the whole foot and shoes is presented in this paper. Variants of composite structures consisting of biomechanical system - the human body, foot and shoe variants that undergo analysis are presented in the first part of the paper. Also human body models are presented and analyzed in connection with the surface and place inside the car driving. This study aims to determine the physiological limits of stability of the locomotor system, barefoot and wearing shoes, with or without insoles, over a period of time the car is driven. The experimental system and methodology for analysis are described in the second part of the paper. The third part of the paper presents the results and conclusions obtained from this study and determining the postural comfort degree (PCD).

Proposal of a new quantitative method for postural comfort evaluation

In Human–Machine Interface (HMI) design, several parameters have to be correctly evaluated in order to guarantee a good level of safety and well-being of users (humans) and to avoid health problems like muscular-skeletal disease. ISO Standards give us a good reference on Ergonomics and Comfort: ISO 11228 regulation; it deals with qualitative/quantitative parameters for evaluating Postural Ergonomics, using a “Postural Load Index”, in push/pull, in manual loads' lifting and carrying and in repetitive actions; those parameters can represent the Ergonomics level of examined posture. While bibliographic references suggest different methods to make ergonomic evaluation like RULA, LUBA and REBA, the state of the art about comfort/discomfort evaluation shows the need of an objective method to evaluate “effect in the internal body” and “perceived effects” in several schemes of comfort perception like Moes', Vink & Hallback's and Naddeo & Cappetti's ones; postural comfort is one of the aspect of comfort/discomfort perception and this paper proposes a new quantitative method for evaluating this aspect of comfort, based on anthropometric parameters and upper limbs posture. The target of this paper is to present and test a “general purpose” method of comfort-measurement that can be applied to different industrial cases: in workspace environments, in automotive passenger compartments, in aeronautic cockpit or in industrial assembly lines. Relevance to industryThe method presented in this paper may allow industrial designers to provide an assessment of products' perceived comfort in the early stage of the product development process by making a posture-based quantitative evaluation; it also allows designers to make a comfort driven redesign of existing products' configuration for improving and innovating them.

Ergonomic assessment of primary school furniture in United Arab Emirates

Background: In many developing countries, anthropometric measures are rarely available and dimensions of school furniture are either based on anthropometric measures from developed countries or are arbitrarily determined. Objective: The purpose of this study was to ergonomically assess classroom furniture dimensions in United Arab Emirates as compared to students' anthropometric measures. Methods: Relevant anthropometric dimensions of a sample of 200 grade 6 students were measured in two large schools in Dubai and Sharjah. Dimensions of furniture used by these students were also measured and compared to their anthropometric measures. Results: Results show that there was a major mismatch between many anthropometric measures and classroom furniture dimensions. Conclusions: There is a great discrepancy between furniture dimensions and anthropometrics measures of students. To ensure postural comfort. a new set of furniture dimensions for grade 6 classrooms in is suggested based on anthropometric dimensions of students.

Manual Assembly Workstation Redesign Based on a New Quantitative Method for Postural Comfort Evaluation

Main purpose of this work is to show how easy and economics an ergonomic/comfort based approach, in re-design a manual assembly workplace, can be; authors, using a new comfort/ergonomic evaluation criterion, analyzed a workstation and identified the critical issues under ergonomic/comfort point of view and finally gave several guidelines to re-design the workplace, implementing minor modification, and improve work-safety, work-quality and productivity. The postural analysis was performed by non-invasive and especially inexpensive methods, based on cameras and video-recorder use and by photogrammetric analysis; DELMIA® DHM software has been used to perform all simulations; comfort analysis was performed by the software developed by researchers of Departments of Industrial Engineering of Salerno: CaMAN®. The test case is an automatic assembly machine that has been modeled and used for virtual postural analysis. Main results of this work can be found in a very good numerical/experimental correlation between acquired/simulated postures and real ones, and on the powerful use of an objective comfort evaluation method, based on biomechanics and posture analysis, for giving to designers the guidelines to re-design a workplace and a work-cycle. This kind of approach seemed to be very powerful in re-designing the work-place and in re-scheduling the work time-sheet because it allowed to improve an ergonomic corrective action with minor costs for company. Obtained results demonstrated the validity of re-design hypotheses through the increase of all comfort indexes and the improvement of workstation/operator productivity.

