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The effect of wrist rests and forearm support during keyboard and mouse use
Abstract
Supporting the forearm on the work surface during keyboard operation may increase comfort, decrease muscular load of the neck and shoulders, and decrease the time spent in ulnar deviation. Wrist rests are used widely in the workplace and are more commonly being incorporated in keyboard design. The aim of this study was to examine the effect of wrist rest use on wrist posture during forearm support. A laboratory based, experimental study was conducted (subjects n=15) to examine muscle activity and wrist postures during keyboard and mouse tasks in each of two conditions; wrist rest and no wrist rest. There were no significant differences for right wrist flexion/extension between use of a wrist rest and no wrist rest for keyboard or mouse use. Left wrist extension was significantly higher without a wrist rest than with a wrist rest during keyboard use (df=14; t=2.95; p=0.01; d=0.38). No differences with respect to use of a wrist rest were found for the left or right hand for ulnar deviation for keyboard or mouse use. There were no differences in muscle activity between the test conditions for keyboard use.Relevance to industryWrist rests are used widely in the workplace and are more commonly being incorporated in keyboard design. Use of a wrist rest in conjunction with forearm support when using a conventional desk does not appear to have any impact on wrist posture or muscle activity during keyboard use.
... There were a total of 1,061 working subjects in the 11 studies included, with ages ranging from 16 to 67 years. The studies were conducted with working subjects from digitalization video terminals (Marklin and Simoneau, 2001;Schmid et al., 2015;Cook et al., 2004;Galinsky et al., 2007), call centers (Street et al., 2003), engineers (Conlon et al., 2008), dentists (Nemes et al., 2013), nurses (Lincoln et al., 2002), and individuals exposed to highly repetitive manual tasks involving manual force or (Sundstrup et al., 2014) even vibration (Jetzer et al., 2003;Charpe and Kaushik, 2012). The main characteristics of the included studies are summarized in Table 7. ...
... When analyzing specific intervention categories, it was observed that ergonomic interventions associated with modifications on the keyboard, mouse, and wrist rest did not have the desired effect on the evaluated conditions (Marklin and Simoneau, 2001;Schmid et al., 2015;Conlon et al., 2008;Cook et al., 2004). Nevertheless, positive results were observed when ergonomic interventions were combined or compared with education in aspects such as the application of ergonomic principles in postural hygiene, also including topics regarding participative ergonomics, the definition of musculoskeletal disorders, co-responsibility of working subjects, changes in usual conducts, and the importance of exercise and work breaks (Street et al., 2003;Lincoln et al., 2002). ...
... The authors agree on the difficulty in finding high-quality studies as is also shown in this review. There were only three common papers between both reviews (Conlon et al., 2008;Cook et al., 2004;Galinsky et al., 2007). ...
Carpal Tunnel Syndrome (CTS) is one of the most frequently occurring musculoskeletal disorders of the upper limbs. Strategies for preventing CTS in the workplace include interventions such as ergonomics, education, exercise, physical therapy, and occupational health. The purpose of this study was to provide a general overview based on the review of scientific literature regarding strategies used for preventing CTS in working populations. From September to October 2018, the MEDLINE, PUBMED, EMBASE and SCOPUS (1990 to December 2017) databases were searched for evidence. The risk of bias assessment in the selected papers was evaluated using the criteria recommended by The Cochrane Handbook and the methodological quality of the included studies was evaluated using Standard Quality Assessment Criteria for Evaluating Primary Research Papers from a Variety of Fields. A total of 11 studies were included in the present review. A total of 1,061 subjects participated in the studies. The quality of the included studies was limited in three studies, appropriate in three studies, good in three studies, and strong in two studies. The overall results suggest a mixed level of evidence of the effect of applying strategies for preventing CTS in the workplace. The bias assessment was primarily due to incomplete result data, selective reporting of results, and blinding. In this review, interventions focused on the modification or change of accessories (keyboard, mouse, wrist rest, and the overall workstation), education in ergonomics, exercise, and physical therapies, among others, were analyzed. The findings of this review show different possibilities when choosing an intervention strategy for the workplace. However, it was challenging to analyze each of the papers owing to the heterogeneity of the studies included.
... The wrist may act as a fulcrum and the addition of specific joint space degrees of freedom there in tremor tasks reduces the degree of oscillation of the index finger (Morrison & Newell, 2000). Forearm support has been demonstrated to have biomechanical advantages to hand or wrist support in computer operators (Aarås et al., 1998, Aarås et al., 2001Cook et al., 2004aCook et al., , 2004bLee & Huang, 2006). Support at the level of the forearm rather than just hand support may offer advantages for the surgeon and also computer operators. ...
... Forearm supports compared to hand supports have demonstrated ergonomic advantages for computer operators in passive and dynamic activities (Aarås et al., 2001;Cook et al., 2004aCook et al., , 2004bLee & Huang, 2006). Forearm supports proximal to the wrist have demonstrated desirable effects including decreased discomfort and decreased muscular load of the neck, shoulders, forearm, and upper arm muscles for computer operators (Aarås et al., 1998, Aarås et al., 2001Cook et al., 2004aCook et al., , 2004bLee & Huang, 2006). ...
... Forearm supports compared to hand supports have demonstrated ergonomic advantages for computer operators in passive and dynamic activities (Aarås et al., 2001;Cook et al., 2004aCook et al., , 2004bLee & Huang, 2006). Forearm supports proximal to the wrist have demonstrated desirable effects including decreased discomfort and decreased muscular load of the neck, shoulders, forearm, and upper arm muscles for computer operators (Aarås et al., 1998, Aarås et al., 2001Cook et al., 2004aCook et al., , 2004bLee & Huang, 2006). Forearm support, rather than just hand support, may provide the surgeon ergonomic advantages. ...
Objective
Surgeon tremor was measured during vitreoretinal microscopic surgeries under different hand support conditions.
Background
While the ophthalmic surgeon’s forearm is supported using a standard symmetric wrist rest when operating on the patient’s same side as the dominant hand (SSD), the surgeon’s hand is placed directly on the patient’s forehead when operating on the contralateral side of the dominant hand (CSD). It was hypothesized that more tremor is associated with CSD surgeries than SSD surgeries and that, using an experimental asymmetric wrist rest where the contralateral wrist bar gradually rises and curves toward the patient’s operative eye, there is no difference in tremor associated with CSD and SSD surgeries.
Methods
Seventy-six microscope videos, recorded from three surgeons performing macular membrane peeling operations, were analyzed using marker-less motion tracking, and movement data (instrument path length and acceleration) were recorded. Tremor acceleration frequency and magnitude were measured using spectral analysis. Following 47 surgeries using a conventional symmetric wrist support, surgeons incorporated the experimental asymmetric wrist rest into their surgical routine.
Results
There was 0.11 mm/s ² (22%) greater ( p = .05) average tremor acceleration magnitude for CSD surgeries (0.62 mm/s ² , SD = 0.08) than SSD surgeries (0.51 mm/s ² , SD = 0.09) for the symmetric wrist rest, while no significant ( p > .05) differences were observed (0.57 mm, SD = 0.13 for SSD and 0.58 mm, SD = 0.11 for CSD surgeries) for the experimental asymmetric wrist rest.
Conclusion
The asymmetric wrist support reduced the difference in tremor acceleration between CSD and SSD surgeries.
... Extreme heat in organizations creates mental depression and affects work performance (Clark, 2002). Extreme cold in organization on the other hand could bring about absenteeism and disturb one's mental ability (Smith et al., 2000). ...
... This finding supports Tarcan et al. (2004) who stated that ergonomic workstation could minimize the stress problem at the workplace. In addition to this statement, Clark (2002) and Leaman (1995) also view that the extreme organizational temperature research concludes that good lighting system could minimize the stress outcomes at the workplace and it supports several scholars' research findings (Sutton & Rafaeli, 1987;Aaras et al., 2001;Leather et al., 2003;Wojcikiewicz, 2003). H4 supports the findings of Melamed et al. (1992), Leather et al. (2003) and Fairbrother & Warn (2003) where they emphasized that acoustic system plays important role in minimizing stress problem at the workplace. ...
... Shiftwork also must be given attention as several literatures pointed out that it relates closely to work stress at the workplace (Tasto et al., 1978;Costa, 2003;Kundi, 2003). The finding in H4 also supports Savery and Luks (2000), Ahasan (2002), Clark (2002), Tucker (2003, and Iacovides et al. (2003). They make a point that long working hour without proper rest would increase depression and lead to stress. ...
Literatures show that work stress has been a major workplace problem now as compared to the past and it has become among the major causes that contribute to workplace accidents. The occurrence of work stress is quite rampant in the manufacturing organizations which involved blue collar workers. The literatures reveal that poor ergonomics workstation environment is among the major contributor to the work stress problems. Thus, this study aims to examine the relationships between ergonomics workstation factors and the work stress outcomes. Five hundred samples of production operators were derived from eleven manufacturing electronics organizations which were registered with Malaysian International Chamber of Commerce and Industry (MICCI) by using proportionate stratified random sampling. Questionnaires were used for the data collections process. The major finding shows that ergonomically designed workstation is an important strategy in minimizing the work stress outcomes in organizations. Through the multiple regression analysis, each ergonomics workstation factor and component collectively have significant relationship with the work stress outcomes. These findings have been supported by the Pearson correlation analysis which shows that all ergonomics workstation factors have high significant correlation with the work stress outcomes. The multiple regression analysis shows health, work area design, shiftwork, humidity system and working hours factors have significant relationship with work stress outcomes. Furthermore, ergonomics workstation components proved that the human and environment factors have significant relationship with the work stress outcomes. The person-environment fit (P-E fit) and the effectiveness of training program can minimize the work stress outcomes which are caused by poor ergonomics of workstation factors.
... Keadaan situasi di United Kingdom pula menunjukkan terdapat 415,000 individu percaya mereka mengalami stres yang telah menyumbang anggaran sebanyak 11.4 juta kehilangan hari bekerja bagi tahun 2008/09 (Smith, Chaplin & Wadsworth, 2012). Menurut Clark (2002), tuntutan pampasan yang berkaitan dengan masalah stres di tempat kerja dan kecederaan di United Kingdom telah meningkat sebanyak 33 peratus menjelang tahun 2000. Kesemua masalah yang melibatkan stres ini telah mengakibatkan ekonomi United Kingdom kerugian £7 billion kesan daripada kekurangan pengeluaran, bayaran perubatan dan caj kesihatan (Clark, 2002). ...
... Menurut Clark (2002), tuntutan pampasan yang berkaitan dengan masalah stres di tempat kerja dan kecederaan di United Kingdom telah meningkat sebanyak 33 peratus menjelang tahun 2000. Kesemua masalah yang melibatkan stres ini telah mengakibatkan ekonomi United Kingdom kerugian £7 billion kesan daripada kekurangan pengeluaran, bayaran perubatan dan caj kesihatan (Clark, 2002). ...
... Bagi pengguna komputer pula, aduan yang berkaitan dengan kesakitan mata adalah paling popular (Benton, 1998;Fagarasanu & Kumar, 2003;Blatter & Bongers, 2002;Cook, Burgess-Limerick & Papalia, 2004;Gustafsson, 2003;Jensen, Finsen, Sogaard & Christensen, 2002;Kaderfors & Laubli, 2002;Cooper & Kleiner, 2001;Chao, 2001). Tanda-tanda kesakitan mata adalah seperti mata merah, berair, dan daya penglihatan yang semakin merosot. ...
ABSTRACT: Work stress problems should not be taken lightly by the organization and it is a global issue that gives huge impact on organizational productivity. Stress is also a major issue in terms of occupational safety and health. Literature review clearly shows that stress at the workplace is commonly associated with cost and organizational productivity. Actually, stress at the workplace is not a new phenomenon in working environment. It exists in every organization and no one could evade from stress. Stress at the workplace issues get major interest in Japan and United States organizations since the problem is strongly related to overall organizational performance. In England and Wales, stress at the workplace is among top three categories of the largest disease caused by working environment. World Health Organization (WHO) believes that stress at the workplace problem will become a major threat to human health by year 2020. Stress is not an
e-BANGI Vol 8, No. 1 (2013):041-059
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occupational problem that should be taken lightly. Although every employee worldwide will experience this problem, but the question is how they can survive when stress become uncontrolled. This issue should be given serious attention by every organization in the world. Furthermore, technological change, social and discontinuation in the employment sector will make this problem a serious global issue.
