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Computer mouse use in two different hand positions: Exposure, comfort, exertion and productivity
Abstract
The aim of this study was to determine whether there are differences in exposure, comfort, exertion and productivity between a neutral and a pronated hand position when using a computer mouse. Nineteen experienced VDU workers performed a standardised text editing task with each mouse hand position. The wrist positions and movements in the working arm were registered by an electrogoniometer and the muscle activity in the shoulder, two extensors in the forearm and the first dorsal interossei (FDI) was registered by electromyography. The subjects rated perceived exertion and comfort in work with each mouse hand position. Work with the neutral hand position, compared to the pronated, gave a decreased muscle activity in the extensors of the forearm and in the FDI and a trend indicating a decrease in the frequency of deviation movements in the wrist. At the same time, the subjects showed a decreased productivity and they rated less comfort in work with the neutral hand position.
... The use of computer input devices such as mouse and keyboard only required 7% of the wrist maximum voluntary contraction (Aaras & Ro, 1997). However, the computer input device use forced the operator to maintain non-neutral wrist postures repetitively for a long duration (Gustafsson & Hagberg, 2003;Simoneau, Marklin, & Berman, 2003). ...
... In addition to the non-neutral postures, working using computer input devices also required the wrist perform lowvelocity movements. Jensen et al. (1998) and Gustafsson & Hagberg (2003) found that during the operations of a computer Proceedings of The XXXth Annual Occupational Ergonomics and Safety Conference Pittsburgh, Pennsylvania, USA June 7-8, 2018 ...
... Recent studies show that working using keyboard and mouse whereas made the wrist positioned on non-neutral posture affect the forearm muscle activity. Gustafsson & Hagberg (2003) found that as the consequence of the extension and ulnar deviation angles in the wrist during operation of the conventional mouse, the muscle activity of extensor digitorum and extensor carpi ulnaris were significantly higher than those of vertical mouse. Slightly similar, Van Galen, Liesker, & de Haan (2007) also found that traditional keyboard remarkably increased the muscle activity of extensor digitorum, extensor carpi ulnaris, and extensor carpi radialis compared to the muscle activity on the modified separated vertical keyboard. ...
This study is conducted to examine the effect of wrist postures on the forearm muscle activity while performed low-velocity ulnar deviation movements. Eighteen healthy males participated in this study. The participants were asked to simulate several wrist angles representing the postures of computer input devices operations. The wrist angles were constructed from three levels of wrist extension angles (0 deg, 25 deg, and 50 deg) and three levels of wrist ulnar deviation movement angles (10 deg, 20 deg, and 30 deg). The angular velocity of the ulnar deviation movement was 10 0 /s. In guiding the wrist movement on the desired angles, vertical and horizontal goniometers and metronome were utilized. The muscle activity was recorded using electromyography from two muscles in the forearm region: extensor digitorum and extensor carpi ulnaris. As the results, there was a significant effect of the wrist extension angles on the muscle activity of extensor digitorum as well as static muscle activity of extensor carpi ulnaris. Mean comparison of the muscle activity showed that each extension angles has statistically different level of muscle activity. The lowest muscle activity was found on 0 0 wrist extension angles, while the highest muscle activity was found on 50 0 wrist extension angles. On the other hand, significant differences in the muscle activity due to the effect of ulnar deviation movement angles only occurred for 30 0 ulnar deviation movement angles. The results of this study might be important as a consideration in the design process of computer-input devices.
... The majority of the studies comparing di erent slanted mice focused primarily on the distal part of the limb using the mouse. Their results showed that a slanted or vertical mouse generated reduced nger and carpal muscular activity compared to a standard mouse (Gustafsson and Hagberg 2003;Chen and Leung 2007;Houwink et al. 2009). However, wrist extension was reduced using a standard mouse compared to a slanted or vertical mouse (Houwink et al. 2009;Hedge, Feathers, and Rollings 2010). ...
... This outcome negates Aaras and Ro (1997) suggestion that a vertical mouse is displaced by moving the entire upper limb, whereas the standard mouse is mobilised more by the distal part of the upper limb. As in our study, Aaras and Ro (1997), Gustafsson and Hagberg (2003), Kotani and Horii (2003) and Müller, Tomatis, and Läubli (2010) found no di erence in TRA activity caused by input devices requiring di erent degrees of forearm pronation. ...
... Other studies have reported di erent wrist angles in the abduction/adduction plane: Hedge, Feathers, and Rollings (2010) noted greater wrist adduction using a slanted or standard mouse than a vertical mouse; in contrast, Houwink et al. (2009) observed a mainly abducted wrist position when the trained subjects used a slanted mouse and a mainly adducted wrist position when the trained subjects used a standard mouse, whereas the untrained subjects exhibited no such difference in wrist position. Furthermore, Gustafsson and Hagberg (2003) revealed a more abducted wrist position when using a vertical mouse than when using a standard mouse. ...