Postural comfort evaluation: experimental identification of Range of Rest Posture for human articular joints

In this paper we introduce and describe a new concept in human-measurements operation that seems to be very useful for comfort evaluation: the Range of Rest Posture (RRP). Our study is focused on the identification of RRP -inside the comfort range of motion (CROM)—for the following human joints: neck, shoulder, elbow, wrist and ankle. Method used is based on a wide experimental work on 85 healthy individuals (43 males and 42 females) ranging in age from 20 to 30 year. The main target of this work is the experimental definition of CROM and identification of RRP; Experimental data has been processed by statistical methods for identifying the best statistical distribution in order to fit experimental data. Main result is the identification of RRP in CROM of main human joints involved in upper and lower limbs movements. In RRP weve found several maximum level of comfort positions in human postures: those position seems to be one of the most important information in comfort evaluation analysis. The state of the art about comfort/discomfort evaluation shows the need of an objective method to evaluate effect in the internal body and perceived effects in Moes (Contemporary ergonomics. Taylor & Francis, London, 2005) and Vink and Hallback (Appl Ergon 43:271–276, 2012) scheme of comfort perception; postural comfort is one of the aspect of comfort/discomfort perception and this paper helps to put a piece in the puzzle of posture evaluation. On the basis of papers results, a comfort evaluation method can be developed using RRP, CROM and building a composition rule that takes into account also lumbar comfort and H-point. Our work does not use ROM and CROM values coming from literature because each of these values has been experimentally identified.

Ergonomic Design of a Main Control Room of Radioactive Waste Facility Using Digital Human Simulation

The present study evaluated a preliminary main control room (MCR) design of radioactive waste facility using the JACK® digital human simulation system. Four digital humanoids (5th, 50th, 95th, and 99th percentiles) were used in the ergonomic evaluation. The first three were selected to represent 90% of the target population (Korean males aged 20 to 50 years) and the last to reflect the secular trend of stature for next 20 years in South Korea. The preliminary MCR design was assessed by checking its compliance to ergonomic guidelines specified in NUREG-0700 and conducting an in-depth ergonomic analysis with a digital prototype of the MCR design and the digital humanoids in terms of postural comfort, reachability, visibility, and clearance. For identified design problems, proper design changes and their validities were examined using the JACK. A revised MCR design suggested in the present study would contribute to effective and safe operations of the MCR as well as operators’ health in the workplace.

Different influences on patients hemodynamics between the prone position and supine position percutaneous lithotripsy

Objective To compare the clinical characters and hemodynamic data of the prone position and supine position percutaneous nephrolithotomy. Methods Patients with kidney stones in 100 cases were randomly assigned into the supine position group and prone position group.There were 50 cases in each group.The following data were recorded at preoperative,intraoperative,change position:the blood pressure,heart rate,respiration,saturation of blood oxygen and blood gas analysis results.The VAS score was recorded in patients for postural comfort,dyspnea and pain score. Results The systolic blood pressure in the preoperative,intraoperative,postoperative on supine position and prone position were as follows:(137±12),(119±15),(115±17) mm Hg and (137±10),(110±18),(104±16) mmHg.The diastalic blood pressure was as follows:( 81 ± 9 ),(74 ± 8 ),(63 ± 14 ) mm Hg and ( 84 ± 8 ),(63 ± 9 ),(60 ± 15) mm Hg.Compared with preoperative,there was a blood pressure decreased in both groups.The blood pH at preoperative,intraoperative,postoperative in supine position and prone position:7.4 ± 0,7.3 ± 0,7.3 ± 0 and 7.4 ± 0,7.3 ± 0,7.3 ± 0.The bass excess (BE) of two groups were:(2.1 ± 0.5),(-2.7 ±0.5),( -1.5 ±0.5) mmol/L and (3.2 ±0.5),(-3.8 ±0.5),(-2.5 ±0.5) mmol/L.Compared with preoperative data,the pH and BE declined in both groups.The prone position had more pronounced decrease in serum sodium,serum potassium; but with no significant difference.Supine group in postural comfort and breathing difficulties were 1.6 ± 0.4 and 7.1 4± 05,while prone group were 7.5 ± 0.2 and 1.4 ± 0.3.The supine position showed better in postural comfort and breathing difficulties with statistical significance. Conclusions Compared with the prone position,the supine positioned percutaneous nephrolithotomy could have less influence on hemodynamics,blood gas analysis.It could have better postural comfort. Key words: Nephrostomy; percutaneous; Posture; Hemodynamics; Blood gas analysis

