Chair Seat Research Articles

A METHOD OF SIMULATING SEAT LOAD FOR NUMERICAL ANALYSIS OF WOOD CHAIR STRUCTURE

This study aimed to investigate the characteristic values of the human-seat interface in a normal sitting posture, and to numerically mode the load on the chair seat for the structural design of chairs. The stress distributions and the characteristic values of seat were measured under normal sitting posture by using a human body pressure distribution measurement system considering the effects of gender and body mass index (BMI). The stress distribution on the seat was then numerically modeled using three modeling methods. The observed results and the numerical analysisresults were compared. The results showed that an inverted U-shaped pressure distribution was observed in normal sitting posture. The stress was concentrated on the ischial tuberosity with a maximum value of 0.066 MPa. The ratio of the load on the seat to the gravity of the human body weight was about 65.3%. The numerical model established using the body pressure mapping method was superior to those of the uniform load method and the standard loading pad method in terms of stress distribution, maximum stress, and contact area.

A trace fiber population study on upholstered chairs in a military environment

This fiber population study has assessed the prevalence of the color and type of trace fibers present on upholstered seats in a specific setting to identify the most common and rare colors and to determine their evidentiary value. Nearly 22,000 fibers were collected via tape lifts from 25 fabric covered chair seats in a lobby area on Beale Air Force Base and examined microscopically to determine their apparent colors. Overall, blue and white/colorless were the most and nearly equally common colors (32.0 % and 31.5 %, respectively), followed by black/grey (19.6 %), brown (8.6 %), yellow/tan (4.9 %), and red/pink (2.5 %), while orange, purple, and green were the rarest (0.5 %, 0.3 %, and 0.3 %, respectively). Among rarest color fibers, plant-based fibers were predominant (77.7 %), consisting of mainly cotton, followed by synthetic fibers (17.4 %), then the least prevalent animal fibers (5.0 %). These color rankings align similarly to previous studies, despite the prominence of blue color fibers and higher proportions of brown and yellow/tan color fibers.

Kinematic Factors of Sitting Posture for Musculoskeletal Pain in University Staff

Aims: The objective of the present study was to verify the relationship between musculoskeletal pain and kinematic factors of sitting posture in university staff at the University of Middle-West –UNICENTRO. Methodology: The sample studied was 24 university agents from a total of 40 employees. Anthropometric data were collected by record and to assess the prevalence of pain, a standardized questionnaire was used. The employee positioning variables were: popliteal height, elbow-to-seat height, table height and thigh height. The arrangement of the workstation was also evaluated, checking the position of the computer and/or other equipment for daily use. Results: It was found that 54.16% of the agents had some type of pain in the spine. The recommended chair seat for men would be a height of 44.3 cm and was found to be 50.2 cm, while for women the recommended height is 40.9 cm and was found to be 45.1 cm. Conclusion: According to the results obtained, the height of the table was higher than recommended, which could perhaps justify the complaint of pain reported by university agents.

The Art of the Review

What’s a book review for? You might think it’s to supply a summary of the book. Time is short. We’re drowning in stuff to read; it’s hard to keep up even if you dutifully apply the seat of your pants to the seat of your chair and read very fast. Courts are constantly publishing new opinions. And—even though you’re used to this familiar feature of American law, you should still notice how startling it is—they’re also publishing unpublished opinions, with indefensible rules about whether or how they count as precedents lawyers can cite. Legislatures are publishing floor debates, not to mention committee hearings, and passing new statutes, the latter apparently written by Bulgarian bureaucrats struggling in their fifth semester of English as a second language. Don’t get me started on what the agencies are up to. (Quick! how many pages were added to the Federal Register while you read this paragraph?) Especially if you fear that some books should have been articles and that most law review articles are too long, you can be forgiven for basking in deep and abiding gratitude to the reviewer who boils things down. If you’re the tiniest bit unscrupulous, you can then pretend to have read the book yourself. You can even cite it, though I hope you have enough of a scholarly conscience left to feel uneasy about that morsel of cheating. (I hope too that “scholarly conscience” is not an oxymoron.) And you can be baffled or annoyed—I am—by the kinds of “reviews” that sometimes appear in, oh, The New York Review of Books and the Times Literary Supplement, where the ostensible reviewer can barely be bothered to mention the book she’s allegedly reviewing, but just wants to tell you what she would have said had she written a book on the topic.