This study compared muscular and postural stresses, performance and subject preference in women aged 18-40 years using a standard mouse, a vertical mouse and a slanted mouse in 3 different computer workstation positions. Four tasks were analysed: pointing, pointing-clicking, pointing-clicking-dragging and grasping-pointing the mouse after typing. Flexor digitorum superficialis (FDS) and extensor carpi radialis (ECR) activities were greater using the standard mouse compared to the vertical or slanted mouse. In all cases, the wrist position remained in the comfort zone recommended by standard ISO 11228-3. The vertical mouse was less comfortable and more difficult to use than the other two mice. FDS and ECR activities, shoulder abduction and wrist extension were greater when the mouse was placed next to the keyboard. Performance and subject preference were better with the unrestricted mouse positioning on the desktop. Grasping the mouse after typing was the task that caused the greatest stress. Practitioner summary In women, the slanted mouse and the unrestricted mouse positioning on the desktop provide a good blend of stresses, performance and preference. Unrestricted mouse positioning requires no keyboard, which is rare in practice. Placing the mouse in front of the keyboard, rather than next to it, reduced the physical load.
... Several commercially available mice have been designed with the intent of improving user posture during mousing by making them more vertical. Early efforts focused on providing sculpted, non-symmetrical mice that were designed to improve comfort and wrist posture [1,10]. Some of these mice designs have been shown to provide better posture during mousing [10,11,25]. ...
... Early efforts focused on providing sculpted, non-symmetrical mice that were designed to improve comfort and wrist posture [1,10]. Some of these mice designs have been shown to provide better posture during mousing [10,11,25]. Other studies have shown benefits in reduced muscle load for more vertical mice [11,25,27]. ...
... For example, testing of one vertical mouse demonstrated that the upright pronation-reducing design was successful at reducing subjective pain over a short period of use [1]. Unfortunately, of the 'neutral posture' mice reported in the literature, all have shown reduced pointing performance [1,10,25,26]. Subjective preference measures have also generally been low for these inclinced mice [1,26]. Reduced pointing performance and preference can serve as significant barriers to widespread adoption of a pointing device despite other ergonomic benefits that alternative designs may provide. ...
Background:
Modern computer users use the mouse almost three times as much as the keyboard. As exposure rates are high, improving upper extremity posture while using a computer mouse is desirable due to the fact that posture is one risk factor for injury. Previous studies have found posture benefits associated with using alternative mouse designs, but at the cost of performance and preference.
Objective:
To develop new computer mouse shapes, evaluate them versus benchmarks, and determine whether there are differences in wrist posture, pointing performance, and subjective measures.
Method:
Three concept mice were designed and evaluated relative to two existing benchmark models: a traditional flat mouse, and an alternative upright mouse. Using a repeated measures design, twelve subjects performed a standardized point-and-click task with each mouse. Pointing performance and wrist posture was measured, along with perceived fatigue ratings and subjective preferences pre and post use.
Results:
All of the concept mice were shown to reduce forearm pronation relative to the traditional flat mouse. There were no differences in pointing performance between the traditional flat mouse and the concept mice. In contrast, the fully vertical mouse reduced pronation but had the poorest pointing performance. Perceived fatigue and subjective preferences were consistently better for one concept mouse.
Conclusion:
Increasing mouse height and angling the mouse topcase can improve wrist posture without negatively affecting performance.
... The common GUI input devices used in computer work today are the traditionally designed computer mouse, tablet, and joystick. In recent years, input devices such as the trackball, which are gripped with a less pronated wrist and reduce the muscle load on the upper limb, have been developed (Gustafsson and Hagberg, 2003 ...
... We referenced previous studies (Gustafsson and Hagberg, 2003;Karlqvist et al, 1999), and selected the A target that moves every .75 second and moves 400 times every five minutes. ...
... A study of the performance differences between the computer mouse and other devices found no difference in performance (Karlqvist et al, 1999). But another study reported that the computer mouse was rated higher (Gustafsson and Hagberg, 2003). Consequently, performance studies of different input devices need further consideration about things that can affect the result. ...
This study compared the electromyographic activities and input performance of computer operators using a computer mouse and a trackball. Muscle activities were assessed at the upper trapezius (UT), middle deltoid (MD), extensor digitorum (ED), and first dorsal interosseous muscle (FDI). Twenty-six healthy subjects were recruited, and the test order was selected randomly for each subject. The task set was to click moving targets on a Windows program. The EMG amplitude was normalized using the percentage of reference voluntary contraction for UT and MD and the percentage of maximal voluntary contraction for ED and FDI. To analyze the differences in EMG activity, a paired t-test was used. UT muscle activities were significantly greater when the computer mouse was used (p
... Studie Conlona et al., Fagarasana a Kumara a Schmida et al. poukazují na to, že počítačová myš podporující neutrální postavení předloktí a limitující oporu o měkké tkáně v oblasti dlaně a volární plochy zápěstí může mít ochranný účinek na oblast karpálního tunelu [1,4,12]. Gustafsson a Hagberg ve své práci uvádějí, že neutrální postavení předloktí snižuje aktivitu svalů v oblasti zápěstí (především extenzorů) [7]. Popisují, že předloktí je při úchopu vertikální počítačové myši v relaxované pozici, která odpovídá poloze HK volně visící podél těla při stoji. ...
... Snížená svalová aktivita m. flexor carpi radialis u vertikální počítačové myši může souviset s odlišnou tuhostí tlačítek u sledovaných počítačových myši. V tomto případně je možné konstatovat, že během užívání klasické myši museli probandi vynaložit větší úsilí při kliknutí než u vertikální myši, podobně jako v případě studie Gustafssona a Hagberga [7]. ...