Keywords: Stress, global, health, working environment
ABSTRAK: Masalah stres di tempat kerja seharusnya tidak dipandang ringan oleh organisasi dan ia merupakan isu global yang memberi impak yang besar terhadap produktiviti organisasi. Stres juga merupakan isu utama dalam aspek keselamatan dan kesihatan pekerjaan. Tinjauan literatur jelas menunjukkan bahawa masalah stres di tempat kerja sering dikaitkan dengan kos dan produktiviti organisasi. Sebenarnya, stres di tempat kerja bukanlah satu fenomena baru dalam persekitaran pekerjaan. Ia wujud dalam setiap organisasi dan tiada siapa boleh mengelak daripada stres. Isu stres di tempat kerja ini mendapat perhatian utama organisasi-organisasi di Jepun dan Amerika Syarikat kerana masalah ini amat berkaitan dengan prestasi organisasi keseluruhannya. Di England dan Wales, stres di tempat kerja merupakan antara 3 kategori penyakit terbesar yang disebabkan oleh persekitaran pekerjaan. Pertubuhan Kesihatan Sedunia (WHO) menjangkakan bahawa masalah stres di tempat kerja akan menjadi ancaman utama kepada tahap kesihatan manusia menjelang tahun 2020. Stres bukanlah masalah pekerjaan yang perlu dipandang remeh. Walaupun setiap pekerja di seluruh dunia akan mengalami masalah ini, namun persoalannya, mampukah pekerja bertahan apabila stres menjadi tidak terkawal. Inilah isu yang perlu diberi perhatian serius oleh setiap organisasi di dunia. Tambahan pula, perubahan teknologi, sosial dan ketidaksinambungan dalam sektor pekerjaan menjadikan masalah stres sebagai isu global yang serius.
... Concentrons nous maintenant sur la partie (A)- Figure 2. 5. Nous pouvons constater que la différence entre les seuils n'est pas négligeable. ...
... Plus précisément, le classement des activités de la plus à la moins à risque de fatigue musculaire est donné par cet ordre : "TextH", "Text", "Puzl", "Sol", "Str". Ces résultats corroborent ceux de la littérature [4,5], où les auteurs ont montré que les activités utilisant le clavier génèrent une sollicitation du muscle trapèze supérieur aux activités utilisant la souris. Notre travail montre que l'analyse de la variabilité du signal, qui n'a pas été étudiée par ces auteurs, confirme ces résultats. ...
Cette thèse traite de la problématique de la détection de rupture dans le cadre séquentiel où le signal est supposé être observé en temps réel et le phénomène passe de son état de départ "normal" à un état post-changement "anormal". Le défi de la détection séquentielle est de minimiser le délai de détection, soumis à une limite tolérable de fausse alarme. L'idée est de tester séquentiellement l'existence d'une rupture par l'écriture récursive de la statistique de détection en fonction du score, qui remplace le Log-Likelihood Ratio lorsque la distribution des données est inconnue. La procédure de détection repose ainsi sur une statistique récursive, un seuil de détection et une règle d'arrêt. Dans un premier travail, nous considérons la statistique score-CUSUM et proposons d'évaluer la performance de détection de certains seuils de détection. Deux seuils sont issus de la littérature, et trois nouveaux seuils sont construits par une méthode basée sur la simulation: le premier est constant, le second instantané et le troisième est une version dynamique "data-driven" du précédent. Nous définissons rigoureusement chacun des seuils en mettant en évidence les différentes notions du risque de fausse alarme contrôlé suivant le seuil. Par ailleurs, nous proposons une nouvelle règle d'arrêt corrigée pour réduire le taux de fausse alarme. Nous effectuons ensuite une étude de simulation pour comparer les différents seuils et évaluer la règle d'arrêt corrigée. Nous constatons que le seuil empirique conditionnel est le meilleur pour minimiser le délai de détection tout en maintenant le risque toléré de fausse alarme. Cependant, sur des données réelles, nous recommandons d'utiliser le seuil data-driven car c'est le plus simple à construire et à utiliser pour une implémentation pratique. Dans la seconde partie, nous appliquons notre méthodologie de détection data-driven sur des signaux physiologiques, à savoir des signaux temporels enregistrés au niveau du faisceau supérieur du trapèze de 30 sujets effectuant différentes activités bureautiques. La méthodologie est sujet-activité dépendante; elle inclut l'estimation on-line des paramètres du signal et la construction du seuil data-driven sur le début du signal de chaque activité de chaque sujet. L'objectif était d'identifier des changements de régimes au cours d'une activité afin d'évaluer le niveau de sollicitation du muscle et la variabilité du signal EMG, qui sont liés à la fatigue musculaire. Les résultats obtenus ont confirmé l'aisance de notre méthodologie et la performance et praticité du seuil data-driven proposé. Par la suite, les résultats ont permis la caractérisation de chaque type d'activité en utilisant des modèles mixtes.
... The lateral position of the mouse typically puts the user's shoulder in an abducted and externally rotated position, with the arm in forward flexion and the wrist in extension, ulnar deviation and pronation (Cook, Burgess-Limerick, & Papalia, 2004). This is thought to increase pressure within the carpal tunnel, impair nerve function, increase muscular stress, such as static loading in the antigravity muscles, and predispose to subsequent myotendinous inflammation. ...
... Research has also shown that the abduction of the arm seen with the lateral placement of the mouse may be related to musculoskeletal symptoms (Cook et al., 2004). The increased activity of sub-occipital muscles and a requirement for a significant amount of hand-eye coordination and strenuous wrist and shoulder postures associated with conventional computer mice may be avoidable with the placement of a roller-style mouse just below the keyboard. ...
Prolonged use of a standard mouse is associated with musculoskeletal symptoms. This review provides professionals with in-depth analysis of the literature regarding the evidence behind the use of alternative computer mouse designs and their ability to reduce discomfort in mouse users, in addition to the potential effect of ergonomics training and forearm supports. Multiple data bases were searched by independent researchers to identify 17 high-quality controlled trials including varieties of acceptable mouse designs (vertical, slanted, upright, roller bar, biofeedback and others). Methodological quality of these studies were assessed by independent raters utilizing the PEDro quality assessment scale and the Cochrane Risk of Bias (ROB) scale, and the results revealed that included studies were of moderate quality (5–6/10) and had some intrinsic ROB. It is concluded that there is moderate quality of evidence to support the use of alternative mouse designs to reduce discomfort, promote posture and decrease unnecessary muscle activation, especially if accompanied by appropriate ergonomic training. However, standard mouse still offers appropriate users preference levels. Hence, the consensus is that, mouse selection and purchase should be an individualized process based on individual needs and work demands and that there is no universal model that works well with everyone. © 2018, © 2018 The Author(s). This open access article is distributed under a Creative Commons Attribution (CC-BY) 4.0 license.
... Using a height-adjustable desk, the desk was placed at a height that had allowed the subjects to maintain 90° of elbow flexion [21], and a 15-inch HP 630 laptop PC (Hewlett-Packard Company, Palo Alto, CA, USA) was used for typing purposes. ...
... Since the weight of the head is about 1/7 of the body and many people have their head and neck postures fixated during prolonged use of computers with repetitive use of the keyboard, excessive load is applied onto to the shoulders, which subsequently causes pain. Cook et al. [21] stated that relaxation of the cervical extensor muscles is important for the correction of a forward head posture. Villanueva et al. [28] reported that head posture has an influence on trunk muscle activity while Andersson et al. [29] stated that elector spinae muscle activity is reduced with the round-back sitting position. ...
... For example, chairs used by workers to perform their tasks fulfil three principal functions: increasing individual effectiveness; minimizing fatigue and stress at the workplace; and fitting the body posture (Wojcikiewicz 2003). However, adjustable chairs and chairs with armrests will help to minimize strains on the neck, shoulder and arm muscles (Cook et al. 2004). An ergonomic chair will not only allow employees to perform their tasks, but also aids in the quicker completion of tasks and, most importantly, minimizes work stress (Beckett 1995). ...
... Literature states that ergonomic chairs and comfortable work areas can minimize work stress (Sutton & Rafaeli 1987;Beckett 1995;Aaras et al.2001;Cook et al. 2004). However, the result for H 3 is not significant. ...
The present study explores ergonomic workstation factors to explain work stress outcomes. Proportionate stratified random sampling method is utilized to collect data from 500 production operators. The production operators are employees of 11 manufacturing electronics organizations that joined Malaysian International Chamber of Commerce and Industry (MICCI). The data samples are based upon self-administered questionnaires. Following data analysis, ergonomically designed workstations are proven to be a significant strategy to help organizations minimize work stress outcomes. Additionally, the multiple regression analysis shows that ergonomic workstation element collectively has significant relationship with work stress outcomes.
... For a chair to be ergonomic, it has to have at least vertically adjustable. The ergonomic chair will affect the workers performance through minimization of fatigue and stress (Cook et al., 2004). ...
... For the hypothesis 1, 5 and 6, the regression analysis support the research hypothesis, therefore we can conclude that there is a significant relationship for three variables (chair/office seating, working hours and humidity) and the outcomes of work stress. The result of hypothesis 1 supported the statements of Cook et al., (2004). The hypotheses 5 result supported Iacovides et al. (2003) and Clark (2002). ...
... Tempat duduk atau kerusi yang digunakan oleh pekerja untuk melakukan tugas mereka mempunyai tiga matlamat utama, iaitu meningkatkan keberkesanan individu, meminimumkan keletihan dan stres di tempat kerja, serta menyesuaikan bentuk badan (Wojcikiewicz, 2003). Tekanan terhadap bahagian leher, otot bahu dan lengan boleh diminimumkan jika menggunakan kerusi yang boleh dilaras dan mempunyai tempat letak tangan (armrests) (Cook et al., 2004). Reka bentuk kerusi yang ergonomik, bukan sahaja membolehkan pekerja menyempurnakan tugas mereka tetapi dapat membantu mempercepatkan pelaksanaan tugas tersebut dan meminimumkan stres di tempat kerja (Beckett, 1995). ...
... Penemuan dalam hipotesis 3 juga bercanggah dengan pendapat Sutton dan Rafaeli (1987), Beckett (1995), Aaras et al. (2001) dan Cook et al. (2004). Mereka menegaskan bahawa rekabentuk kerusi yang ergonomik dan ruang kerja yang selesa dapat meminimumkan masalah stres di tempat kerja. ...
Abstrak Penyelidikan ini bertujuan mengkaji perhubungan di antara faktor stesen kerja ergonomik dan akibat stres. Sampel seramai lima ratus operator pengeluaran telah dipilih daripada sebelas organisasi perkilangan elektronik yang berdaftar dengan Malaysian International Chamber of Commerce and Industry (MICCI) dengan menggunakan kaedah persampelan rawak berstrata berkadaran. Kaedah soal selidik telah digunakan dalam proses pengumpulan data kajian ini. Penemuan utama menunjukkan reka bentuk stesen kerja ergonomik merupakan strategi penting dalam meminimumkan akibat stres dalam organisasi. Analisis korelasi Pearson mengukuhkan kenyataan ini dengan menunjukkan kesemua faktor stesen kerja ergonomik mempunyai kekuatan hubungan yang signifikan dengan akibat stres. Analisis regresi linear berbilang menunjukkan faktor kesihatan, reka bentuk ruang kerja, kerja syif, sistem pengudaraan dan tempoh masa bekerja mempunyai hubungan signifikan dengan akibat stres. Komponen stesen kerja ergonomik pula membuktikan bahawa faktor manusia dan persekitaran mempunyai hubungan yang signifikan dengan akibat stres.
Kata kunci :
Ergonomik; stres; operator pengeluaran; stesen kerja; organisasi multinasional
Abstract. This study aims to examine the relationship between ergonomics workstation factors and the work stress outcomes. Five hundred samples of manufacturing operators were derived from eleven manufacturing electronics organizations which were registered with Malaysian International Chamber of Commerce and Industry (MICCI) by using proportionate stratified random sampling. Questionnaires were used for the data collection process. The major finding shows that ergonomically designed workstation is an important strategy in minimizing the work stress outcomes in organizations. These findings have been supported by the Pearson correlation analysis which shows that all ergonomics workstation factors have high significant correlation with the work stress outcomes. The multiple regression analysis shows health, work area design, work shift, humidity system and working hours factors have significant relationship with work stress
outcomes. Furthermore, ergonomics workstation components proved that the human and environment factors have significant relationship with the work stress outcomes.
Keywords :
Ergonomics, stress, manufacturing operator, workstation, multinational organization .
... The use of arm supports during keyboard use has been shown to reduce neck and shoulder muscle activity and reduce musculoskeletal discomfort in the neck, shoulders, wrist, and arms (Conlon et al., 2008; Aaras et al., 1997; Lintula et al., 2001; Delisle et al., 2006; Rempel et al., 2011). Forearm support use has been associated with a decrease in wrist extension and ulnar deviation (Cook et al., 2003; Lintula et al., 2001; Cook et al., 2004), though the use of wrist rests has been associated with increased carpal tunnel pressure and less postural variability (Cook et al., 2003). Most previous research has been conducted for arm support use during keyboarding rather than mousing. ...