A quantitative study on the impact of educational modules on the awareness of postural ergonomics among the dental clinical trainees of Jouf University: A North Saudi Arabian Cohort

This research aimed to evaluate the difference between self-reported and actual work postures among dental clinical trainees and the effect of health education on their ergonomic postures. Bad postures induce fatigue, musculoskeletal pain, errors, a negative attitude, and job dissatisfaction. It is necessary to evaluate the awareness of posture ergonomics among clinical trainees as the bad postures captured during their learning years transform into habits that could affect future productivity. Hence, a three-level quantitative study was conducted among the dental trainees at Jouf University, Saudi Arabia. The first level comprised a self-reported survey and an observational study to record the working postures of the participants. At the second level, appropriate health education is customized based on the findings observed at the first level. An unannounced observational study was conducted at the third level to assess the impact of ergonomic education on the working postures of the participants. Gender and the academic year level of the participants were the variables considered in the study. The study found that the participants overrated their correct postures (P = 0.005). Fortunately, the final post-ergonomic education observations found a significant improvement in work posture (8.6 vs 12.4), regardless of the variables considered in the study (P = 0.001). The three best correct postures were placing the feet resting on the floor (52.6 vs 92.8 %), using the seat of a dental chair (57.9 vs 89.5 %), and using an upright position of the legs at the thigh-to-leg angle (53.9 % vs 86.2 %). Therefore, the study emphasizes the importance of training in ergonomics and regular, periodic observation to eradicate bad postures before they become a habit among young dentists.

Knitted Heating Mats

Abstract The paper deals with conceptual designs and research on flexible knitted heating mats differing in construction from textile heaters on low-elastic woven or nonwoven-foil substrates. Two variants of heating mats with elasticity from 100 to 300 % of relative elongation were designed and manufactured using knitting technology. The heating elements of the mats were parallel-connected sets of electrically conducted carbon threads and synthetic threads coated with silver. With considerable elongation in the range of 210÷270 % no damage was observed to the heating elements and resistance changes during the stretching process equaled from 0.015 to 0.22 Ω/% of elongation. The optimum power of the knitted heater in the range from 16 to 41 W, with high thermal efficiency for a 12 V supply voltage, was obtained thanks to proper density of the electrically conductive threads (resistors) and the appropriate structure of the knitted fabric. The surface temperature of the heater can be adjusted from 34 to 43 °C, which corresponds to human thermal comfort. One of the variants of the knitted heaters was applied in the construction of the seat and backrest of an office chair.

Prevalence of Musculoskeletal Pain and Its Association with Computer Workstation Ergonomics among Undergraduates in Malaysia

Background: Advanced technology promotes students to utilize computers widely for educational purposes, leading to increased musculoskeletal (MSK) pain among undergraduates. This study aimed to identify the prevalence of various MSK pain and its association with computer workstation ergonomics among undergraduates in Malaysia. Method: A cross-sectional study was conducted using a self-administered online questionnaire among 390 undergraduates. Data on Nordic Musculoskeletal Questionnaire and Computer Workstation Checklist were collected. Descriptive statistics were used to evaluate the prevalence of MSK pain and its association with computer workstation ergonomics was analysed using the chi-square test. Results: 79.1% and 52.7% of the participants reported MSK pain in the past 12 months and 7 days respectively. This study also revealed that pain in the neck, elbow, wrist, lower back, hip, knee, and ankle in the past 12 months were associated with the computer workstation ergonomics, namely the height of the armrest, keyboard, and input device, monitor’s viewing distance and level, the usage of a comfortable keyboard, comfortable input device and document holder, with p<0.05. Whilst pain in the neck, wrist, and knee in the past 7 days were associated with the chair seat width, monitor’s distance and height, obstruction under the table, and usage of document holder, with p<0.05. Conclusion: This study revealed that more than half of the undergraduates have experienced MSK pain and there is an association with computer workstation ergonomics. Therefore, undergraduates should be educated on the proper computer workstation ergonomics as a preventive measure for MSK pain.

IoT System for Real-Time Posture Asymmetry Detection

The rise of the Internet of Things (IoT) has enabled the development of measurement systems dedicated to preventing health issues and monitoring conditions in smart homes and workplaces. IoT systems can support monitoring people doing computer-based work and avoid the insurgence of common musculoskeletal disorders related to the persistence of incorrect sitting postures during work hours. This work proposes a low-cost IoT measurement system for monitoring the sitting posture symmetry and generating a visual alert to warn the worker when an asymmetric position is detected. The system employs four force sensing resistors (FSR) embedded in a cushion and a microcontroller-based read-out circuit for monitoring the pressure exerted on the chair seat. Java-based software performs the real-time monitoring of the sensors’ measurements and implements an uncertainty-driven asymmetry detection algorithm. The shifts from a symmetric to an asymmetric posture and vice versa generate and close a pop-up warning message, respectively. In this way, the user is promptly notified when an asymmetric posture is detected and invited to adjust the sitting position. Every position shift is recorded in a web database for further analysis of the sitting behavior.