Práce se zabývá popisem postavení předloktí při manipulaci s různými typy počítačových myší během práce u počítače. Cílem studie bylo porovnat aktivitu vybraných svalů horní končetiny pomocí povrchové elektromyografie při práci u počítače vsedě s klasickou a vertikální počítačovou myší.
Do výzkumu bylo zahrnuto 8 probandů (věk 43,1 ± 7,8 let, práce u počítače 8,6 ± 1,4 hodin denně), kteří neměli dřívější zkušenost s vertikální počítačovou myší. Pro hodnocení svalové aktivity vybraných svalů horní končetiny byl využit přístroj pro povrchovou elektromyografii TeleMyo 2400T G2 s programem MyoResearch verze 3 (NORAXON, USA Inc., Scottsdale, Arizona). Měřeny byly tyto svaly (musculi): extenzor carpi radialis longus, flexor carpi radialis, triceps brachii – caput laterale a caput longum, biceps brachii – společné svalové bříško, deltoideus – pars anterior, pars acromialis a pars posterior, trapezius – pars superior, pars medialis,
pars inferior. U všech probandů proběhla dvě měření se stejnými dopředu stanovenými úkony. První měření probíhalo za užití klasické myši. Poté byla probandům předána vertikální počítačová myš HE-Mouse (R-Go Tools B.V., Nizozemí) s instruktáži, jak s ní manipulovat. Po devíti měsících užívání vertikální počítačové myši následovalo druhé měření.
Použitím vertikální počítačové myši došlo k významnému snížení aktivity m. trapezius pars inferior a m. flexor carpi radialis v porovnání s klasickou počítačovou myší. Semipronační postavení předloktí podpořilo centraci ramenního kloubu a relaxaci ruky v porovnání s pronačním nastavením předloktí u klasické počítačové myši. Vertikální počítačová myš se u sledované skupiny probandů jeví jako vhodná volba pro eliminaci muskuloskeletálních potíží v oblasti pletence HK, předloktí a zápěstí.
... Regarding mousepads, the literature is somewhat divided on the benefit of ergonomic mousepads, perhaps because many different types have been used in studies. Noting the evidence of Gustafsson and Hagberg (2003) that forearm muscles loads of inclined mice are lower than those of conventional ones, and the results of a study which revealed that 25° or 30° slanted mice caused lower muscle activity and more neutral working postures for Extensor Carpi Ulnaris, Trapezius and Pronator Teres muscles (Chen and Leung 2007), in this study, we used a slanted mousepad with an adjustable angle. Our previous study indicated that a slanted mousepad caused more neutral forearm and wrist postures and less forearm muscles' activities compared with a non-slanted one (unpublished data). ...
... Despite the attraction of ergonomic mousepads, evidence of their physical benefit is tenuous at best (Schmidt et al. 2015;Trillos-Chacón et al. 2021). In this research we used a slanted mousepad with an adjustable angle, following the physiological evidence that such mousepads relieve some of the strain of mouse work (Chen and Leung 2007;Gustafsson and Hagberg 2003), but we did not find an improvement in ratings of pain. It has recently been asserted that to reduce the risk of wrist MSDs, the most effective strategy involves taking short breaks in work to perform physical exercises to increase blood and lymph circulation, as well as to relax the muscles of the hand (Berezutsky 2018). ...
Objective
To evaluate the effectiveness of an ergonomic intervention program based on the PRECEDE–PROCEED model in terms of improving exposure risks and work-related health problems in emergency medical dispatchers.
Methods
This quasi-experimental study used an interrupted time series design. Participants were 55 employees working in an Emergency Medical Communications Center in Iran. The intervention program was based on the PRECEDE–PROCEED model and included five face-to-face training sessions and installing auxiliary equipment according to best ergonomic principles. Direct observations of the emergency medical dispatchers’ working postures using the Rapid Office Strain Assessment and a survey which included a modified Nordic Questionnaire, Work Ability Score, Visual Fatigue Questionnaire, and a Behavioral Factors Questionnaire were used at three time points: baseline, 1 month post-intervention, and 3 months post-intervention.
Results
The modified Nordic Questionnaire showed significant reductions in pain intensity scores for neck, lower back, knee and ankle after the ergonomic intervention program. In addition, there were considerable post-training improvements in behavioral factors (knowledge and enabling factors) and working postures. No significant changes were observed in Work Ability Scores, or visual symptoms.
Conclusions
An ergonomic intervention program based on a systematic framework such as the PRECEDE–PROCEED model and on-site interventions can be effective in improving and enhancing the working conditions of emergency medical dispatchers. Therefore, it is suggested that ergonomic interventions be implemented based on standard and valid behavioral change models such as PRECEDE–PROCEED model in other work environments in which musculoskeletal pain and digital eye strain are common.
... Recognizing the challenges to control postural methods, they have looked to products for neutral posture solutions. Gustafsson and Hagberg [66] and Kumar and Kumar [88] assessed engineering controls (mouse design) and the risks associated with their use. Both found a neutral posture using alternative devices preferable to the conventional wrist-based mouse operation posture. ...