... The use of arm supports during keyboard use has been shown to reduce neck and shoulder muscle activity and reduce musculoskeletal discomfort in the neck, shoulders, wrist, and arms (Conlon et al., 2008; Aaras et al., 1997; Lintula et al., 2001; Delisle et al., 2006; Rempel et al., 2011). Forearm support use has been associated with a decrease in wrist extension and ulnar deviation (Cook et al., 2003; Lintula et al., 2001; Cook et al., 2004), though the use of wrist rests has been associated with increased carpal tunnel pressure and less postural variability (Cook et al., 2003). Most previous research has been conducted for arm support use during keyboarding rather than mousing. ...
The use of forearm and palm supports has been associated with lower neck and shoulder muscle activity as well as reduced musculoskeletal discomfort during keyboard use, however, few studies have investigated their effect during computer mouse use. Eight men and eight women completed several computer mousing tasks in six arm support conditions: Forearm Support, Flat Palm Support, Raised Palm Support, Forearm + Flat Palm Support, Forearm + Raised Palm Support, and No Support. Concurrently, an infrared three-dimensional motion analysis system measured postures, six-degree-of-freedom force-torque sensors measured applied forces & torques, and surface electromyography measured muscle activity. The use of forearm support compared to the no support condition was significantly associated with less shoulder muscle activity & torque, and the raised palm support was associated with less wrist extension. Forearm supports reduced shoulder flexion torque by 90% compared to no support. The use of either support also resulted in lower applied forces to the mouse pad. Participants reported less musculoskeletal discomfort when using a support. These results provide recommendations for office workstation setup and inform ergonomists of effective ways to reduce musculoskeletal exposures.
... 2,20,21 Negative effects of prolonged office works are not limited to the hand/wrist, and several studies also reported that individuals with more than 6 h per day of computer use were strongly susceptible to disorders in different parts of the upper body regions, e.g. the neck, shoulder, elbow, arm, and wrist/hand. 22 Specifically, prolonged mouse use has been shown as a significant ergonomic risk factor which contributes to sustained muscle load and non-neutral postures J Health Sci Surveillance Sys July 2023; Vol 11; No 3 such as extreme ulnar deviation, wrist extension, and forearm pronation. 2,5,15,[23][24][25] For better understanding of how prolonged use of the mouse contributes to MSDs, a closer look is needed at the mouse from a design perspective. ...
Background: Musculoskeletal disorders in the upper extremities
are common among computer users. This study aimed to assess
the effect of mouse pad angle on forearm muscles activity
and upper limb discomfort.
Methods: This is an experimental research design. The mouse
pad was set at 0, 10, 20, and 30 degrees of forearm supination.
Ten subjects performed an identical text editing task with a mouse
in each pad position. The electrical activity of the selected forearm
muscles was recorded with surface electrodes. 10-point rating
scales were used for assessing perceived discomfort.
Results: Extensor Carpi Radialis had the lowest mean of
Electromyography (EMG) values in the 0° slanted pad (5.94),
and the highest values were associated with Pronator Quadratus
in 0-degree slanted pad (22.29). The highest and the lowest mean
(SD) of the users’ upper limb discomfort were 3.70 (1.63) and 1.90
(1.28) in 30° and 10° slanted pads, respectively.
Conclusion: Using slanted mouse pads could be helpful and
practical tool for office workers to keep more neutral wrist/hand
positions.
... Tarcan et al (2004) posit that body posture can lead to work stress, for example, prolonged static movement can reduce body flow to tendons, which is likely to cause fatigue and strain (Zafir et al 2003 However, adjustable chairs and chairs with armrests will help to minimize strain on the neck, shoulder and arm muscles (cook, Burgess-Limerick & Papalia 2004). An ergonomic chair will not only allow employees to perform their tasks, and most importantly, minimizes work stress. ...
Implementing ergonomic solutions can make employees more comfortable and increase productivity. This study focused on examining the impact of ergonomics on stress reduction in Globacom and MTN Organizations. The study adopted a survey research approach in its design. The study was made up of a sample size of 95 samples drawn from a population of 109 using the Taro Yamane formula. The study used the simple percentage, Pearson product-moment correlation, and simple regression with the aid of SPSS version 20. Findings of the study include that ergonomic work design variables have a significant impact on employee stress reduction. The study, however, recommends that; to enhance employees well being, organizations need to balance work demands, employees' skills, and the nature of the equipment used in completing a task. The study concludes that ergonomics has an enormous impact on the performance of employees in Globacom and MTN organizations.
... Ergonomic chairs can influence an individual's work performance by avoiding fatigue and tension [17], [18]. Adjustable chairs with strategically positioned armrests can minimize the load on shoulder and arm muscles [31]. It can also minimize the tension in the neck area. ...
The lack of comfort due to workplace environment impact could trim down job performance and organizational productivity. Literature reviews indicate that ergonomic workplace environment that is strongly associated with the job performance. Employees' perceptions to be examined by the organizations to ensure the excellent job performance. Thus, 295 officers were selected using proportionate stratified random sampling with two-section questionnaire. The data were analyzed using statistical package for the social sciences (SPSS) and analysis of a moment structure (AMOS) software. The research findings show that acoustic is the most crucial factor (0.928) followed by lighting (0.898), workstation design (0.846), working hours (0.670), and chair (0.563). Ventilation is still significant to the whole environment although scored the lowest coefficient value (0.385). These findings provide valuable information to organizations in their attempts to sustain the human resources so that they are always competitive and productive in facing the challenges of the environmental change.
... A study from Wojcikiewicz (2003) determined the three functions of chairs used by an employee to increase employees' effectiveness, minimize fatigue and stress while performing their tasks, and fit the body posture. Cook, Burgess and Papalia (2004) believed that strains at neck, shoulder, and arm muscles can be reduced if the employees use chairs with armrests and have adjustable function. It was suggested by Davis et al. (2020) that there are four key components of the best chairs to be used by an employee: adjustable height, adjustable armrests, five casters, and lumbar support in the back of the chair. ...
... Some studies have suggested that arm support can decrease neck and shoulder muscle activity during keyboard use among computer users, which is consistent with the results from mobile phone use (Cook et al., 2004;Marcus et al., 2002). There is a difference that arm support cannot reduce muscle fatigue of the hands while playing mobile games. ...
Background
The popularity of mobile gaming among adults has raised concerns about the adverse health effects of localized muscle and eye fatigue. This study aimed to investigate how arm support and mobile game control characteristics affect muscle and eye fatigue, and postural changes.
Methods
Twelve subjects, ages 21–24 years old, were recruited to play a mobile game for 60 min. Participants used two postures (sitting with and without arm support) and two game control modes (touch and rocker). Electromyography measured the abductor pollicis brevis, the upper trapezius, and the extensor carpi radialis muscles. A motion capture system was employed to assess postural changes. Self‐reported fatigue was measured using Borg's scale and Heuer's questionnaire.
Results
Arm support had a significant effect on muscle fatigue and posture, including a lower rating of perceived exertion in the shoulder (p < .05) and arm (p < .01), an increase in neck and trunk forward flexion between 22% and 34%, an increase in forearm bearing angle of 97.63%, and a decrease in upper arm bearing angle of 25.94% in the group without arm support. Blink for touch mode was 10.57% higher than for rocker mode.
Conclusion
Arm support was effective in reducing fatigue in the arm and shoulder, but not in the hand. Compared to rocker mode, touch mode increased the visual burden and accelerated visual fatigue. This study provides an understanding of the association between playing mobile games and fatigue, which can help prevent muscle and visual fatigue in mobile gaming.
... Research has evaluated workplace injury risk related to forearm and wrist rest use in jobs requiring extensive keyboard and mouse use. 15,16 These studies focused on muscle activation and kinematics of the neck, back, and upper extremity, but the effect of forearm compression on tendon-SSCT shear injury risk has not been investigated. ...
Cumulative shear strain of the subsynovial connective tissue (SSCT) surrounding finger flexor tendons plays a significant role in the development and progression of carpal tunnel syndrome. Biomechanical risk factors can alter tendon‐SSCT shear strain but the effects of external mechanical compression and localized ischemia have yet to be investigated. In a laboratory study with 19 healthy participants, colour Doppler ultrasound imaging was used to quantify relative motion between flexor digitorum superficialis tendon and SSCT during repetitive finger flexion‐extension under various conditions of external mechanical compression (palmar and forearm compression), ischemia and different movement speeds (0.75 & 1.25 Hz). Forearm compression reduced tendon displacement (baseline = 28.5±4.1 mm vs. forearm = 27.0±4.6 mm; p = 0.043) and showed a trend for reduced SSCT displacement while palmar compression had no significant effects on tendon‐SSCT motion. Compared to baseline, partial ischemia decreased SSCT displacement (baseline = 22.9±3.3 mm vs. ischemia = 22.0±3.3 mm; p = 0.015), while tendon displacement remained unchanged. In all experimental conditions, faster movements elicited greater tendon‐SSCT relative motion. Our findings suggest that palmar compression may not negatively impact tendon‐SSCT relative motion, but forearm compression may require further investigation. Localized ischemia in the forearm may alter the gliding conditions within the carpal tunnel and affect tendon‐SSCT relative motion, which bridges an important gap between blood flow in the carpal tunnel and shear injury risk. These findings contribute to the growing body of literature supporting the role that cumulative tendon‐SSCT shear injury may have on the pathomechanics of carpal tunnel syndrome. This article is protected by copyright. All rights reserved.
... Ten university students, consisting of five males and five females, were enrolled in this study. All participants are experienced in working on computer or portable computer for minimum 6 months [16], minimum fifteen hours as the median hours for computer use [17], and had no evidence of Carpal Tunnel Syndrome and musculoskeletal disorders conditions on upper extremity based on physical examination and medical history [14]. ...
Carpal Tunnel Syndrome (CTS) is one of the most common neuropathies which occurs due to repetitive activity of hand using non-neutral wrist posture whether in flexion, extension, or ulnar and radial. Even though this posture may be inevitable, however it should be confined in maximum range. Thus, this is very significant to develop the allowable of maximum deviation of wrist. Objective of this study is to determine the maximum range of wrist postures in such four motions with evaluating the muscle contraction at wrist. A case study applied is to type a manuscript using computer. Experimental study was conducted by using electromyograph to identify Maximum Voluntary Contraction (MVC) on Flexor Digitorum Superficialis (FDS) and Abductor Pollicis Brevis (APB). Ten healthy university students (5 females, 5 males) were participated with age between 20 to 23 years old. The statistical analysis was conducted to test the hypothesis. Result of this study shows that the suggested maximum wrist posture range is not greater than 30˚ extension, 20˚ flexion, 20˚ ulnar, and 20˚ radial, although the neutral posture of 0˚ was highly suggested. This guideline is proven to be valid for both male and female.
... There has been growing evidence that WRMDs among computer office workers are mainly due to the occupational hazards/ risks presence in the working environment which may impose a biomechanical load among workers, known as physical risk factors [8,10]. The excessive exposure of physical risk factors to the workers may increase the muscular load and muscle activity which eventually may lead to the development of musculoskeletal disorders in different body regions among computer users [11,12]. An awkward posture, prolonged sitting duration, prolonged duration of computer use, and improper design of computer pointing devices such as the mouse and keyboards were the most known risk factors associated with the occurrence of WRMDs among computer users [4,8,13,14]. ...
In conjunction with the Industry 4.0, the computer usage among office workers had increased tremendously in past recent years. The recent technology development with a different type of pointing devices had exposed the computer office workers with a different type of physical risk factors associated with work related musculoskeletal disorders (WRMDs). Although a different type of observational tools were existed to identify the physical risk factors among computer office workers, however the prevalence rate of WRMDs among computer office workers are still increasing. Hence, the aim of the current study was to provide an overview of physical risk factors that were associated with the development of WRMDs among computer office workers. In addition, the paper also discussed on the preexisting paper and pen observational tools that were used previously to identify the risk factors of WRMDs among computer office workers. In conclusion, physical risk factors of WRMDs among computer office workers were consists of task, environmental and technology/equipment factors. None of the paper and pen ergonomic observational tools cover the entire physical risk factor that causes the WRMDs among computer office workers. In addition, the majority of the tools were not validated. Hence, the information from the current study can help the respective agencies to develop a new and validated ergonomic paper and pen observational tool that covers the entire physical risk factors (task, environmental and technology/equipment factors) that associated with the development of WRMDs among computer office workers.