Digital Human Simulation을 활용한 방사성 폐기물 처리장 주제어실의 인체공학적 평가

The present study evaluated a preliminary control room (CR) design of radioactive waste facility using the human simulation system. Four digital humanoids (, , , and percentiles) were used in the ergonomic evaluation. The first three were selected to represent 90% of the target population (Korean males aged 20 to 50 years) and the last to reflect the secular trend of stature for next 20 years in South Korea. The preliminary CR design was assessed by checking its compliance to ergonomic guidelines specified in NUREG-0700 and conducting an in-depth ergonomic analysis with a digital prototype of the CR design and the digital humanoids in terms of postural comfort, reachability, visibility, and clearance. For identified design problems, proper design changes and their validities were examined using JACK. A revised CR design suggested in the present study would contribute to effective and safe operations of the CR as well as operators' health in the workplace.

Enhancing digital driver models: Identification of distinct postural strategies used by drivers

Driver workspace design and evaluation is, in part, based on assumed driving postures of users and determines several ergonomic aspects of a vehicle, such as reach, visibility and postural comfort. Accurately predicting and specifying standard driving postures, hence, are necessary to improve the ergonomic quality of the driver workspace. In this study, a statistical clustering approach was employed to reduce driving posture simulation/prediction errors, assuming that drivers use several distinct postural strategies when interacting with automobiles. 2-D driving postures, described by 16 joint angles, were obtained from 38 participants with diverse demographics (age, gender) and anthropometrics (stature, body mass) and in two vehicle classes (sedans and SUVs). Based on the proximity of joint angle sets, cluster analysis yielded three predominant postural strategies in each vehicle class (i.e. ‘lower limb flexed’, ‘upper limb flexed’ and ‘extended’). Mean angular differences between clusters ranged from 3.8 to 52.4° for the majority of joints, supporting the practical relevance of the distinct clusters. The existence of such postural strategies should be considered when utilising digital human models (DHMs) to enhance and evaluate driver workspace design ergonomically and proactively. Statement of Relevance: This study identified drivers' distinct postural strategies, based on actual drivers' behaviours. Such strategies can facilitate accurate positioning of DHMs and hence help design ergonomic driver workspaces.

Postural Comfort Inside a Car: Development of an Innovative Model to Evaluate the Discomfort Level

How can car designers evaluate device’s position inside a car today? Today only subjective tests or “reachability” tests are made to assess if a generic user is able to reach devices, but it’s no longer enough. The aim of this study is to identify an instrument (index) that is able to provide a numerical information about the discomfort level connected with a posture that is kept inside a car to reach a device, by this instrument it should be possible not only judge a posture, but also compare different solutions and get rapid and accurate evaluations. In the state of the art there are many indexes developed to evaluate postural comfort (like RULA, REBA and LUBA [3, 4, 5]) but none of them has been realized to evaluate postures’ conditions that can be detected inside a car, so their evaluations cannot be acceptable. There are also many other studies (like Porter and Gyi, Krist, Grandjean, Rebiffe, Dreyfuss 2D and 3D) which deal with postural comfort inside car, but they have only assess neutral angles and ranges of comfort, so their evaluations are qualitative and discontinuous. For these reasons it has been realized a new instrument (implemented by our research group using MatlabTM) to give the wanted numerical evaluation; it is based on an human scale manikin that can reproduce each user and each posture which can be introduced directly or imported from a digital human modeling (DHM) software (like JACKTM developed by U.G.S.), on discomfort functions (one for each degree of freedom of the manikin) and on a method (based on the distribution of the weights of the human body on the different joints) to aggregate them and return total discomfort values.