... A wrist-based method of operating a mouse plants the wrist on a wrist rest or desktop. Gustafsson et al. [66], applying the desktop resting approach, indicated that most mice are designed to be operated with a pronated forearm and wrist-based movements. During wrist-based mouse operation, higher forces were applied to the sides of the mouse and the highest ratings of perceived exertion were in the wrist, hand, and fingers [9,11,50]. ...
BACKGROUND: Musculoskeletal disorders (MSDs) can be prevented by avoiding trauma caused by poor posture, compression, force, and repetition. Neutral postures are recommended to avoid MSDs.
OBJECTIVE: This study introduces Mouse With Your Arm™ (MWYA) methodology which promotes sitting back in a chair, using the chair’s armrest for forearm support at relaxed elbow height, matching surface and armrest height, and keeping the mouse on the surface edge. This position allows optimal task chair use, facilitates movement and neutral postures, avoids compression and contact stress, and is effective in mitigating MSDs.
METHOD: MWYA was applied and measured in the field for more 23 years providing over 3,500 individualized assessments to integrate a participant’s unique characteristics, reported health concerns, tasks, tools, and environment to achieve and sustain whole-body neutral and comfortable working postures.
RESULTS: Previous research has consistently recommended use of forearm support by a desk, apparatus, or wrist rest, and resulted in non-neutral, static postures and measured health consequences. By using armrests for support, MWYA avoids the potential of MSDs as can be caused by these previously endorsed postures.
CONCLUSION: By applying the five MWYA principles, computer users comprehend neutral posture and put forth the effort essential to creating healthy human computer relationships.
... In the wake of Douglas Engelbart's Mother of All Demos, the computer mouse has grown into one of the most engineered input devices [20]. Besides proprietary work, there has been published research on almost every factor imaginable: the shape of the device [17,19,23,25,26,30,34,39,41], its weight [16], the control-to-display (CD) gain function [13,14,50], the resolution of the displacement sensor [6,14,42,44], and many more. Yet it is fascinating to observe that for one factor, the placement of the sensor in the bottom of the device, the proper examination has been overlooked in academic research. ...
... Continuous use of a mouse, especially in dragging, is known to increase carpal tunnel pressure [30] and potentially lead to carpal tunnel syndrome. Slanted or vertical designs, also known as an ergonomic mouse, are known to reduce pronation of the wrist and muscle use but produce adverse effects on pointing performance in general [17,23,39,41]. Some research has shown that a vertical ("ergonomic") shape can indeed be beneficial ergonomically [25], and performance approaches the levels of a regular mouse design with practice [26]. ...
Computer mice have their displacement sensors in various locations (center, front, and rear). However, there has been little research into the effects of sensor position or on engineering approaches to exploit it. This paper first discusses the mechanisms via which sensor position affects mouse movement and reports the results from a study of a pointing task in which the sensor position was systematically varied. Placing the sensor in the center turned out to be the best compromise: improvements over front and rear were in the 11--14% range for throughput and 20--23% for path deviation. However, users varied in their personal optima. Accordingly, variable-sensor-position mice are then presented, with a demonstration that high accuracy can be achieved with two static optical sensors. A virtual sensor model is described that allows software-side repositioning of the sensor. Individual-specific calibration should yield an added 4% improvement in throughput over the default center position.
... Vertical optical mice have been shown to reduce biomechanical loading and musculoskeletal outcomes in the distal upper extremity region and musculoskeletal outcomes in the proximal upper extremity region compared to a conventional mouse. Experimental studies have demonstrated decreased forearm muscle activity, pronation, and ulnar deviation [38][39][40][41]. However, one study reported increased wrist extension [38]. ...
... Conlon et al. also investigated the effects of a vertical optical mouse on musculoskeletal outcomes after one year, reporting a significant effect on right ulnar nerve distal motor latency, and a protective but non-significant effect on incident cases of right upper extremity musculoskeletal disorders and neck/shoulder discomfort [30,43]. However, the vertical optical mouse was also associated with decreased self-reported comfort and productivity [40,41]. ...
Background:
Extended use of conventional computer input devices is associated with negative musculoskeletal outcomes. While many alternative designs have been proposed, it is unclear whether these devices reduce biomechanical loading and musculoskeletal outcomes.
Objective:
To review studies describing and evaluating the biomechanical loading and musculoskeletal outcomes associated with conventional and alternative input devices.
Methods:
Included studies evaluated biomechanical loading and/or musculoskeletal outcomes of users' distal or proximal upper extremity regions associated with the operation of alternative input devices (pointing devices, mice, other devices) that could be used in a desktop personal computing environment during typical office work.
Results:
Some alternative pointing device designs (e.g. rollerbar) were consistently associated with decreased biomechanical loading while other designs had inconsistent results across studies. Most alternative keyboards evaluated in the literature reduce biomechanical loading and musculoskeletal outcomes. Studies of other input devices (e.g. touchscreen and gestural controls) were rare, however, those reported to date indicate that these devices are currently unsuitable as replacements for traditional devices.
Conclusions:
Alternative input devices that reduce biomechanical loading may make better choices for preventing or alleviating musculoskeletal outcomes during computer use, however, it is unclear whether many existing designs are effective.