... Arm rest supporting the arms during keyboard and mouse use is a preferable working posture for most computer users [25,26,27]. Suitably designed armrests can reduce muscle loads on the arm, shoulders and neck [28], reduce pressure on the spine and support taskrelated movements [29]. ...
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.
... In order to prevent musculoskeletal symptoms ergonomic recommendations are proposed, among them to support the forearm and to maintain the shoulders in a neutral posture [15][16][17][18][19][20] . Several studies evaluated muscle activity in forearm and wrist support during typing and mouse tasks. ...
[Purpose] To assess the effects of forearm support and shoulder posture on upper trapezius and anterior deltoid activity. [Subjects and Methods] Twenty-three female university students were evaluated. Muscle activity was assessed by a portable surface electromyography (sEMG) system (Myomonitor IV, Delsys, USA). Upper trapezius and anterior deltoid activity were recorded in five shoulder flexion postures: 0°, 15°, 30°, 45° and 60° and in two conditions: with the forearm supported and unsupported. Descriptive data analysis was performed and statistical analysis was conducted by a multivariate analysis of variance with three repeated factors (posture, support and side). [Results] Three-way interactions were not significant. Two-way interaction was significant for support and posture for both muscles, indicating that the muscular activity depends on the forearm support and shoulder posture. The forearm support reduced upper trapezius and anterior deltoid activity for all shoulder flexion angles. The mean and standard deviation for this decrease was 7.8 (SD=4.6)% of the maximal voluntary contraction for anterior deltoid and 3.8 (SD=2.0)% of the maximal voluntary contraction for upper trapezius. In the unsupported condition, increasing the shoulder flexion angle caused an increase in the upper trapezius and anterior deltoid activation. [Conclusion] These results highlight the importance of using forearm support and to maintain neutral shoulder posture, when the upper arms are not supported, to reduce muscle activation. Thus, this study provides evidence about the effect of these recommendations to reduce muscular activity.
... Despite debates on the causality, studies have shown that there may be an association between computer work and musculoskeletal disorders (MSDs) in the upper extremities [1][2][3][4]. Although the injury pathologies are not fully understood, these MSDs are assumed during computer use [13,16,[20][21][22][23]. These studies provide evidence that arm/wrist support may lower muscle activity on the neck and shoulder muscles and promote more neutral wrist postures. ...
Background:
Contact pressure is a risk factor which can contribute to musculoskeletal disorders.
Objective:
The objective of the present study was to determine whether a work surface with a soft, pliable front edge could reduce contact pressure, muscle activity, and subjective musculoskeletal comfort, and improve wrist posture relative to a conventional, hard work surface.
Methods:
In a repeated-measures blinded experiment with eighteen subjects (8 females and 10 males), contact pressure, wrist posture, typing productivity, perceived fatigue, wrist and shoulder muscle activity,and subjective comfort were compared between the two different work surfaces during keyboard use, mouse use and mixed mouse and keyboard use.
Results:
The results showed that across the three modes of computer work,the contact pressure was lower on the soft-edge work surface compared to the conventional work surface (p's <0.03) and subjects reported to have less perceived fatigue in the forearms and wrists. No differences in muscle activity, wrist posture, and subjective comfort were measured between the two work surfaces.
Conclusions:
Given the significant reduction in contact pressure and corresponding lower ratings in perceived fatigue, the soft-edge work surface subjectively and objectively improved measures of contact stress which may reduce physical exposures associated with the onset and development of musculoskeletal disorders.
... However, Green (2012) pointed out this traditional floating posture is not based on any sound research evidence. Over the past decade, there is increasing evidence that supporting the arms during keyboard and mouse use is a preferable working posture for most computer users (Aaras et al., 2001;Cook and Burgess-Limerick, 2001, 2002, 2004a, 2004b. Generally, properly designed armrests can reduce muscle loads on the neck, shoulders and arms (Feng et al., 1997;Weber at el., 1984), reduce pressure on the spine (Aaras et al., 1995;Andersson and Ortengren, 1974), assist in entering or leaving the chair (Alexander et al., 1991), and support task-related movements (Lueder and Allie, 2004). ...
This paper presents an overview of global ergonomics standards and guidelines for design of computer workstations, with particular focus on their inconsistency and associated health risk impact. Overall, considerable disagreements were found in the design specifications of computer workstations globally, particularly in relation to the results from previous ergonomics research and the outcomes from current ergonomics standards and guidelines. To cope with the rapid advancement in computer technology, this article provides justifications and suggestions for modifications in the current ergonomics standards and guidelines for the design of computer workstations. PRACTITIONER SUMMARY A research gap exists in ergonomics standards and guidelines for computer workstations. We explore the validity and generalizability of ergonomics recommendations by comparing previous ergonomics research through to recommendations and outcomes from current ergonomics standards and guidelines.
... Today, the computer is one of the most influential products in living and occupational environment, so that 25% of users have interacted with it over than 50% of their work time [1]. Ever since 1984 they have most physical interaction with the computer mouse, among various computer input devices, between one to two third of time during their work [2]. ...
Some criteria for designing an ergonomic mouse for professional computer users via scenario-based design are presented in order to decrease Work-Related Musculoskeletal Disorders (WMSDs) especially in upper limbs. Library research studies performed based on 5W-H approach extremely tend to medical, ergonomics and functional affairs. Since this study was user-centered design (interaction design), practical research studies performed for better comprehension of users needs by making use of questionnaire, interview and observation procedures in three field of design: ergonomics, functional and aesthetics. First, target group divided into three categories by using AHP method: A-users who work professionally with design, graphic and animation softwares; B-users who work professionally or unprofessionally with other softwares; and C-users who work professionally with engineering softwares. Then, 56 questionnaires are presented to this group and also they interviewed and 15 ones observed during interaction with computer mouse. Finally, 23 design criteria achieved and final idea designed based on these criteria. The most important notes that considered in final design are neutral position of wrist, ulnar deviation prevention and preventing from static and powerful grips.
... Numerous studies have shown that arm/wrist support during computer work can reduce musculoskeletal discomfort in the upper extremities by lowering shoulder muscle activity and promoting more neutral postures (Cook, Burgess-Limerick, & Papalia, 2004;Marcus et al., 2002). However, some studies have also shown that the inadequate arm/wrist support may increase contact pressures in the hand and wrist regions, and these elevated contact pressures are recognized risk factors which can be associated with the onset and development of MSDs (Cobb, An, & Cooney, 1995). ...
Contact pressure has been identified as a risk factor for musculoskeletal disorders (MSDs) in various occupational settings. Given that contact pressure over the palmar aspect of the wrists may increase risks for MSDs, the present study was designed to determine whether a work surface with a soft leading edge could reduce contact pressure and subjective musculoskeletal discomfort without affecting task performance during a series of standardized computer work tasks. Using a repeated-measures blinded experimental design with eighteen subjects, during the performance of a series of standardized computer work tasks, contact pressure, computer work performance and perceived fatigue in the upper extremities were evaluated and compared between a conventional hard-edge and soft-edge work surface. The results found that contact pressure and perceived fatigue in the wrists were lower on the soft-edge work surface compared to the conventional hard-edged work surface (p's < 0.03), whereas no differences were found in computer task performance between the two work surfaces. The study findings showed that soft-edge work surface reduced contact pressure in the wrists and the reduction in contact stress may reduce the risks for developing work-related MSDs when working at the computer.
... 부착 위치는 참고선(Bucholz and Wellman, 1997)을 활용하여 telescopic endblock은 손등 위에 fixed endblock은 아랫 팔 위에 올린 후 수술용 양면테이프로 부착하였다. Calibration은 피실험자별로 실시하였으며, 측정을 위해 피실험자는 의자에 앉은 편안한 상태에서 팔꿈치를 90도로 유지하고, 손바닥은 펴서 작업대 표면 위에 올려 놓으며, 손 목 굴곡/신장 및 요측/척측 편차가 0도인 중립적인 자세를 취하였으며, 이를 영점(Greene and Heckman, 1994; Cook et al., 2004 ...
The goal of this study was to compare wrist posture, muscular loads and perceived comfort among wearable wrist rest (WR), general wrist rest(GR), no wrist rest(NR) during keyboard and mouse use. Thirteen subjects performed text editing task in three test conditions: wearable wrist rest(WR), general wrist rest(GR), no wrist rest(NR). During text editing task, the right wrist posture was recorded by an electrogoniometer and the muscle activity in upper trapezius, anterior deltoid, extensor digitorum, extensor carpi ulnaris were recorded by electromyography. After all of the tests, the subjects rated perceived comfort. Working with wearable wrist rest(WR), compared to no wrist rest(NR) and general wrist rest(GR), decreased wrist radial/ulnar deviation and also decreased muscle activity in upper trapezius and anterior deltoid. At the same time, in work with wearable wrist rest(WR), the subjects rated more comfort at 5 of 8 body locations(shoulder, upper arm, wrist, hand, body).
... The ergonomic chair shall be stable and allow the user moves easily and sits in a comfortable position. The ergonomic chair will affect the workers performance through minimization of fatigue and stress (Cook et al., 2004). Therefore it is a crucial decision should be taken by an organization by providing the workers with ergonomic chair. ...
A healthful work environment brings safety to employees’ physical and mental capabilities in performing their daily routine. In order to reach the healthful work environment, providing the healthful facilities must be taking into account. The examples of facilities are chair seating and lighting. A proper chair seating and sufficient lighting play important role in ensuring employees’ welfare are protected as well their work performance goes up. The ignorance of these important healthful work environments will lead to work stress. Office ergonomics can be provided and used in any type of workplaces like permanent office, home office, virtual office, or even mobile office which the employees working at construction sites for temporary. Employees, who are spending time in office, sitting on chair, interacting with computer and switching on lamp from 8:00 a.m. till 5:00 p.m. is suggested to be provided ergonomics facilities like adjustable chair seating and appropriate lighting level.
... however to the left side signifi cant difference was observed (p<0.01) 15 . ...
Objective
We validated the effect of moveable arm support (Armrest®) on wrist posture during three standardized tasks.
Background
The use of the computer mouse has been increasing over the years and it has been identified as one of the occupational activities related to carpal tunnel syndrome (CTS). The main mechanism for CTS is carpal tunnel pressure (CTP) that could be estimated from the wrist posture.
Method
Using an electronic goniometer, we assessed wrist extension/flexion and ulnar-radial flexion in 15 participants (age: 34.8 [8.7] years) and calculated the time the wrist posture was outside the threshold values previously related to CTP. Specifically, we estimated time when wrist posture yielded >25 mmHg of CTP: wrist extension >32.7°; wrist flexion < −48.6°; wrist ulnar flexion >14.5°; and wrist radial flexion < −21.8°.
Results
Average wrist extension/flexion tends to be 13.4° lower (p = 0.063), while radial-ulnar flexion was 13.2° lower (p = 0.025) when Armrest® forearm support was used in comparison to fixed forearm support. Furthermore, the time spent outside the threshold wrist extension was 25.8% (p = 0.018) lower and ulnar flexion was 37.2% (p = 0.017) lower when using Armrest® compared to a fixed forearm support. Results were independent from tasks.
Conclusion
Armrest® diminished the time spent outside the threshold values related to 25 mmHg of CTP indicative of CTS.
Application
A moveable arm support is a simple and effective way to increase occupational health during computer mouse work.
Background:
In developing countries, the recent increase in computer-related work has considerably increased the occupational complaint of pain.
Objective:
To examine the effects of workstation design, posture and ergonomic awareness on the prevalence of pain for a year in the upper part of the body (eyes, hands, arms, shoulders, lower back, and upper back) among IT professionals in India.
Method:
To investigate the association of risk factors with the prevalence of pain in different body parts, a newly designed online questionnaire titled "A Questionnaire based on ergonomics for IT Professionals" was developed. The psychometric properties of this questionnaire were tested. 110 computer office workers were recruited from IT companies from major cities in India.
Results:
The confirmation of reliability and lack of redundancy of items was provided by the calculation of internal consistency (Cronbach's alpha 0.804) and cross-validation. 60% of participants was male. Mean age was 29.73±6.09 years. The prevalence of pain for a year in the upper part of the body was 38.2%. The frequently reported pains were in the neck (22.7%), lower back area (22.7%), and eye strain (21.8%).
Conclusion:
It was identified that long working hours, excessive usage of smartphones, lack of exercise, incorrect workstation adjustments, and incorrect posture were the risk factors for the prevalence of pain.
Purpose: Vertical and slanted mouse-models have been developed to reduce forearm pronation. Discomfort, performance and stresses have been analyzed with these mice in previous studies but not the learning during familiarization phase.