Comfort Prediction of Office Chair Surface Material Based on the ISSA-LSSVM

This study serves the purpose of assisting users in selecting a comfortable seat surface material for office chairs and enhancing users' comfort while using office chairs. To address the issue that the selection of traditional seat surface material is too subjective and that the prediction effect is poor, an improved sparrow search algorithm (ISSA) optimized least squares support vector machine (LSSVM) method for office chair seat surface material comfort prediction has been proposed. Sparrow Search Algorithm (SSA) was optimized with Sobol sequences, nonlinear inertial weights, and a crisscross optimization algorithm to produce the Improved Sparrow Search Algorithm (ISSA), and then the relevant parameters of the LSSVM algorithm were optimized with the modified algorithm to improve its prediction performance. The prediction accuracy of the ISSA-LSSVM model is as high as 95.75% by combining the body pressure distribution experiments; the root mean square error (RMSE) is 0.29; the goodness of fit (R2) is 0.92; the mean absolute error (MAE) is 0.24; the standard deviation (RSD) is 5.99%. The ISSA-LSSVM model predicts seat surface material comfort more accurately and reliably. This strategy can assist consumers to narrow down their seat surface material choices and even suggest an optimal selection. In this way, it can boost users' pleasure with office chairs, which has great potential for wide application.

Disabled, Chronically Ill, Severe Artist

Disabled, Chronically Ill, Severe Artist Panteha Abareshi (bio) Keywords art, disabled artists, Panteha, Abareshi, installation art, visibility, sickjle cell anemia, chronic illness Click for larger view View full resolution A Lively Corpse 2022 Image description above: A chair with its arms wrapped in bubble wrap and legs wrapped in foam cylinders on a concrete floor, against a white wall. Medical boots, painted with butterflies, are attached with a metal bar to the chair seat, where a square brace faces front. [End Page 681] MY NAME IS PANTEHA ABARESHI; I am an artist currently based in Los Angeles, CA. My work is rooted in my existence as a body with sickle cell zero beta thalassemia, a genetic blood disorder that causes debilitating pain and bodily deterioration that both increase with age. Being a chronically ill body has shaped my experience into one that is extremely and highly isolating. The nuances of disability and chronic illness are lost on the average able-bodied individual, and the marginalization, erasure, and violence that I have endured from it alone is devastating. In combination with my personal notions of gender, racial and sexual identity, I am fully immersed in otherness. There is so little discussion surrounding this, and little to no exploration of these topics in contemporary work, and I aim to push against that lack of representation. In my practice I am warping concrete, physical forms into highly disembodied abstractions. Through my work I aim to discuss the complexities of living within a body that is highly monitored, constantly examined, and made to feel like a specimen. Taking images that are recognizable as human forms, and reducing them to gestural forms is a juxtaposition of my own body's objectification and dissection. Being in hospital for as far back as I can remember, my condition has informed my conceptions of body and self. What are the implications of being told you are unhealthy, fragile, and defective from a young age? Click for larger view View full resolution 2 gallery shots from solo show, This is Not a Body 2022 Hunter Shaw Fine Art, Los Angeles Above: CrutchOpposite: the artist Image description opposite page: The artist, a Black woman with blonde dreadlocks, wears a white sleeveless T-shirt, black pants, and black boots. She is sitting in a blue wheelchair in front of a sunny window, looking at the camera. The floor is gray, the wall is white, and the window is next to a brick column. Above: Installation art of a medical bariatric crutch suspended sideways by red wires and a silver L racket, on a white wall with vents. [End Page 682] Click for larger view View full resolution How does the early and reinforced knowledge of decreased lifespan, and a life of increasingly poor health, pain, and bodily deterioration, influence the relationship between one and their body? Identity becomes a daunting concept when there is a rift formed between one's mind and their body, when the body seemingly functions with a mind of its own, malfunctioning and causing harm. Able-bodied individuals do not realize the supreme privilege in trusting and knowing their own body. Identity as we know it is so highly linked to bodily form and linked to aspects of bodily existence that are taken for granted. I aim to explore these questions, this region of identity, pushing to articulate my own fears, insecurities, and confusions around my illness-identity. My abstracted imaging of my own body is heavily influenced by being so regularly in the hospital, as I am constantly experiencing a very unique form of objectification in which my body is truly treated as a pound of flesh, the vitals that it produces, and the malfunctions it abounds in. In my performance work, I am pushing my own vulnerability and objectification to discuss the realities of mortality and fragility, and the complexities of empowerment in the face of literal powerlessness. Currently, I am contemplating the prosthetic, and the simultaneous abstraction and mechanization of the "body." [End Page 683] Click for larger view View full resolution Above: Performance and installation detail, receipt. Comfort and Care 2019 Opposite: Stills from video/performance work Not Better Yet 2019 VHS...