... (Computer arm syndrome is a musculoskeletal disorder that typically manifests as pain in the upper extremities and the posterior region of the neck). The side of the upper extremity used to operate the mouse [8,[21][22][23][24], differences in mouse positions [25,26], differences in the shape of the mouse [20,[27][28][29], the speed of mouse use in detailed operations [30], and differences caused by the use of armrests [29] can all contribute to CRDs that arise from the use of a mouse. However, these previous investigations of mouse-based activities have primarily focused on the association between operating a computer and musculoskeletal disorders and many of them have examined the relationship between muscular activity and task-induced stress based on electromyography data. ...
... (Computer arm syndrome is a musculoskeletal disorder that typically manifests as pain in the upper extremities and the posterior region of the neck). The side of the upper extremity used to operate the mouse [8,[21][22][23][24], differences in mouse positions [25,26], differences in the shape of the mouse [20,[27][28][29], the speed of mouse use in detailed operations [30], and differences caused by the use of armrests [29] can all contribute to CRDs that arise from the use of a mouse. However, these previous investigations of mouse-based activities have primarily focused on the association between operating a computer and musculoskeletal disorders and many of them have examined the relationship between muscular activity and task-induced stress based on electromyography data. ...
Objectives:
This study investigated the association between task-induced stress and fatigue by examining the cardiovascular responses of subjects using different mouse positions while operating a computer under time constraints.
Material and methods:
The study was participated by 16 young, healthy men and examined the use of optical mouse devices affixed to laptop computers. Two mouse positions were investigated: (1) the distal position (DP), in which the subjects place their forearms on the desk accompanied by the abduction and flexion of their shoulder joints, and (2) the proximal position (PP), in which the subjects place only their wrists on the desk without using an armrest. The subjects continued each task for 16 min. We assessed differences in several characteristics according to mouse position, including expired gas values, autonomic nerve activities (based on cardiorespiratory responses), operating efficiencies (based on word counts), and fatigue levels (based on the visual analog scale - VAS).
Results:
Oxygen consumption (VO(2)), the ratio of inspiration time to respiration time (T(i)/T(total)), respiratory rate (RR), minute ventilation (VE), and the ratio of expiration to inspiration (Te/T(i)) were significantly lower when the participants were performing the task in the DP than those obtained in the PP. Tidal volume (VT), carbon dioxide output rates (VCO(2)/VE), and oxygen extraction fractions (VO(2)/VE) were significantly higher for the DP than they were for the PP. No significant difference in VAS was observed between the positions; however, as the task progressed, autonomic nerve activities were lower and operating efficiencies were significantly higher for the DP than they were for the PP.
Conclusions:
Our results suggest that the DP has fewer effects on cardiorespiratory functions, causes lower levels of sympathetic nerve activity and mental stress, and produces a higher total workload than the PP. This suggests that the DP is preferable to the PP when operating a computer.
... Simple 3° of addition in viewing monitor effect in amplified distress (Kumar, 1994). To prevent the musculoskeletal distraction in the VDT facility, It is suggested to obtain a better position a little incline towards the top point of the monitor (Ewa Gustafsson et al., 2003). Both the whole period of stationary muscle pressure and how many times the muscle pressure drop less than 1% (MVC) maximal voluntary contraction linked at the muscular indication (Veiersted 1993). ...
In Engineering Industries suffering due to industrial wound and ill health, of the Computer Numerical Control machines operators are in the increasing trend, in the subjective analysis which we carried out for the CNC machine, the operators expressing the discomfort at the neck, upper back, lower back, shoulder, and arm because of working with the keys in the controls and viewing the display. The aim of this examination is to identify the most favourable location of control and display through various muscles that activate while performing in CNC machine operations. We introduce surface Electromyogram (EMG) to determine the muscle activity and deliberate on plane of the body close to respective muscles of an operator.The muscle activity measured for all the twenty subjects, at five different levels to find out the best optimal location for controls and display to establish the findings of the subjective study. Though there is no clear trend when all the subjects are aggregated, it is seen that 90 cm-100 cm be the optimum range for the midpoint of the control panel and 143cm-148 cm appears to be the optimum range for the midpoint of the display. Since changes in muscle activity are comparatively small for all the six muscles taken for study, however, the effect of cumulative activity borne over a shift, week, month, and year are to be considered. Muscle activity may increase in repetitive head/finger movements. These combined effects are to be captured for the ergonomic design of the CNC operator interface.
... Hand-intensive tasks such as operation of the trackball can increase the incidence of upper extremity MSDs (Armstrong 1990;Keir, Bach, and Rempel 1999). Furthermore, many studies have identified pointing devices as potential risk factors for MSDs Chang, Choi, et al. 2017;Lin, Young, and Dennerlein 2015;Jung and Jang 2015;Jung 2014;Gustafsson and Hagberg 2003;Liao and Drury 2000;Hagberg and Rempel 1997;Punnett and Bergqvist 1997;Zipp et al. 1983). ...