Materials and methods: Eighteen females performed repeated pointing-clicking tasks with a standard mouse used as a reference followed by a slanted mouse and a vertical mouse in a randomized order. The duration of each task was measured. For each participant-mouse combination, changes in duration upon repeating the task were analyzed using a statistical model including a log-linear slope followed by a plateau. We consider that when the plateau is reached, the participant is familiar with the task.
Results: For both the slanted mouse and the vertical mouse, the plateau is reached after about 30 repetitions of the task. The duration of the plateau was similar for these two mouse-models. For the vertical mouse only, the slope increased significantly when used second versus when used first.
Conclusion: Learning speed appeared slower with the vertical mouse than with the slanted mouse. In light of these findings and those of previous studies, decision makers and employees should consider the slanted mouse rather than the vertical mouse.
Office goers have been compelled to or increasingly constrained to remain seated in a chair–desk complex. Assessment of seat dynamics and user-seat compatibility has been examined, using approaches such as anthropometric, biomechanical, electromyographic and stabilometric analysis, comfort rating and materials construction. This chapter describes biomechanics of sitting, analysis of sitting modes and seated features, and aspects of Balans chairs. Further, it elaborates the ergo-design characteristics of an office chair, including different chair tilting mechanisms. Methodological details of the simulated seat–desk system are included for human–seat–desk interface analysis, covering the effects of the slope of the seat pan, backrest angles, height of armrest, upright and slouch sitting, about body force distribution and muscle activation. Several general risk factors, such as seating system, repetitive use of keyboards/mouse, chair–desk with or without adjustable armrests, supported/unsupported forearm and wrist, are all interconnected and compelling components of workplace constraints in computer work. Discussion includes options of good job design, periodic task rotation, rest breaks, stretching exercises in relieving the physical and mental strain of computer operators.
Hemiplegic patients often have reduced typing speed due to finger paralysis. Our motivation is to develop a keyboard that enables their typing speed to increase. For this purpose, we have developed a three-dimensional keyboard that reduces the distance that fingers move while typing. In this paper, our objective was to construct the finger model that combines the motion speed and muscle fatigue for design of keyboard that can be typed with fast motion speed and low muscle fatigue. In experiment, we measured the finger position using a magnetic 3D motion device and EMG when the participant pressed the proposed key. The experiment was carried out in a variety of the finger postures. We qualified the motion speed and muscle fatigue at each joint angle. Then, we weighted and combined two of the objective functions. We found out the Pareto solution and get an effective keyboard design straight. In the future, we verify the typing speed and finger muscle fatigue during typing the three-dimensional keyboard that is designed based on our finger model.
This study aimed to investigate the effect of a lap board that was developed to prevent musculoskeletal disorders caused by the use of a computer mouse. Study participants were 10 college students in their 20s who did not have any musculoskeletal symptoms. We analyzed the difference in upper limb movements, electromyographic activity, task performance, and subjective discomfort between 2 conditions: use of a mouse with the lap board and use of a mouse placed on a desk. Results of behavior analysis showed that there was a significant difference between the 2 conditions in terms of the average angle of shoulder flexion, shoulder internal rotation, and forearm pronation(p
Introduction: Today, computers are widely used in many homes and workplaces. The relationship between computer
use and musculoskeletal disorders in the neck and upper extremities has been well documented. Muscle fatigue in the
shoulder and arm regions is one of the most frequently reported problems in computer users. Supporting the upper
extremities has been suggested as a way to reduce the static load on upper body muscles while using a keyboard. The
purpose of this study was to determine the effect of elbow and forearm support on upper trapezius muscle fatigue while
typing.
Materials and Methods: Eight students of Bu-Ali Sina University (Hamadan, Iran) participated in this quasiexperimental
study. The surface electromyography activity of the upper trapezius muscle of the dominant side was
recorded in three positions, namely without elbow support, elbow support with the table, and elbow support with a pad
while typing. The muscle fatigue index for the three typing positions was calculated based on the median frequency
slope of the raw electromyography signals. Repeated measures analysis of variance (ANOVA) was employed for
statistical analyses.
Results: Median frequency slope decreased significantly in elbow support with the table in comparison with nonsupport
position (p = 0.04). There were no significant differences between elbow support with a pad and other two
positions.
Conclusion: These results suggested elbow support as a mechanism to delay trapezius muscle fatigue and thus increase
task efficiency. More research is required to determine the advantages or disadvantages of using different pads.
Introduction: Today, computers are widely used in many homes and workplaces. The relationship between computer use and musculoskeletal disorders in the neck and upper extremities has been well documented. Muscle fatigue in the shoulder and arm regions is one of the most frequently reported problems in computer users. Supporting the upper extremities has been suggested as a way to reduce the static load on upper body muscles while using a keyboard. The purpose of this study was to determine the effect of elbow and forearm support on upper trapezius muscle fatigue while typing. Materials and Methods: Eight students of Bu-Ali Sina University (Hamadan, Iran) participated in this quasiexperimental study. The surface electromyography activity of the upper trapezius muscle of the dominant side was recorded in three positions, namely without elbow support, elbow support with the table, and elbow support with a pad while typing. The muscle fatigue index for the three typing positions was calculated based on the median frequency slope of the raw electromyography signals. Repeated measures analysis of variance (ANOVA) was employed for statistical analyses. Results: Median frequency slope decreased significantly in elbow support with the table in comparison with nonsupport position (p = 0.04). There were no significant differences between elbow support with a pad and other two
positions. Conclusion: These results suggested elbow support as a mechanism to delay trapezius muscle fatigue and thus increase task efficiency. More research is required to determine the advantages or disadvantages of using different pads.
This paper summarises the results of studies related to working with visual display units (VDUs) and the associated risk factors for the upper limb. First, the analysis pattern and methodology are defined. Then, the data linked to work organization, stress and psychosocial factors are reviewed, along with data related to biomechanical demands and spatial organisation of the workplace (screen consultation, keyboard entry and mouse manipulation). This bibliographic review demonstrates that, when working with VDUs, the demands on the upper limb are numerous and varied. Stress and psychosocial factors can have a great impact on the entire upper limb, particularly at its root in the shoulder and neck area. Among the biomechanical demands, static posture also exerts a strong pressure on the root of the upper limb. Certain joint positions are also particularly demanding on this limb, particularly at the wrist and shoulder. Whatever the joint, the risk of musculoskeletal disorders (MSDs) of the upper limb is greater as the frequency and duration of these demands increases, even if they are often of low intensity. ne concept of duration of exposure would, therefore, appear to be primordial. In addition, the demands are greater with the use of the mouse rather than the keyboard as they combine cognitive load, static posture and sometimes biomechanical exertion. Finally, this review highlights the conflict that exists between wrist and shoulder in the case of keyboard use : a reduction in demands placed on one of these joints increases demands on another. In terms of prevention, it is therefore vital to take the entire upper limb into consideration. More generally, the use of information appearing in this paper in order to support the prevention of musculoskeletal disorders with VDUs must adopt a global approach, taking into account all the factors identified.
The occurrence of work stress is quite rampant in manufacturing organizations which involved blue collar workers. The literature revealed that poor ergonomics workstation environment is among the major contributor to the work stress problems. Thus, this study aims to examine the relationship between ergonomics workstation factors and the work stress outcomes. Five hundred samples of production operators were derived from eleven manufacturing electronics organizations which were registered with Malaysian International Chamber of Commerce and Industry (MICCI) by using proportionate stratified random sampling. Questionnaires were used for the data collections process. The major finding shows that ergonomically designed workstation is an important strategy in minimizing the work stress outcomes in organizations. Through the multiple regression analysis, each ergonomics workstation factor and component collectively have significant relationship with the work stress outcomes. These findings have been supported by the Pearson correlation analysis which show that all ergonomics workstation factors have high significant correlation with the work stress outcomes. The multiple regression analysis shows health, work area design, shiftwork, humidity system and working hours factors have significant relationship with work stress outcomes. Overall, the findings of this research are important to organizations which are in need of healthy and competent human resources in line with the aspiration of a dynamic human capital development.
The purpose of this study was to determine whether there are significant differences in kinematic variables and muscle activities of the thumb between two smartphone holding techniques. Twelve right handed university students(age 25.4?3.9yrs, height 176.2?5.1cm, weight 75.8?11.4kg, hand length 19.2?1.1cm) who have no musculoskeletal disorder were recruited as the subjects and had experience in using a smartphone for more than one year. Maximum joint angle, angular velocity, muscular activities were determined for each trial. For each dependent variable, paired t-test was used to determine whether there were significant differences between one hand (OH) and two hands ([TH], {\rho}
This chapter examines ergonomic interventions for computer users who experience cumulative trauma disorders (CTDs) in the workplace. The complex nature of these disorders demonstrates the need for holistic, comprehensive, and personalized evaluations. Examples of occupational therapy and other interventions for these disorders and their effectiveness are reported. Recommendations for occupational therapy practice and further research are provided.
Typing styles vary among keyboard users; however few studies have investigated the association between typing style and typing speed. The purpose of this paper is to describe the differences in typing speed between typists who rarely assume extreme postures of the wrist, hands, and fingers with typists who often assume extreme postures. The paper also examines the association between other typing behaviors, such as using a wrist support, and typing speed. Forty computer users were videotaped while typing a standardized text. Their typing postures were rated using the Keyboard Personal Computer Style instrument (K-PeCS). One-way ANOVA's were used to compare typing speed between the rating levels of several items on the K-PeCS. Results suggest that those who frequently isolate their 5 th digit are significantly faster than those who always isolate their 5 th digit. Subjects who "float" their wrists, translate their wrist/hands, do not change pronation angles, use moderate to high force, and use more digits appear to type faster than those who do not.
The purpose of this study was to determine how smartphone use posture affects biomechanical variables and muscle activities. Eleven university students(age: 22.2?2.6 yrs, height: 176.6?4.7 cm, weight: 69.5?7.5 kg) who have no musculoskeletal disorder were recruited as the subject according to having experience in using the smartphone for more than one year. Angular velocity, muscle activity, and thumb finger pressure were determined for each trial. For each dependent variable, a one-way analysis of variance (ANOVA) with repeated measures was performed to test if significant difference existed among different three conditions (p
Repetitive movements for computer users can result in complaints caused by extreme hand posture, finger movements, and force when using the computer, which is known as Work Related Upper Extremity Disorder (WRUED). This study is about the construction of electronic instrumentation for monitoring and quantifying these movements and forces, using sensors to register wrist posture and fingertip force with software developed to collect and process the data. Tests evaluated the performance of the instrumentation with seventeen subjects participating in this study. The maximum extension observed for the first test was 41°, however after training the subject decreased this value to 33°. Six subjects had a wrist extension of between 15° and 41° for the first test; five reduced their wrist extension (between 3° and 33°) during the second test (p = 0.08) while one subject increased instead of decreased it. No subject performed fingertip force greater than 0.77N during the first test; this was reduced to 0.57N during the second test (p = 0.04). The average typing frequency in the group decreased from 3.2Hz to 2.5Hz during the second test (p = 0.01). Results confirm that this solution may potentially contribute to hand movement reeducation, thereby reducing the risk of WRUED for computer users.
Increased carpal-tunnel pressure has been implicated in the pathophysiology of carpal tunnel syndrome, but it is not known whether splints that immobilize the wrist in a functional position of extension minimize carpal tunnel pressure. To determine the position of the wrist that results in the lowest carpal-tunnel pressure, twenty control subjects and four patients who had carpal tunnel syndrome were evaluated with use of a new, dynamic method that continuously measures carpal tunnel pressure throughout the range of motion of the wrist. The pressure was measured by means of a pressure transducer connected to a flexible catheter that had been inserted into the carpal canal. The position of the wrist was measured simultaneously with use of a two-axis electrogoniometer. Aided by a computer monitor that displayed a moving line of real-time carpal-tunnel pressure, each subject was instructed to move the wrist throughout the range of motion and to adjust it to the position that corresponded to the lowest carpal-tunnel pressure. For the control subjects, the lowest carpal-tunnel pressure averaged 8 +/- 4 millimeters of mercury (1.07 +/- 0.53 kilopascals), and the average position of the wrist associated with the lowest pressure was 2 +/- 9 degrees of extension and 2 +/- 6 degrees of ulnar deviation.(ABSTRACT TRUNCATED AT 250 WORDS)
This study examines muscle tension and subjective muscle tension awareness while using a computer mouse positioned to the right of a standard computer keyboard and a centrally positioned trackball. Seventeen volunteer subjects experienced in mouse and trackball use were seated at an ergonomically adjusted workstation. Surface electromyography (sEMG) and subjective muscle tension levels were recorded from four muscle groups (left sternocleidomastoid/scalene, right upper trapezius, right posterior deltoid, and right lower trapezius/rhomboids) during 1-min trials with subjects resting with hands in their lap, while using a trackball below the centre of the keyboard, and while using a mouse immediately to the right of a 101-key keyboard. All subjects showed significantly higher mean sEMG activity recorded from the right upper trapezius, right posterior deltoid, and right lower trapezius/rhomboids during mouse use to the right of a standard keyboard (arm abducted) compared to using a trackball positioned centrally, (p < 0.001). sEMG levels remained elevated during the entire trial period of right side mouse use without evidence of microbreaks (< 1 s epochs of low sEMG activity). sEMG activity from the left sternocleidomastoid/scalene muscles showed no significant change from baseline in any condition. Subjective reports of muscle tension did not correlate with sEMG activity. The authors predict that there will be an overall increase in reports of upper extremity musculoskeletal disorders (UEMSD) and computer related disorders (CRD) when people abduct their arms in order to reach a mouse positioned to the side of standard width, or wider keyboards. Discussed are the applications of sEMG for evaluation of computer keyboard and pointing device use, appropriate ergonomic equipment design, and a methodology for improving muscle awareness, strengthening, relaxation, and workstyle practices to promote healthier computing.