Effects of two hospital bed design features on physical demands and usability during brake engagement and patient transportation: A repeated measures experimental study

Background Work-related musculoskeletal disorders (WMSDs) are prevalent among healthcare workers worldwide. While existing research has focused on patient-handling techniques during activities which require direct patient contact (e.g., patient transfer), nursing tasks also involve other patient-handling activities, such as engaging bed brakes and transporting patients in beds, which could render healthcare workers at risk of developing WMSDs. Objectives Effectiveness of hospital bed design features (brake pedal location and steering-assistance) was evaluated in terms of physical demands and usability during brake engagement and patient transportation tasks. Design Two laboratory-based studies were conducted. In simulated brake engagement tasks, three brake pedal locations (head-end vs. foot-end vs. side of a bed) and two hands conditions (hands-free vs. hands-occupied) were manipulated. Additionally, both in-room and corridor patient transportation tasks were simulated, in which activation of steering-assistance features (5th wheel and/or front wheel caster lock) and two patient masses were manipulated. Participants Nine novice participants were recruited from the local student population and community for each study. Methods During brake engagement, trunk flexion angle, task completion time, and questionnaires were used to quantify postural comfort and usability. For patient transportation, dependent measures were hand forces and questionnaire responses. Results Brake pedal locations and steering-assistance features in hospital beds had significant effects on physical demands and usability during brake engagement and patient transportation tasks. Specifically, a brake pedal at the head-end of a bed increased trunk flexion by 74–224% and completion time by 53–74%, compared to other pedal locations. Participants reported greater overall perceived difficulty and less postural comfort with the brake pedal at the head-end. During in-room transportation, participants generally reported “Neither Low nor High” physical demands with the 5th wheel activated, compared to “Moderately High” physical demands when the 5th wheel was deactivated. Corridor transportation was similarly reported to be easier when a steering-assistance feature (the 5th wheel or front caster lock) was activated. Conclusions Braking and steering-assistance features of hospital beds can have important effects on task efficiency and physical demands placed on healthcare workers. Selection of specific designs may thus be able to improve productivity and contribute to a reduction in WMSDs risk among healthcare workers.

Workspace zone differentiation tool for visualization of seated postural comfort

Over the past several years, significant advances have been made in the area of posture prediction. However, to make simulations more useful for vehicle design, additional unique tools are needed. This research focuses on the development of one such tool, called workspace zone differentiation or zone differentiation. This new tool allows users to visualize not only the complete reach envelope but also the interior comfort levels of the envelope. It uses a color map to display the relative values of various human performance measures (i.e., comfort) at points surrounding an avatar. This is done by leveraging an optimization-based approach to seated posture prediction. Using this tool, a vehicle designer can visually display the impact that the placement of a control (switch, button, etc.) has on a driver's seated postural comfort. The comfort values are displayed in a manner similar to how finite element analysis (FEA) programs display stress and strain results. Within multi-objective optimization (MOO) for seated posture prediction, the objective function is defined as the mathematical rating model for discomfort. A direct mapping method is used to correlate subjective (survey) comfort levels with the mathematical rating model. Based on the correlated mathematical model, we develop the graphical user interface to display the comfort zones.