Eesti kõrkjapõhjaga toolide materjal ja valmistamisprotsess / Wooden chairs with rush seats: material and making process

Wooden chairs with rush seats have been a part of North- and West-European vernacular furniture since at least the 17th century. The same type of chairs with woven seats are represented among the Estonian vernacular chairs as well, but no research has been done on this topic so far. The term “rush seats” (kõrkjapõhjad) has been used in museum collections records as well as archival sources to denote the seats woven of plant material. The aim of the present article is to analyse what plant species have been used for making “rush seats”, how the plant material was prepared for weaving, what the work process was like, and which variations can be found in the patterns of surviving rush seats.
 Our source material includes the rush seat chairs in the Estonian National Museum (ENM) collections and archival sources from the ENM, as well as the Institute of the Estonian Language archive of the Estonian dialects and Finno-Ugric languages (EMSUKA). As the information concerning our research topic in the archival records was rather limited, a considerable part of our research is based on museum artefact analysis, including botanical analysis of the plant material, complemented by a practice-based approach.
 There are 28 rush seat chairs dating from the late 19th to early 20th centuries in the ENM collections. The vernacular plant names used in the archival sources (kõrkjas, luga) do not correspond to the current botanical nomenclature, therefore it remains unclear which plant species were used for weaving chair seats. In 15 chair seats inflorescence were discovered inside the woven plant material, analysis of which identified it as lakeshore bulrush (Schoenoplectus lacustris). In coastal regions, Schoenoplectus tabernaemontanii growing in salt water has also been used. In one case, the seat material is broadleaf cattail (Typha latifolia).
 According to some data in literature, the lake bulrushes were collected for weaving around St John’s Day, i.e. in late June before the inflorescence appeared. However, the inflorescence found inside the seats confirmthat the plants have been, at least partly, collected later, in July. For our own experiments, we have collected bulrushes in early July.
 In the ENM collections, 12 seats have been woven of one-ply bulrush string, and 16 seats are made of two-ply rush cord. The use of one- or two-ply cord may have induced different weaving techniques. Based on comparison with rush weaving traditions in other countries, we suggest that one-ply rush string was made by twisting the plan stems, gradually adding new ones, and at the same time weaving the string around the seat frame. The process of weaving the seat started from the outer corners of the seat frame and then by gradually working towards the centre. All the seats in ENM collection woven with one-ply rush string use this weaving method.
 Preparation of two-ply rush cord started with hand-twisting the plant stems into one-ply string. Likely, a rope-machine was used to then twist the string into two-ply cord. Therefore, while using two-ply cord the weaver had the cord pre-prepared which in turn allowed for the development of a variety of more complicated seat patterns.
 The plants of genus Schoenoplectus are widespread in Estonia. In the past, these plants have been used for a number of purposes, like weaving mats, baskets and bags. The rush seats are described in memoires as comfortable and fairly long-lasting. Hopefully, the present article will provide inspiration to explore the properties and potential uses of this natural material.
 Keywords: chairs, rush seats, weaving, ethnobotany, practice-based artefact study

Design of vibrating chair to introduce limited fatigue to reduce insomnia

Insomnia is a sleep disorder. This leads to decreased efficiency of working during the daytime. It is seen that Insomnia is faced by large number of people some or the other time in their life. People with disabilities also face sleep issue for larger period.Vibrations induce physical fatigue.Vibrations with proper parameters like frequency of vibration & amplitude of vibration may reduce insomnia to a large extent. This may be by inducing limited physical fatigue in these people by subjecting their body to vibrations.The aim of this research work was to review the related research work & design a vibrating chair with the proper parameters, frequency & amplitude of vibration, for reduction of insomnia.A frequency of 5 Hz & amplitude of 7.5 mm has been finalized for this vibrating chair. In this paper, design of a vibrating chair has been presented. Considering the use of this chair at home, the components have been chosen/ designed to suit the same. This vibrating chair consists of an AC motor mounted below the seat of chair. This motor is geared motor which reduces the speed of the motor shaft from 1440 to 300 rpm through worm & worm wheel. The motor input power is only 150 W. The vibrations produced are due to the falling of follower which is fixed to the bottom side of the chair. A model of the designed vibrating chair has been prepared using CATIA V5 R19 software. This vibrating chair may be used for about 20 to 30 min daily by the people who are facing insomnia.