The aim of this study was to compare the postural load during VDU work in the following work postures: (1) Supporting and not supporting the forearms on the table top, (2) Sitting and standing positions, and (3) Sightline to the centre of the screen at an angle of 15 degrees and 30 degrees below the horizontal. The muscle load from the upper part of musculus trapezius and from the lumbar part of musculus erector spinae (L3 level) was measured by electromyography (EMG). Postural angles of head, upper arm and back were measured by inclinometers. The load on m. trapezius when using the keyboard was significantly less in sitting with supported forearms compared to sitting and standing without forearm support. Further, the time and number of periods when the trapezius load was below 1% MVC was significantly greater with support versus no support. The load on the right erector spinae lumbalis was also significantly less and the time when the load was below 1% MVC was significantly longer in a sitting work position with support versus standing without support. In addition, when using a mouse supporting the forearms reduced the static trapezius load in sitting. The results from this study document clearly the importance of giving the operator the possibility of supporting the forearms on the table top.
The study has a parallel group design with two intervention groups (T and S) and one control group (C) of VDU operators. Three serial interventions were carried out in the T and S groups, first a new lighting system, then new workplaces and last an optometric examination and corrections if needed. The new lighting gave significantly increased illuminance levels, increased luminances of the room surfaces and better luminance distribution. The two intervention groups reported significant improvement of the lighting conditions, as well as of the visual conditions and significantly reduced visual discomfort and glare. Significant reduction of headache was found in one of the intervention groups. Optometric corrections reduced the visual discomfort in both the intervention groups. When looking at those given new corrections, a significant reduction was found in the T group and a clear tendency was also found in the S group. The C group reported no improvements for any of these health outcomes. The workplace intervention gave the operator the possibility to support the whole forearm and hand on the table top. Before the intervention there were no significant differences between the three groups regarding shoulder pain and static trapezius electromyographic (EMG) load. Two years after the intervention, a significant reduction of shoulder pain was reported in the T and S groups in parallel with a significant reduction in static trapezius load, while no such reduction was found in the C group. At the same time, both static trapezius load and shoulder pain were significantly lower in the T and S groups compared with the C group. Pain in the forearm and hand showed no significant changes in any of the groups during the study period. However, there seem to be a relationship between pain in the forearm and hand and the time the operator used the mouse. The C group reported significantly higher intensity of pain and used the mouse significantly more than the S group.
This study assessed work postures, movements, psychosocial job demands, and shoulder and wrist extensor muscle activity and registered the prevalence of musculoskeletal symptoms of computer-aided design (CAD) operators.
A questionnaire survey was used to study the use of the computer mouse, psychosocial work factors, and musculoskeletal symptoms among 149 CAD operators. A workplace study was performed using observations, electrogoniometers on the wrists, and electromyography to measure exposures and physiological responses during CAD work among a subgroup of the CAD operators.
Musculoskeletal symptoms were far more prevalent for the arm or hand operating the mouse than for the other arm or hand, and women were more affected than men. The symptoms may be related to such risk factors as repetitive movements, static postures (eg, ulnar-deviated and extended wrist on the mouse side), and static muscular activation patterns. The risk factors were present due to continuous mouse use and possibly also due to high demands for mental attentiveness, precision, and information processing.
Exposure during work with a computer mouse may present a risk for developing musculoskeletal symptoms. Improvements should focus on introducing more variation.
This investigation of current epidemiologic and ergonomic research demonstrates consistent relationships between certain computer-related factors and musculoskeletal disorders.
Awkward upper extremity postures and repetitive wrist motions have been identified by some studies as risk factors for upper extremity musculoskeletal disorders during keyboard work. However, accurate body postures and joint motions of typists typing on standardized workstations are not known. A laboratory study was conducted to continuously measure wrist and forearm postures and motions of 25 subjects while they typed for 10-15 min at a standard computer workstation adjusted to the subjects' anthropometry. Electrogoniometers continuously recorded wrist and forearm angles. Joint angular velocities and accelerations were calculated from the postural data. The results indicate that wrist and forearm postures during typing were sustained at non-neutral angles; mean wrist extension angle was 23.4 +/- 10.9 degrees on the left and 19.9 +/- 8.6 degrees on the right. Mean ulnar deviation was 14.7 +/- 10.1 degrees on the left and 18.6 +/- 5.8 degrees on the right. More than 73% of subjects typed with the left or right wrist in greater than 15 degrees extension and more than 20% typed with the left or right wrist in greater than 20 degrees ulnar deviation. Joint angles and motions while typing on an adjusted computer workstation were not predictable based on anthropometry or typing speed and varied widely between subjects. Wrist motions are rapid and are similar in magnitude to wrist motions of industrial workers performing jobs having a high risk for developing cumulative trauma disorders. The magnitude of the dynamic components suggests that wrist joint motions may need to be evaluated as a risk factor for musculoskeletal disorders during typing.
A prospective epidemiological field study covering a 2 years period has earlier been published. The study has a parallel group design with two intervention groups (T and S) and one control group (C) of Visual Display Unit (VDU) operators. The present paper covers the period from 2 to 6 years of the study. After 3.5 years, the C group got the same intervention in terms of new lighting system, new workplaces and at last an optometric examination and corrections if needed. The C group reported a significant reduction in visual discomfort after interventions while the two groups (T and S) continued to report significant reduction of visual discomfort after 6 years. By supporting the forearm on the table top, the C group reported significant reduction of shoulder and neck pain while the T group reported significant reduction in shoulder and back pain after 6 years. Organizational and psychosocial factors at work and outside work did not show any significant changes during the study period.
The present study focuses on an ergonomic evaluation of 4 computer keyboards, based on a quantitative analysis of wrist posture and typing performance and on subjective analyses of operator comfort during typing. The objectives of this study are (1) to quantify differences in the wrist posture and in typing performance when the four different keyboards are used, and (2) to analyze the subjective preferences of the subjects for alternative keyboards compared to the standard flat keyboard.
Posture (optoelectronic 3D motion analysis system), muscular load (EMG), perceived exertion (rating scales), preference and productivity were investigated in 20 healthy VDU-operators (10 male and 10 female) during text editing with two different data input devices, a mouse and a track-ball. Work with the track-ball entailed lower shoulder elevation and less neck/shoulder muscle activity than work with the mouse. Arm support reduced muscle activity in the neck/shoulder region irrespective of input device used. A table height lower than 3cm above elbow height allowed arm and shoulder support without undue shoulder elevation. Work with the track-ball entailed more wrist extension than work with the mouse. Perceived exertion ratings were lower for the shoulder and higher for the hand with track-ball than with mouse operation. Thus, biomechanical demands differ between different input devices. The women elevated and rotated their right shoulder outwards more than the men during work with both input devices. The overall EMG results showed a higher activity among the women than among the men in two of the examined muscles. This may relate to anthropometric differences which also influence biomechanical load moments. Another reason could be the observed differences in working techniques between the men and the women.Relevance to industryThe design of input devices affects levels of muscular load in neck/shoulder and hand/forearm muscles. Joint positions differ depending on the size and design of the input device and the operators' anthropometry. The design of input devices should be adapted to the differences in work tasks and variations of human dimensions in order to avoid injuries and to enhance the effectiveness of VDU work.
This research examines individual differences in the wrist postures adopted during the use of two pointing devices (mouse and trackball).
A multiple case study of twelve participants was employed.
The use of pointing devices may lead to musculoskeletal discomfort and injury as a consequence of prolonged exposure to postures involving wrist extension and ulnar deviation.
Wrist flexion/extension and radial/ulnar deviation was measured while twelve participants completed two standardised tasks involving horizontal and vertical cursor movements respectively.
Exposure to extreme ulnar deviation and wrist extension was observed in the use of computer mouse and trackball. The trackball involved decreased ulnar deviation and increased wrist extension, however considerable individual differences were observed.
Some users may be placed at risk of injury by prolonged exposure to the use of such devices, while others may not. A trackball may reduce the exposure to extreme ulnar deviation, but in some cases, a trackball may increase exposure to extreme wrist extension.
Use of the computer mouse as an input device at visual display units is increasing, yet few studies could be found that directly addressed related musculoskeletal problems. Tasks similar to mousing, such as keyboarding, have been shown to result in static muscle loading of the shoulder, therefore the potential may also exist for increased neck and upper limb disorder with mouse use. The major aim of this pilot study was to compare the dominant shoulder muscle load from upper trapezius and anterior deltoid, gross postures and discomfort during mousing and keyboarding. This was performed in an effort to investigate whether use of the computer mouse is likely to be a risk factor for neck and upper limb disorders and the extent of this risk compared to keyboarding.Eight subjects performed a 10 min computer task with both mouse and keyboard input. Electromyographs of anterior deltoid and upper trapezius muscles, observations of posture and ratings of discomfort were collected. Group differences suggested increased anterior deltoid loads with mouse use and decreased trapezius loads. Also evident was the considerable inter-individual variation in muscle loads. This may help explain the pattern of work-related neck and upper limb disorders.Relevance to industryInvestigation of shoulder muscle loading during mousing may help identify risk factors contributing to the development of potentially associated neck and upper limb disorders. Costly negative effects of these disorders to industry can include workers compensation claims, decreased productivity and reduced user satisfaction and well being. Once possible risk factors such as shoulder load are identified, approaches to their minimisation in industry may then be addressed.
The aim of this study was to determine whether providing forearm support when using a normal computer workstation would decrease musculoskeletal discomfort in intensive computer users in a call centre. In a randomised controlled study (n=59), thirty participants were given forearm support for 12 weeks and the remainder were given forearm support for the last 6 weeks of the study. Questionnaires were used at 1, 6 and 12 weeks to obtain information about discomfort, workstation setup, working posture and comfort. At 12 weeks, there were fewer reports of neck, back and wrist discomfort amongst all participants. These findings indicate that for the majority of users, forearm support may be preferable to the "floating" posture implicit in current guidelines for computer workstation setup.
Posture (optoelectronic 3D motion analysis system), muscular load (EMG), perceived exertion (rating scales), preference and productivity were investigated in 20 healthy VDU-operators (10 male and 10 female) during text editing with two different data input devices, a mouse and a track-ball. Work with the track-ball entailed lower shoulder elevation and less neck/shoulder muscle activity than work with the mouse. Arm support reduced muscle activity in the neck/shoulder region irrespective of input device used. A table height lower than 3 cm above elbow height allowed arm and shoulder support without undue shoulder elevation. Work with the track-ball entailed more wrist extension than work with the mouse. Perceived exertion ratings were lower for the shoulder and higher for the hand with track-ball than with mouse operation. Thus, biomechanical demands differ between different input devices. The women elevated and rotated their right shoulder outwards more than the men during work with both input devices. The overall EMG results showed a higher activity among the women than among the men in two of the examined muscles. This may relate to anthropometric differences which also influence biomechanical load moments. Another reason could be the observed differences in working techniques between the men and the women.Relevance to industryThe design of input devices affects levels of muscular load in neck/shoulder and hand/forearm muscles. Joint positions differ depending on the size and design of the input device and the operators' anthropometry. The design of input devices should be adapted to the differences in work tasks and variations of human dimensions in order to avoid injuries and to enhance the effectiveness of VDU work.