Leg strength of Indian operators in the operation of tractor pedals

Tractors require more pedal force than road vehicles. The ergonomics literature concerning human strength in the operation of control pedals although extensive is not adequate for a tractor designer. The study was aimed to quantify human strength in the operation of tractor control pedals by Indian operators. The leg strength data of 20 male tractor operators were measured using a strength measurement set-up. The leg (right and left legs) strength data were collected at five horizontal (35%, 40%, 45%, 50% and 55% stature) and six vertical (10%, 13%, 16%, 19%, 22% and 25% stature) locations of foot pedal from the seat reference point (SRP) keeping the lateral distance from mid line constant. The analysis of data indicated that the force exerted by right leg was higher as compared to that exerted by left leg. It was also observed that the fifth percentile male tractor operator could reach 810 mm in front and 370 mm below the SRP. The maximum leg strength values of 655 and 613 N for right and left legs, respectively was observed when the pedal was located at 55% stature in front and 10% stature below the SRP i.e. when the leg was in almost elongated position. It was also observed that the actuating force limits as given in IS: 10703 [1992. Agricultural tractors—maximum actuating forces required to operate controls. IS 10703-1992]/ISO TR 3778 [1987. Agricultural tractors—maximum actuating forces required to operate controls. ISO/TR 3778] are very high as compared to leg strength data of Indian operators. It may be concluded that the optimum location of clutch and brake pedals on Indian tractors should be at 40% stature in front and 19% stature below the SRP based on strength limits and postural comfort of operators. It may be recommended that the limits for maximum actuating force for brake and clutch pedals should be 330 and 280 N, respectively. Relevance to industry The study emphasizes the need to optimally locate and design tractor control pedals based on strength limits of operators by the tractor manufacturing industry. This will not only enhance the comfort and safety of the tractor operators but also increase work output from the tractor on per day basis. The findings of the study will also be helpful for tractor operators in other Asian countries.

다변량 통계기법을 활용한 표준 운전자세의 도출

The package layout of a vehicle is very important to the driver's postural comfort. It considers human body characteristics of drivers and passengers, and uses the anthropometric data on driver's posture. Especially, since the human bodies were scanned in Size Korea project, three-dimensional human shape data have been considered the useful data in vehicle design stage. The proper driver's postural data are necessary in order to apply three-dimensional human data or ergonomic human models to package layout. Traditional postural data were provided to each joint angle individually, such as elbow angle, shoulder angle, hip angle, and knee angle. However, it is not appropriate to account for the human posture because the limbs move in coupled with each other. In the study, some whole-body posture were derived by multivariate statistical analysis to develop driver's standard posture, which may be used for reference data in application of human model software or human shape data in CAD environment. From the clustering analysis five whole-body postures were classified for the driver's representative posture. This study demonstrates that the combination of the most frequent angles of each joint can not explain the driver's actual posture in car, and that the joint angles must be considered together as a whole-body posture. It is expected that this study is helpful for the package layout designer to understand the driver's posture and to apply the human shape data to vehicle design.

Comfort analysis of car occupants: comparison between multibody and finite element models

This paper deals with numerical models developed in order to simulate the vibrational and postural comfort of car occupants. The proposed models have been based on different mathematical approaches: the first is a multibody dynamics model and the second is a finite elements model. Both models have been validated by means of static and dynamic experimental tests on vehicles using appropriate test rigs. The authors focus on the advantages and disadvantages of each model in order to have useful information about which approach has to be used to predict objectively the comfort of driver and passengers.

Constraints on grip selection in hemiparetic cerebral palsy: effects of lesional side, end-point accuracy, and context