Monkeypox virus contamination in an office-based workplace environment

Monkeypox virus contamination in an office-based workplace environment

The impact of seat height on 1-min sit-to-stand test performance in COPD: a randomised crossover trial.

Study questionIs there a difference in the number of repetitions in the 1-minute sit-to-stand (1MSTS) test using an individually adapted seat height to 90° knee flexion (1MSTSIND), compared with the commonly used standard chair seat height of 46 cm (1MSTSSTD), in people with COPD?MethodsWe conducted a single-centre, single-blinded, randomised crossover trial in people with COPD between August 2020 and March 2021 at a specialised rehabilitation clinic in Switzerland. After a learning 1MSTS test, all participants performed two 1MSTS tests in random order on consecutive days. Participants were blinded, as they did not receive detailed information on the testing protocols.Results49 individuals with COPD (47% female) participated. In a regression model adjusted for sequence period and subject, 1MSTS test performance was lower on 1MSTSIND compared to 1MSTSSTD (−0.78 repetitions, 95% CI −1.47 to −0.11). In a second regression model additionally including the knee angle and an interaction term (1MSTSIND×knee angle), the interaction term was significant: 0.18 (95% CI 0.05 to 0.30). The limits of agreement were between −5.5 and 4 repetitions.ConclusionAlthough we observed a statistically significant difference between 1MSTSIND and 1MSTSSTD on a population level, the difference is negligible. Further studies may be needed to determine whether individual adaptation of seat height is needed for very tall or short people to ensure a valid assessment of 1MSTS test performance in COPD.

Optimization of All-Textile Capacitive Sensor Array for Smart Chair

All-textile capacitive sensor arrays made of a polyurethane foam, fabric and electrically-conducting yarn were fabricated for a ‘smart chair’. Polyurethane foam slab that functioned as a dielectric medium was encased between two pieces of commercially available fabric. The electrically-conducting yarn was used to embroider the capacitor electrodes on both fabric pieces. The completed sensor arrays were investigated under normal compressive load with the targeted pressure range of 2 to 30 kPa for the chair seat and 2 to 8 kPa for the backrest. The sensor capacitance versus normal compressive load exhibited a load/unload hysteresis for all sensor arrays. The hysteresis was modelled with sigmoid function and much narrower hysteresis was observed when all sensors were loaded simultaneously, as opposed to their individual loading, allowing development of a phenomenological model for the former. Among the studied sensor arrays, the array with dimensions of 30 cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times 30$ </tex-math></inline-formula> cm made of a 10-mm-thick polyurethane foam with density of ~18.6 kg/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> was the most suitable for the following reasons: (a) unloaded sensor capacitance was ~2.7 pF, (b) the sensor location did not affect its response, (c) ~10 kg load applied across individual sensor raised its capacitance by ~12 pF, and (d) 60 kg load applied uniformly across the whole sensor array increased the capacitance by ~5 pF. During the compression of the individual sensors the top fabric affected the sensor’s electro-mechanical response and elastic fabric would be favored for applications with non-uniform pressure distribution.

Chair Development on the Basis of Body Pressure Distribution—A Research Effort*

Abstract Surveys and studies show that more and more employees perform high- or low-skilled white-collar work predominantly in sitting postures. Therefore, comfortable sitting plays an important role in reducing the risk of musculoskeletal disorders and other harmful effects. Research efforts focus on reducing these risks by designing ergonomic chairs with multiple adjustment possibilities, allowing the chair to fit to the user's body shape or assuring a dynamic seating where the user's lower body is in continuous movement. This article summarizes the results of a research effort that evaluated the effect of several factors on sitting comfort based on body pressure distribution. The effects of foam elasticity, foam layer arrangement order, and seat support elasticity were investigated as well as the chair seat type (kneeling chair, saddle chair). Results were used to determine the optimal chair cushion including the layered foam system and seat support type. On the basis of our findings a new ergonomic chair was developed combining the advantages of static and dynamic sitting.