Computer pointing devices such as the mouse are widely used. Despite this, the relationship between musculoskeletal symptoms and mouse use has not been established. The aim of this cross-sectional study was to determine whether a relationship existed between computer mouse use and musculoskeletal symptoms in a sample of 270 computer mouse users. Factors demonstrating a significant association with symptoms were entered into a step-wise multiple logistic regression, adjusting for age and sex and controlling for potential interdependence between variables. No relationship was found between hours of mouse use per day and reported symptoms. A relationship was found between the variable of arm abduction which is specific to mouse use and symptoms in the neck. Relationships were found between non-mouse-specific risk factors such as stress, screen height and shoulder elevation. The findings of this study support the hypothesis that mouse use may contribute to musculoskeletal injury of the neck and upper extremity. Mouse users are exposed to the same recognised risk factors associated with keyboard use as well as the additional risk factor of arm abduction during mouse use.Relevance to industryComputer keyboard use has been associated with musculoskeletal injuries. Most people now use a pointing device such as the mouse to supplement the computer keyboard. Additional risk factors related to mouse use have the potential to increase prevalence of computer-related injuries.
The aim of the present study was to describe working conditions and the prevalence of musculoskeletal symptoms among male and female VDU operators, and to assess associations between work-related physical and psychosocial exposures and neck and upper limb symptoms by gender. The study population comprised a variety of occupations from both private and public sectors. Data on physical and psychosocial exposures were collected by questionnaires, as were data on musculoskeletal symptoms. Univariate associations between exposures and symptoms affecting the neck and upper limbs were estimated by calculating the prevalence ratios with 95% confidence intervals. We also assessed the potential excess odds ratio attributable to interaction between gender and, one by one, exposure variable. Women (n=785) used the computer on average 3.9 h/day and men (n=498) 3.6. Variation of different work tasks was lower among females than among males. Nineteen per cent of the women and 12% of the men did >3 h of continued computer work without breaks (>10 min) at least twice a week. Twice as many women as men experienced high job strain (high demands and low decision latitude). A higher proportion of women than men reported symptoms ⩾3 days the preceding month from the upper body, irrespective of body region. For many of the studied exposures the prevalence of symptoms in one or several body regions was increased with increasing exposure, indicating exposure-response relationships. Duration of computer work was associated with symptoms among both men and women. Only among men, duration of work with a non-keyboard computer input device was associated with symptoms. Only among women, job strain was associated with symptoms. Time pressure was associated with higher prevalence of symptoms among women. Among men, time pressure was associated with lower prevalence of symptoms. Thus, the associations differed between the genders. Women experienced higher prevalence of symptoms than men in all body regions and they were more often exposed to physical and psychosocial conditions that in previous studies have been considered harmful, than men.Relevance to industryWork-related exposures and the associations between these factors and musculoskeletal symptoms among VDU operators differed in some respect between men and women. This should be considered in intervention programs. The results from this study gives further support to the advice that duration of computer work, time pressure and job strain should be reduced in order to decrease the risk of muskuloskeletal disorders among professional computer workers.
The effects of wrist support on the trapezius and brachial extensor muscle loads during touch-typing were investigated with 12 secretaries, who were suffering pain in one or more of these muscles. They typed for 15 min at each of four experimental situations. The load on the trapezius was significantly greater with wrist support than without, and more marked the higher the support was adjusted. The radial extensor muscle load did not vary significantly. In spite of the higher trapezius load, most of the secretaries preferred a wrist support. Typing performance and body movements, estimated from the movements transferred to a tiltable chair-seat, were both unaffected by wrist support. Whether or not a wrist support should be used for typing cannot be concluded from the present investigation. However, it can be concluded that for touch-typing the keys should be positioned low — probably as low above the thighs as possible.
This paper reviews the current state of the relationship between computer keyboard use and the development of cumulative trauma disorders [CTDs] as found in the literature. Alternative keyboard designs using biomechanical evaluation methods as justification for their use are also reviewed. Critical factors such as the repetitiveness of the keyboarding task, the tendency of users to type with excessive force and forcing users to maintain prolonged awkward and static postures are discussed in relation to CTD development. Suggestions for future research into this area and possible keyboard substitutes are also reviewed.Relevance to industryThe increasing incidence of cumulative trauma disorders (CTDs) in the workplace has led to a search for possible contributing factors and ergonomic interventions. The computer keyboard input device has received much attention in the past and is believed by many to be a prime factor in the etiology of CTD occurrence. This paper reviews the scientific literature published thus far that explores the relationship between CTD development and keyboard use in the service industries.
This document is also available electronically at: http://www.hse.gov.uk/research/rrpdf/rr045.pdf Ten years ago, when the Health and Safety (Display Screen Equipment) Regulations (HSE, 1992) were drafted, the majority of computer interaction occurred with text driven interfaces, using a keyboard. It is not surprising then that the guidance accompanying the DSE Regulations included virtually no mention of the computer mouse or other non-keyboard input devices (NKID). In the intervening period, graphical user interfaces, incorporating ‘windows, icons and pull down menus’ (WIMPS), with a heavy reliance on pointing devices such as the mouse, have transformed user computer interaction. Accompanying this, however, have been increasing anecdotal reports of musculoskeletal health problems affecting NKID users. While the performance aspects of NKID (e.g. accuracy and speed) have been the subject of detailed research, the possible implications for user health have received comparatively little attention. The research presented in this report was commissioned by the Health and Safety Executive to improve understanding of the nature and extent of NKID health problems. This investigation, together with another project examining mobile computing (Heasman et. al., 2000), was intended to contribute to a planned review and updating of the DSE Regulations and accompanying guidance.
1. Musculoskeletal discomfort, work position, and job stress factors were compared in government office workers grouped according to whether they used video display terminals more or less than 4 hours per day. 2. The results of this study suggest that limits on VDT use to less than 4 hours per day do not necessarily protect against health problems. 3. The occupational health nurse's role in preventive measures useful for alleviating the musculoskeletal health problems of office work are discussed.
The aim of the present study was to evaluate the association and impact of occupational exposure and diseases of the shoulder and neck. Prevalence rates, odds ratios, aetiological fractions, and their confidence intervals were computed for pooled and non-pooled data of previous published reports. By comparison with office workers and farmers, dentists had an increased odds ratio for cervical spondylosis (two studies) and for shoulder joint osteoarthrosis. Meat carriers, miners, and "heavy workers" also had significantly higher rates of cervical spondylosis compared with referents. Compared with iron foundry workers, civil servants had a significant odds ratio (4.8) of cervical disc disease and a 0.79 aetiological fraction. Whether this was due to exposure or healthy worker effect was not clear. In four occupational groups with high shoulder-neck load an odds ratio of 4.0 was found for thoracic outlet syndrome with an aetiological fraction of 0.75. Rotator cuff tendinitis in occupational groups with work at shoulder level (two studies) showed an odds ratio of 11 and an aetiological fraction of 0.91. Keyboard operators had an odds ratio of 3.0 for tension neck syndrome (five studies). Unfortunately, owing to the scanty description of the work task, the exposure could be analysed only by job title. Examination of published reports shows clearly that certain job titles are associated with shoulder-neck disorders. High rates and aetiological fractions for rotator cuff tendinitis and tension neck syndrome suggest that preventive measures could be effective. Although job descriptions are brief, the associations noted suggest that highly repetitive shoulder muscle contractions, static contractions, and work at shoulder level are hazardous exposure factors. In reports of cross sectional studies of occupational shoulder-neck disorders presentation of age, exposure, and effect distribution may help for future meta-analysis.
In a field study of 162 VDT and 133 control workplaces it was found that constrained postures of VDT workplaces and in full-time typists were sometimes associated with physical impairments in the hands, arms, shoulders and neck. The reported complaints were confirmed by medical findings on muscles, tendons and joints. The incidence of impairments was increased when the distance from the surface of the keyboards to the desk surface was large; the height of the keyboard from the floor was low; there was insufficient space to rest the forearms and hands; the lateral deviation of the hands operating keyboards was great; and there Was a pronounced inclination or turning of the head. Several recommendations for the proper design of VDT workstations are deduced from the present study
A number of individual, ergonomic, and organizational factors of presumed importance for the occurrence of musculoskeletal disorders were investigated in a group of 260 visual display terminal (VDT) workers. The cross-sectional study utilized medical and workplace investigations as well as questionnaires. The results were subjected to a multivariate analysis in order to find the major factors associated with various upper-body muscular problems. Several such factors were identified for each investigated type of musculoskeletal problem. Some were related to the individual: age, gender, woman with children at home, use of spectacles, smoking, stomach-related stress reactions, and negative affectivity. Organizational variables of importance were opportunities for flexible rest breaks, extreme peer contacts, task flexibility, and overtime. Identified ergonomic variables were static work posture, hand position, use of lower arm support, repeated work movements, and keyboard or VDT vertical position.
Video-motion analysis was used to analyse hand/wrist posture for subjects typing at a 101-key QWERTY keyboard on a 68 cm high worksurface. Three conditions were tested: subjects typed at the keyboard without arm support, subjects typed with adjustable full motion forearm supports, and subjects typed with an adjustable negative slope keyboard support system. The average declination of the negative slope keyboard support chosen by subjects was 12 degrees below horizontal, which flattened the angle of the key tops. Ulnar deviation was comparable in all conditions and averaged 13 degrees for the right hand and 15 degrees for the left hand. Full motion forearm supports did not significantly affect any postural measures. Dorsal wrist extension averaged 13 degrees when typing with or without the full motion forearm supports, but this was reduced to an average -1 degree with the use of the negative slope keyboard support system. Subjects chose to sit at a distance of 79 cm from the computer screen when using the negative slope keyboard system compared with 69 cm without this.
Change in carpal tunnel pressures that result from externally applied forces to the palm of the hand were assessed in five cadaveric specimens. MIKRO-TIP transducers were percutaneously placed into the carpal tunnel at the level of the hook of the hamate. A 1 kg force was applied to the palm of the hand in 16 separate locations. Significant elevations in carpal tunnel pressure were observed for external forces applied over the flexor retinaculum (103 mm Hg) and also for the hypothenar (37 mm Hg) and thenar (75 mm Hg) areas adjacent to the distal aspect of the carpal tunnel. These data demonstrate that the application of external forces on the palm of cadaver hands increases carpal tunnel pressure and the magnitude of the pressure change in the carpal tunnel depends on the location of the applied force.
Work postures and movements of the upper limb were analysed for 12 'mouse' operators and 12 'non-mouse' computer operators employed in word-processing work. Measurements were carried out during correction of a given text. 'Mouse' operators spent 64% of the working time with the operative wrist deviating more than 15 degrees towards the ulnar side, while 'non-mouse' operators spent 96% of the time with the corresponding wrist in neutral position towards radial deviation. The rotation in the shoulder was at all times in neutral position towards inward rotation for 'non-mouse' operators, while 'mouse' operators worked 81% of the time with the shoulder rotated outward more than 30 degrees. 'Mouse' operators corrected a longer text during the given time. Our observations showed long periods of strenuous working postures for 'mouse' operators compared to 'non-mouse' operators. We believe that further investigations need to be carried out on the effects of word-processing techniques and to develop ergonomic work station designs for the 'mouse' and other non-keyboard input devices.
An apparent "outbreak" of cumulative trauma disorders (CTDs) was noted in a subset of white-collar workers employed in medical illustration and medical graphic arts. Among graphic artists (n = 7), there were three cases of carpal tunnel syndrome (CTS), based on patient reports of personal physician diagnoses; no such reports occurred among other workers in the department (n = 39, p = .0023, Fisher's exact test). Jobs were studied to identify possible risk factors for CTDs, and workers underwent a standardized medical screening protocol. Specific work elements were found to be performed more frequently by graphic artists and appeared to be related to increased reporting of distal upper extremity symptoms and electrodiagnostic changes at the wrist. Nevertheless, using a strict case definition of CTS that required electrophysiologic evidence of median mononeuropathy at the wrist and appropriate symptoms or signs, only two persons--one graphic artist and one comparison subject--had evidence of mild CTS. The approach employed in this study of an outbreak of CTDs is an example of a multidisciplinary investigation of CTDs in an office setting.
The objectives of this study were (a) to determine errors in wrist angle measurements from a commercially available biaxial electrogoniometer and (b) to develop a calibration routine in order to correct for these errors. Goniometric measurements were collected simultaneously with true angular data using a fixture that allowed wrist movement in one plane while restricting motion in the orthogonal plane. These data were collected in two sets of trials: flexion/extension with radial/ulnar deviation restricted, and radial/ulnar deviation with flexion/extension restricted. During these trials, we studied discrete 30 degrees increments of forearm rotation. The results showed the expected cross talk and zero drift errors during forearm rotation. The application of mathematical equations that describe the effect of goniometer twist resulted in significant error reduction for most forearm rotations. The calibration technique employs both a slope and a displacement transformation to improve the accuracy of angular data. The calibration technique may be used on data collected in the field if forearm rotation is measured simultaneously with the goniometer data.