This study analyzed natural press motions of the index, middle, and ring fingers for ergonomic design of the positions and surface angles of the left, middle, and right trackball buttons. Finger motions of 26 male participants for naturally pressing the trackball buttons were recorded after the participants adjusted the trackball buttons to their preferred locations for comfortable pressing. The natural positions of the finger pulps formed a symmetrically rainbow-shaped reach zone for the fingers. The natural press angles of the fingers’ motion trajectories to the vertical reference line ranged from 14.2° to 20.5°, suggesting an 18-degree surface from the horizontal line for the trackball buttons. Regression formulas (adjusted R² = 0.90 ± 0.07 and mean squared error =8.55 ± 7.52 mm) were established to estimate the natural positions of finger pulps from hand segment lengths and joint angles for a population having different hand sizes from this study.
Relevance to Industry: Trackball buttons designed based on the natural press motions of fingers can provide users with a low physical workload and a high comfort level. This study analyzed the natural press motions of the index, middle, and ring fingers for designing the positions and surface angles of trackball buttons.
... Durch Druckmessung innerhalb des Karpaltunnels konnte nachgewiesen werden, dass bei Arbeit mit dem PC-Eingabegerät "Maus" deutlich höhere Werte gemessen werden als bei Ruhen der Hand auf der Maus und dabei Grenzwerte überschritten werden, die eine Nervenschädigung verursachen können [12]. Auch die höhere Muskelaktivität im EMG bei pronierter Handstellung wurde bereits bestätigt [13], sowie höheres Gewicht des PC-Eingabegerätes "Maus" als Ursache für eine erhöhte Muskelaktivität im Unterarm identifiziert [14]. ...
Zusammenfassung
Fragestellung Wegen epidemiologisch hoher Prävalenz von Schulter- und Nackenschmerzen besteht Anlass zur Ursachenforschung, weshalb wir Muskelaktivitäten bei Nutzung verschiedener PC-Eingabegeräte verglichen.
Material und Methoden Wir maßen bei 34 Probanden die Muskelaktivität des Armes und Schultergürtels mittels Oberflächen-EMG in standardisiertem Arbeitsplatzsetting und erhoben durch Fragebögen die Nutzerakzeptanz.
Ergebnisse Bei Nutzung einer weit verbreiteten Standard-Maus zeigte sich in allen gemessenen Muskeln statistisch signifikant gegenüber ergonomischeren Eingabegeräten die höchste Aktivität. Die Auswertung der Fragebögen ergab stark variierende Bewertungen: geringere Aktivierung der Muskulatur korrelierte nicht mit subjektivem Komfort.
Diskussion und Schlussfolgerung Zur Reduktion von Muskelbeanspruchungen im Schulter-/Nackenbereich kann der Wechsel auf ein ergonomischeres Eingabegerät hilfreich sein. Je nach Beschwerdebild kann das passende Gerät nach unseren Daten ausgewählt werden. Zu berücksichtigen ist die zu erwartende Akzeptanz der Nutzer.
... Prior studies on the effect of different types of information and communication technology input devices have demonstrated that design differences can have significant impacts on posture, muscle activity and discomfort in neck and upper extremities (Briggs et al., 2004;Chany et al., 2007;Gustafsson and Hagberg, 2003;Oude Hengel et al., 2008;Rempel et al., 2007;Straker et al., 2008b;Xiong and Muraki, 2014). However, there is very limited knowledge about differences in thumb postures, muscle activity, and discomfort during the use of these two basic types of phones. ...
This study aimed to compare thumb kinematics and upper limb muscle activity, and the influence of hand size, when texting on a keypad smartphone and a touchscreen smartphone. Furthermore, the study compared exer-tion, discomfort, and performance when texting on the two phones. The thumb kinematics were tracked using a 3D motion analysis system and muscle activity was registered in six upper limb muscles using surface electro-myography in 19 participants. When texting on the touchscreen phone compared to the keypad phone thumb flexion (p = 0.008) and flexion/extension range of motion were smaller (p = 0.02), the thumb was on average less internally rotated (p = 0.02), and activity (50th and 90th percentile) of the thumb and forearm muscles was lower (p ≤ 0.05). The differences in thumb flexion were found only in the group with shorter hands and the differences in muscle activity was found only in the group with longer hands. These findings suggest there are differences in risks for developing musculoskeletal disorders during smartphone use with different key activation mechanisms and different hand sizes.
... Woods et al. (2003) proposed identifying factors of a good design in relation to operations, performance and comfort of non-keyboard input devices (NKID). Gustafsson and Hagberg (2003) proposed that the positions of the forearms and hands influence the exposure, comfort, exertion, and productivity of the operational equipment. Jindrich et al. (2004) measured finger joint kinematics during voluntary finger tapping on a keyboard keyswitch using miniature electro-goniometers and high-speed photography. ...
A method was proposed in this study for assessing the interface operating efficiency of a remote control. The operating efficiency of a product interface can be determined by the proposed approach in which the related dimensions of human palms were measured. The reachable range (blue zone) and the most comfortable range (green zone) were investigated when a user used a single hand (right hand) to operate the remote controls. After that, new remote control designs were created based on the measurement results and the operating efficiency of commercially available remote controls were determined for comparison. The operating efficiency is determined by calculating the overall distance of finger movements when manipulating the buttons and the overall operation time was recorded. The subjects who joined the body measurements and performed the experiments are right-hander Asian college students between the ages of 22 and 28. After further optimization, the reachable range became more average during one-handed operations and those frequently used keys were included into the comfortable range. The resulting operating efficiency performance is higher than commercially available products. The results serve as a good reference for detailed modifications of the products or for the decision making of design proposals.