This study was concerned with selection criteria used for grip planning in adolescents with left or right hemiparetic cerebral palsy. In the first experiment, we asked participants to pick up a pencil and place the tip in a pre-defined target region. We varied the size of the target to test the hypothesis that increased end-point precision demands would favour the use of a grip that affords end-state comfort. In the second experiment, we studied grip planning in three task contexts that were chosen to let us test the hypothesis that a more functional task context would likewise promote the end-state comfort effect. When movements were performed with the impaired hand, we found that participants with right hemiparesis (i.e., left brain damage) aimed for postural comfort at the start rather than at the end of the object-manipulation phase in both experiments. By contrast, participants with left hemiparesis (i.e., right brain damage) did not favour a particular selection criterion with the impaired hand in the first experiment, but aimed for postural comfort at the start in the second experiment. When movements were performed with the unimpaired hand, grip selection criteria again differed for right and left hemiparetic participants. Participants with right hemiparesis did not favour a particular selection criterion with the unimpaired hand in the first experiment and only showed the end-state comfort effect in the most functional tasks of the second experiment. By contrast, participants with left hemiparesis showed the end-state comfort effect in all conditions of both experiments. These data suggest that the left hemisphere plays a special role in action planning, as has been recognized before, and that one of the deficits accompanying left brain damage is a deficit in forward movement planning, which has not been recognized before. Our findings have both theoretical and clinical implications.

The Postural Comfort Zone for Reaching Gestures

We have proposed a method for objective assessment of postural comfort (Kölsch et al., 2003). We defined comfort as the range of postures that is voluntarily assumed despite the availability of other postures. Designing user interfaces within the limits of comfort zones can avert risks associated with unknown alternative use patters of the interface. Here we report on a user study that investigated the comfort zone for free-hand gestures in the horizontal plane at about stomach height. This space is of particular interest to novel technologies such as gesture recognition and virtual reality. The results are in line with previous studies on postural discomfort, but improve on resolution and are not based on subjective, questionnaire-based data acquisition. This study also serves as an example for how to design studies for comfort evaluation.

The Ibis sustainable wheelchair: moving people with the times

This article reviews the Ibis; a compact adaptable manual wheelchair that offers postural support, comfort and ease of use both indoors and out. The Ibis has a sustainable wheelchair design that may be refurbished and reused to reduce the tension on health-care purse strings, and a wide variety of features that are easy to manipulate.

The boundaries for joint angles of isocomfort for sitting and standing males based on perceived comfort of static joint postures

This study presents data for the joint angles of isocomfort (JAI) in sitting and standing males based on perceived comfort ratings for static joint postures maintained for 60 s. The JAI value was defined as a boundary indicating joint deviation (an angle) from neutral posture, within which the perceived comfort for different body joint postures is expected to be the same. An experiment for quantifying perceived comfort ratings was conducted using the free modulus method of magnitude estimation. Based on experimental results, regression equations were derived for each joint posture, to represent the relationships between different levels of joint deviation/joint posture and corresponding normalized comfort scores. The JAI values were developed for nine verbal categories of joint comfort. The JAIs with the marginal comfort levels, one of the nine verbal categories used, for most joint postures around the wrist, elbow, neck and ankle were similar to the maximum range of motion (ROM) values for these joints. However, the JAIs with the marginal comfort category for back and hip postures were much smaller than the maximum ROM values for these joints. There were no significant differences in JAI expressed in terms of the percentage of the corresponding maximum ROM values between sitting and standing postures. The relative ‘marginal comfort index’, defined as the percentage of JAIs for the marginal comfort relative to the corresponding maximum ROM values, for the hip was the smallest among all joints. This was followed, in an increasing order of the marginal comfort index, by the lower back and shoulder, while the marginal comfort index for the elbow joint was the largest. The results of this study suggest that static postures maintained for 60 s cause greater discomfort for the hip joint than for the other joints studied, and less discomfort for the elbow than for the other joints. The data about JAIs can be used as guidelines for enhancing postural comfort when designing a variety of human-machine tasks where static postures cannot be eliminated.

Computer Ergonomics for Teachers and Students

To define the need for computer ergonomics among elementary public schools (Kindergarten – 6th grade) a survey was conducted in 228 schools in Oregon, USA. Two hundred eighteen teachers, 32%, responded. The survey addressed issues related to: students' computer workstation set up and work habits; teachers' perception of students postural and visual comfort level during computer use in school; teacher education in ergonomics and computer skills; teachers' views on a computer ergonomics education program and ways to introduce it into school activities. A pilot program presented as a free ergonomic resource web site was developed based on the survey results.