The aim of the study was to evaluate four different modes of human-computer interaction. The modes were: use of the keyboard alone as input device, use of keyboard and mouse, use of keyboard and mouse with a three-dimensional arm support, and use of a keyboard with a Trackpoint device in its centre. Ten women and 10 men volunteered to participate. Questions asked were whether working in the different modes influenced shoulder and forearm muscular load differently during word processing, and how much strain on the neck, shoulder and arms subjects perceived in the different modes. Muscular load was studied with electromyography in three shoulder muscles and three forearm muscles. The subjects also rated the different modes in one questionnaire concerning perceived strain and in one concerning preference for any of the modes tested. Intra-individual analysis for each muscle and mode showed two possible ways of decreasing the strain from computer mouse work on the shoulder muscles--either to use Trackpoint or to use the mouse combined with the movable arm support. However, both of these computer-interaction modes increased the muscular load in the hand and forearm.
This case-control study assessed whether office workers who report more severe levels of musculoskeletal symptoms of the upper extremities demonstrate higher levels of keyforce in comparison to controls with less severe symptoms. Office workers reporting working on computer keyboards for four hours per day were classified as cases or controls based upon a median split on a Composite Symptom Severity score (cases = 23, controls = 25). Keyboard force and keying rate were measured during a 15-minute keyboarding task. Measures of task-related discomfort, muscular fatigue, pain, upper extremity symptoms, psychological distress and force were collected at baseline, post-keyboard task, and recovery. Ratings of perceived effort and task credibility were also obtained. Measures of work demands, perceived job stress, and upper extremity strength and flexibility were also collected. The results indicated group equivalence on reported work demands and upper extremity strength. Cases were more likely to receive a medical diagnosis of upper extremity cumulative trauma disorder, awaken from sleep due to symptoms, report higher levels of pain during work, experience greater impact of pain on function, and report higher workload pressure and lower support. Cases generated significantly higher keyboarding forces than controls, although both groups produced forces well above that required to operate the keyboard (4-5 times activation force). Cases reported higher levels of upper extremity symptoms and discomfort than controls, and these measures were highest after the keyboarding task for both groups. No significant correlation between keyforce and key rate was observed in either group. Results suggest that generation of excessive force while working on a computer keyboard may contribute to the severity of upper extremity symptoms. Clinically, the findings suggest that evaluating how an individual worker performs keyboarding tasks, or his or her workstyle, may be helpful in the management of these symptoms and disorders.
This study concerned the influence of 6 positions of the computer mouse on the work table on posture, muscular load, and perceived exertion during text editing.
An optoelectronic 3-dimensional motion analysis system was used to register the postures of 10 men and 10 women using video display units. Muscular load was also registered (with electromyography), as was perceived exertion (with rating scales).
A neutral posture with a relaxed and supported arm showed the least perceived exertion, and the electromyographic results showed low activity in both trapezius muscles in this position. Short operators (all women) showed a numerically higher activity in the 4 examined muscles than the tall operators (all men, except 1). This finding could be related to lower muscle force among women and to anthropometric differences, which also influence biomechanic load moments. Narrow-shouldered operators (8 women and 1 man) and short operators worked with larger outward rotation and abduction of the shoulder in a position of the mouse lateral to the keyboard than the broad-shouldered (7 men and 2 women) and tall operators did. Arm support markedly reduced muscle load in the neck-shoulder region among the operators.
The operators using video display units in this study preferred to use the mouse on a table in a close to relaxed, neutral posture of the arm in combination with arm support. Short and narrow-shouldered operators worked in more strenuous postures of the arm when the mouse was located lateral to the keyboard.
Anecdotal reports of shoulder and arm discomfort related to computer mouse use are common. The aim of this study of ten subjects was to examine the influence of mouse position, relative to the keyboard, on shoulder and arm muscular activity and working posture. Surface electromyography and the Rapid Upper Limb Assessment were used to determine the differences in muscle activity and posture during an editing task in each of three mouse positions. Significantly less anterior (p = 0.01) and middle (p = 0.03) deltoid electromyographic activity was demonstrated when the computer mouse was positioned adjacent to a keyboard without a numeric pad when compared to performance of an identical task with the mouse adjacent to a standard keyboard. Electromyographic activity in trapezius muscle did not differ between mouse positions. Working posture of right handed mouse users is improved by removal of the numeric keypad.
A self-administered questionnaire with questions related to the physical workload at video display units (VDUs) was tested for intra- and intermethod reliability among 36 men and 64 women working with research and documentation. The results showed an acceptable test-retest agreement. The answers to three questions were validated by direct measurements: the locations of keyboard and mouse on the table, and the distance between elbow and keyboard heights when working. The self-reported locations of keyboard and mouse showed good agreement with the direct measurements. A revised version of the questionnaire was used at a telecommunication laboratory to study work postures and musculoskeletal symptoms. Among CAD operators with identical work tasks, the women (n = 67) reported a higher prevalence of musculoskeletal symptoms than did the men (n = 475). Calculated prevalence rate ratios (women/men) for musculoskeletal symptoms ranged from 1.4 (low back) to 3.4 (left elbow). The CAD operators with at least 5.6 hours of mouse use/week (median) reported more symptoms in the arms than did the CAD operators with fewer hours' work. Operators with the mouse located outside an "optimal" area on the table reported more symptoms from shoulder joints (upper arms), shoulders (scapular), elbows, and wrists than did operators with the optimal mouse location. Thus, long hours of work with the mouse, as well as working with the mouse non-optimally located on the table, seemed to be risk factors for upper-limb symptoms.
Surveys have identified a dramatically rising incidence of work-related upper extremity cumulative trauma disorders (UECTDs). Outcome studies have addressed time lost from work and cost of compensation; omitting other significant consequences. We assess health, functional and family outcomes.
We identified 537 Workers' Compensation UECTD claimants. A computer-assisted telephone questionnaire was used to elicit symptom prevalence, functional impairment, depressive symptoms (CES-D scale), employment status.
One to 4 years post-claim, respondents reported persistent symptoms severe enough to interfere with work (53%), home/recreation activities (64%) and sleep (44%). Only 64% of responses to the activities of daily living scale items indicated "normal" function. Job loss was reported by 38% of respondents, and depressive symptoms by 31%.
Work-related UECTDs result in persisting symptoms and difficulty in performing simple activities of daily living, impacting home life even more than work. Job loss, symptoms of depression, and family disruption were common.
The goal of this study was to determine the systematic effect that varying the slope angle of a computer keyboard along with varying keyboard height (relative to elbow height) have on wrist extension angle while typing. Thirty participants typed on a keyboard whose slope was adjusted to +15 degrees, +7.5 degrees, 0 degrees, -7.5 degrees, and -15 degrees. The height of the keyboard was set up such that participants' wrists were at the same height as their elbows, above their elbows, and four cm below their elbows. Results showed that as keyboard slope angle moved downward from +15 degrees to -15 degrees, mean wrist extension decreased approximately 13 degrees (22 degrees at +15 degrees slope to 9 degrees at -15 degrees slope). Keyboard height had a similar effect with mean wrist extension decreasing from 21.8 degrees when the keyboard was lower than elbow height, to 7.3 degrees when the keyboard was higher than elbow height. Potential application of this research includes the downward sloping of computer keyboards, which could possibly be beneficial in the prevention of musculoskeletal disorders affecting the wrist.
The aim was to evaluate (1) the physical workload on neck and upper limb in computer-aided design (CAD) work; (2) the impact of two applications (PROFESSIONAL-CADAM and PRO/Engineering) and (3) two input devices (computer mouse and keyboard), as well as (4) sitting and standing work positions. Fifteen CAD operators were interviewed and examined physically. For nine subjects, the physical workload was measured: electromyography (EMG) of trapezius and forearm extensor muscles, inclinometry of the head, the upper back and upper arms, as well as wrist goniometry. The muscular load was low in CAD work, but the inter-individual variation was considerable. Neither the positions were extreme, nor the movements. The applications, per se, did not have a large impact on the workload, but because of the need for different input devices the effect was strong. Using a keyboard meant higher angular velocities than using a mouse. Hence, when choosing a new software, which requires mainly a mouse as input device, this has to be balanced against the risk of disorders.
Wrist position during pointing device use
- Burgess
- R Limerick
- J Shemmell
- R Scadden
- A Plooy
Burgess-Limerick, R., Shemmell, J., Scadden, R., Plooy, A., 1999. Wrist position during pointing device use. Clinical Biomechanics 14 (4), 280–286
Ergonomics of using a mouse or other non-keyboard device (Research Report No. 045): Health and Safety Executive Officewise: A Guide to Health and Safety in the Office
- V Woods
- S Hastings
- P Buckle
- R Haslam
Woods, V., Hastings, S., Buckle, P., Haslam, R., 2002. Ergonomics of using a mouse or other non-keyboard device (Research Report No. 045): Health and Safety Executive. WorkCover Victoria, 2001. Officewise: A Guide to Health and Safety in the Office. Melbourne. ARTICLE IN PRESS C. Cook et al. / International Journal of Industrial Ergonomics 33 (2004) 463–472
Wrist posture during pointing device use. Paper Presented at the Ergonomics. Enhancing Human Performance Wrist position during pointing device use
- R Plooy
- A Fraser
- K Burgess-Limerick
- R Shemmell
Burgess-Limerick, R., Plooy, A., Fraser, K., 1996. Wrist posture during pointing device use. Paper Presented at the Ergonomics. Enhancing Human Performance. Proceedings of the 32nd Annual Ergonomics Society. Burgess-Limerick, R., Shemmell, J., Scadden, R., Plooy, A., 1999. Wrist position during pointing device use. Clinical Biomechanics 14 (4), 280–286.
Musculoskeletal Disorders and Workplace Factors Goniometer and Tosiometer Operating Manual Practical operation of a biaxial goniometer at the wrist joint
- B Bernard
Bernard, B., 1997. Musculoskeletal Disorders and Workplace Factors. Retrieved 8.9.01, 2001, from http://www.cdc.gov/ niosh/pdfs/97-141.pdf. Biometrics, 1999. Goniometer and Tosiometer Operating Manual. Biometrics, Gwent, UK. Bucholz, B., Wellman, H., 1997. Practical operation of a biaxial goniometer at the wrist joint. Human Factors 39 (1), 119–130.
Work Related Musculos-keletal Disorders (WMSDs): A Reference Book for Preven-tion
- M Hagberg
- B Silverstein
- R Wells
- M Smith
- H W Hendrick
- P Carayon
Hagberg, M., Silverstein, B., Wells, R., Smith, M., Hendrick, H.W., Carayon, P., et al., 1995. Work Related Musculos-keletal Disorders (WMSDs): A Reference Book for Preven-tion. Taylor & Francis, London.
Effect of wrist rest use and keyboard tilt on wrist angle while keying
- T Albin
Albin, T., 1997. Effect of wrist rest use and keyboard tilt on wrist angle while keying. Paper presented at the 13th Triennial Conference of the International Ergonomics Association.
Use of wrist rest by data input VDU operators. Paper presented at the Contemporary Ergo-nomics
- C Parsons
Parsons, C., 1991. Use of wrist rest by data input VDU operators. Paper presented at the Contemporary Ergo-nomics: Proceedings of the Ergonomic Society.
Visual Display Unit Work and Upper Extremity Musculoskeletal Disorders: A Review of Epidemiological Findings Institute for Working Life Wrist and forearm postures and motions during typing
- L Punnett
- U Bergqvist
Punnett, L., Bergqvist, U., 1997. Visual Display Unit Work and Upper Extremity Musculoskeletal Disorders: A Review of Epidemiological Findings. Institute for Working Life, Solna. Serina, E., Tal, R., Rempel, D., 1999. Wrist and forearm postures and motions during typing. Ergonomics 42 (7), 938–951.
Forearm support and computer keyboard use. Paper presented at the ESA 38th Annual Conference of the Ergonomics Society of Australia and the Safety Institute of Australia Forearm support for intensive computer users: a field study
- C Cook
- R Burgess-Limerick
Cook, C., Burgess-Limerick, R., 2001. Forearm support and computer keyboard use. Paper presented at the ESA 38th Annual Conference of the Ergonomics Society of Australia and the Safety Institute of Australia, Sydney, Australia. Cook, C., Burgess-Limerick, R., 2002. Forearm support for intensive computer users: a field study. Paper presented at the HF 2002 Human Factors Conference, Melbourne, Australia.