... 이렇게 컴퓨터는 지난 수십 년간 필수불가결한 존재가 되었다 (Peter J. Keir et al. 1999) [1] . 컴퓨터는 [2] . 현재 마우스 시장의 규모는 약 2 조원대로, 연간 8~10%씩 꾸준히 증가하고 있다. ...
... The effects of using a conventional computer mouse on forearm and wrist symptoms have been studied [22]. According to Zipp et al. [23], Hagberg [24] and Liao and Drury [25], pronation of the forearm may result in the development of upper-extremity MSDs, and the extension of the wrist increases carpal tunnel pressure (CTP) [26][27][28][29]. ...
Recently, computer, mobile phone, and Internet use has increased. This study aimed to determine the possible relation between self-reported wrist and finger symptoms (aches, pain, or numbness) and using computers/mobile phones, and analyze how the symptoms are specifically associated with utilizing desktop computers, portable computers or mini-computers, and mobile phones. A questionnaire was sent to 15,000 working-age Finns (between the ages of 18–65). Via a questionnaire, 723 persons reported wrist and finger symptoms often or more. Over 80% use mobile phones daily and less than 30% use desktop computers or the Internet daily at leisure. For example, over 89.8% had quite often or often experienced pain, numbness, or aches in the neck, and 61.3% had aches in hips and the lower back. Only 33.7% connected their symptoms to computer use. In the future, the development of new devices and Internet services should incorporate the ergonomics of the hands and wrists.
... This methodological implication is logical as fatigue/tiredness is hard to be explained objectively (Meeuwesen et al., 2002) and there is no universal instrument or clinical assessment to diagnose fatigue. Fatigue could only be described by tangible physical symptoms such as musculoskeletal injuries (Gustafsson and Hagberg, 2003). The factor analysis result also suggests that the original four stress outcomes to be reduced into three. ...
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.
... 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.
... 과제는 text editing을 활용하였다 (Karqvist et al., 1994;Gustafsson and Hagberg, 2003 (Zipp, 1982). 전방 삼각근(AD), 지신근 (ED)와 척추수근신근(ECU)는 기존의 연구를 참고하여 부 착을 하였다 (Basmajian and De Luca, 1985;Basmajian and Blusmenstein, 1983;Perotto, 1994 (Keir et al., 1998;Rempel et al., 1994;Rempel and Gordon, 1998 ...
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).
Abstract
This study simultaneously compared four working postures (sitting on an office chair, on a ball, standing and pedalling on an ergocycle) and five pointing device configurations (traditional and slanted mouse placed next to and in front of the keyboard, and central pointing device) in relation to sedentary behaviour and musculoskeletal disorders. Pedalling on an ergocycle was the only posture that exceeded the sedentary behaviour threshold of 1.5 METs. This posture resulted in the highest task completion time and was least favoured by participants. Regardless of the pointing device configuration, there was a risk of fatigue in the extensor carpi muscle of the dominant limb. Nevertheless, the central pointing device reduced stress on this muscle compared to mice. Task performance was the best with the traditional mouse. Using the central pointing device while pedalling on an ergocycle led to the lowest task performance and the highest stress on the trapezius muscle.
PRACTITIONER SUMMARY
Compared to standing and sitting on a chair or a ball, using an ergocycle was the only posture reaching a sufficient energy expenditure with respect to sedentary behaviour. Traditional and slanted mice and central pointing device entail a risk of muscular fatigue. However, it was less with central pointing device.
Multiple literatures show evidences of how office workstation set-ups can influence muscle activities. However, the relationship between the postural adoption due to workstation setup and its effect to muscle oxygen saturation among office workers is unclear. The aim of this study was to investigate trends of muscle oxygen saturation and perceived fatigue ratings between different upper limbs posture variations among representative computer users. A repeated measure experiment was conducted on 15 participants to compare the muscle oxygen saturation and perceived fatigue ratings between four different office work posture variations. Parametric and non-parametric statistical analyses were conducted to analyze significant differences on the dependent parameters. Data analysis showed statistically significant trends (p≤0.050) of lower muscle oxygen saturation in workstation set-ups in which participants were adopting raised shoulder and extended arm positions. In addition, the findings revealed that the perceived fatigue ratings on the shoulder, upper arm and lower arm are the lowest (p≤0.050) in workstation condition where subject can adopt neutral postures. The results highlight the effect of good office workstation setup and work postures to individual muscle oxygen saturation and fatigue levels.
The main objective is to conduct review to find wrist related disorders in aged population and suggest neutral hand position computer mouse. Systematic Literature Review (SLR) is carried out that suggests that comparatively less literature is available for elderly mouse users. The results from other researchers show that two most unnatural wrist positions of Ulnar Deviation and Extension are the main cause of hand tiredness and tingling during mouse operation. Observations of other researchers for ergonomic mouse have been presented. It is also concluded that traditional mouse did little to prevent the bending or extension of the hand.
Background:
Numerous people use computer mice for long hours, especially in offices. Mouse users reported various pains and discomfort.
Objective:
The study aimed to assess three types of most common mice (vertical, traditional, flat) in Iran in terms of their effects on carpal tunnel syndrome, hand discomfort, and usability.