Development of Automatic Chair Transport System - Chair Recognition and Approach Strategy –

In schools and other educational institutions, there are many instances that require the arrangement of chairs depending on the required purpose, such as a class or event. Some chairs are on casters; however, educational institutions typically use stacking or folding chairs. Although effective in terms of storage, these must be lifted by hand during transportation, increasing the burden on the workforce. While automation of baggage transport in warehouses has improved significantly, little attention has been paid to the automation of chair transport. Despite the demand and the fact that self-propelled chairs have already been developed, automatic transport of chairs without casters has never been reported. In this study, we constructed an automatic chair-transport system using an omnidirectional mobile robot and focused on a stacking chair that allowed the robot to position itself underneath. The developed system utilizes the image of the seat and frame pipe of the stacking chair to estimate the chair’s position and direction with respect to the robot. Once the robot has positioned itself under the chair, the chair is lifted and transported using a lifter device attached to the robot.

Ergonomic Design of Classroom Furnitures: Evaluation of Comfortability and Musculoskeletal Disorders

Background: Anthropometric studies are essential in furniture design to ensure comfortability and improved productivity of the users. Methods: Anthropometry of 407 from a population of 5601 students, and classroom furniture at Kwame Nkrumah University of Science and Technology were evaluated. Student’s comfortability and reported musculoskeletal disorders (MSDs) in using the furniture were assessed with two questionnaires. Participants who volunteered for the study were randomly selected and had no previous history of MSDs. Descriptive statistics of the collected data were analyzed using SPSS software. Results: The participant's aged ranged from 17 to 28 years, and mostly were female (61%). The fitness between student’s anthropometry and classroom furniture included underneath table height for the imported plastic furniture and chair seat depth and width, as well as underneath table height for the locally manufactured wooden furniture. We observed high incidence of MSDs, including upper back (71.40%), lower back (58.30%), neck (51.90%), joint (39.10%), shoulder (32%), knee (25.20%), and wrist (22.60%) pain. The prevalence of MSDs were higher in women than men. The majority of the students were uncomfortable with using the furnitures, and only 6.6% reported comfortable experience. Conclusion: Recommended dimensions for ergonomically designed furniture have been proposed to reduce MSDs in the students. It would improves student’s health, and promote comfortability.

Perancangan kursi duduk-berdiri berdasarkan pendekatan antropometri di PT. Otscon Safety Indonesia

The problem of incompatibility between facilities and humans is still found, where the impact is the insecurity of worker safety, increased workload, disruption of work processes, and their effects on workers' conditions. PT. Otscon Safety Indonesia is a manufacturing company that manufactures automotive components called the Lever Parking Brake. The company has an assembly work station called Button Release Assy, where the work is done in a standing work position, so that operators will quickly feel fatigue from working in a standing position.This study aims to design a Sit-and-Stand Chair, so that operators working at the button release work station do not experience fatigue quickly. The design of the Sit-and-Stand Chair is based on the Anthropometric approach to create an ergonomic chair. The size of the chair is determined based on the results of the percentile calculation of body dimensions, where the body dimensions used are the hip width to find the diameter of the seat cushion and hip height and the vertical height of the chair from the floor. The results showed that the chair seat diameter from the 95th percentile was ∅35.4 cm and the height of the chair from the floor vertically from the 5th percentile was 83.4 cm

IoT Device for Sitting Posture Classification Using Artificial Neural Networks

Nowadays, the percentage of time that the population spends sitting has increased substantially due to the use of computers as the main tool for work or leisure and the increase in jobs with a high office workload. As a consequence, it is common to suffer musculoskeletal pain, mainly in the back, which can lead to both temporary and chronic damage. This pain is related to holding a posture during a prolonged period of sitting, usually in front of a computer. This work presents a IoT posture monitoring system while sitting. The system consists of a device equipped with Force Sensitive Resistors (FSR) that, placed on a chair seat, detects the points where the user exerts pressure when sitting. The system is complemented with a Machine Learning model based on Artificial Neural Networks, which was trained to recognize the neutral correct posture as well as the six most frequent postures that involve risk of damage to the locomotor system. In this study, data was collected from 12 participants for each of the seven positions considered, using the developed sensing device. Several neural network models were trained and evaluated in order to improve the classification effectiveness. Hold-Out technique was used to guide the training and evaluation process. The results achieved a mean accuracy of 81% by means of a model consisting of two hidden layers of 128 neurons each. These results demonstrate that is feasible to distinguish different sitting postures using few sensors allocated in the surface of a seat, which implies lower costs and less complexity of the system.