Methods:
The Boston carpal tunnel syndrome questionnaire, the Cornell hand discomfort questionnaire System Usability Scale, and Workplace Ergonomic Risk Assessment (WERA) scores were used to assess system usability among vertical, traditional, and flat mouse users. In addition, the participant's hand position was analyzed by observation method.
Results:
Most participants had medium carpal tunnel syndrome severity; however, flat mouse users had a higher score, and the difference between mice was insignificant (p > 0.05). Most mouse users felt discomfort in their small and ring fingers, and the type of mouse significantly affected thumb discomfort level. More flat users felt Pain in the different parts of their hands. The flat mouse has the least SUS score. There was a significant difference between the three mice regarding SUS scores (p < 0.05(. WERA mean values were acceptable for numerous mice. Adopting neutral wrist postures was more common among vertical, flat, and traditional mouse users, respectively; however, the flat mouse users tended to bend their fingers.
Conclusion:
Although wrist postures did not score highly, future studies should assess finger positions. Therefore, vertical mice are preferable to decrease hand disorders.
Introduction
The high prevalence of musculoskeletal disorders in pathologists, together with the current trend towards the digitization of pathology, prompted us to study the different types of input devices employed during the revision of whole slide images, in order to investigate the pattern and extent of muscle activity involved in their use.
Material and methods
A comparative study was made of 10 input devices (conventional and vertical mouse, three trackballs, the Ergopointer™, the Rollermouse™, an optical pen mouse, a touchpad, and the Leap Motion™). Six medical students performed a standardized circuit using a Fitts’ Law based tissue array, digitized. The electrical activity of seven upper limb muscles (adductor pollicis, extensor pollicis longus, extensor digitorum, flexor digitorum, middle deltoid, upper trapezius, and middle trapezius) was measured using surface electromyography.
Results
Statistically significant differences in the overall electrical activity among the different input devices, both absolute values in mV as well as normalized values to the upper limb at rest, were observed (p < 0.001); the Rollermouse™ (0.1027 mV; 139%), Logitech M570 trackball (0.1053 mV; 145%), Ergopointer™ (0.1151 mV; 167%), conventional mouse (0.1251 mV; 191%), and vertical mouse (0.1312 mV; 205%) required less activity, while the optical pen mouse (0.1717 mV; 299%), Leap Motion™ (0.1803 mV; 319%), Expert Mouse trackball (0.1845 mV; 329%), EIGIIS trackball (0.2442 mV; 468%) and the touchpad (0.2560 mV; 496%) required greater muscle mobilization.
Conclusion
We designed a system based on Fitts’ Law to compare input devices in digital pathology.
Variability between compared devices and muscle activity was found. Long-term use could result in different muscular fatigue patterns.
Even though the selection of an input device is a matter of personal preference, its impact on ergonomics should be considered.
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.
Bu araştırmanın amacı; Karadeniz Teknik Üniversitesi (KTÜ) akademik personeline tahsis edilen çalışma ortamının, ergonomiklik açısından mevcut durumunu ortaya koymak ve söz konusu personelin ergonomik çalışma ortamı ve verimlilik konusundaki tutumlarını değerlendirmektir. Analizler sonucunda fakültelerin ergonomiklik düzeylerinin farklı olduğu ve katılımcıların cinsiyet, yaş, unvan ve mesleki deneyimleri açısından verimlilik tutumları arasında istatistiksel olarak anlamlı farklılıkların bulunduğu tespit edilmiştir. Ayrıca işe bağlı olduğunu düşündükleri kas-iskelet ve/veya göz hastalığı olup olmama durumu ile verimlilik tutumları arasında istatistiksel olarak anlamlı bir ilişki bulunmuştur
Under existing network security technology, it is still possible for hackers to impersonate legitimate users and invade a system for malicious destruction. Therefore, this study constructs a user's unique mouse behavior pattern to identify a trusted interaction behavior in a real environment and quantify the effects of different emotions on mouse behavior and the accuracy of the user's trusted interaction behavior identification. First, mouse data was collected for 8 user's trusted interactions on an academic study website (AML). These data were used to construct the basic trusted interaction model by a big data analysis method called a random forest. Second, in a repeated measurement experiment, 18 participants completed tasks on the AML under different emotions, and the emotions' impact on the mouse behavior and accuracy of the user's trusted interaction identification was analyzed. In the results, the accuracy of the trusted interaction behavior identification based on mouse behavior reached 91.82%, and the error rate was lower than 8.18%. Significant differences were observed in horizontal velocity, velocity, and traveled distance under different emotions. However, there was no significant difference in the accuracy of a user's trusted interaction behavior identification under different emotions. Based on these results, the trusted interaction behavior of web users can be accurately identified based on the user's mouse behavior pattern. The user's mouse behavior differs under different emotions, but there is no significant difference on the identification of the user's trusted interaction behavior. The findings help to provide another protection layer for network information security.
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.
Among various types of home appliances, an electric steam iron has a higher risk since it needs to operate under a condition with a higher range of temperature. In this study, a group of college students were invited to operate an electric iron during the experiment in order to investigate the correlation between an operator's hand and the possible contact with the iron soleplate during usage. The purpose of this study was to determine the hand portions which could easily get burned and the portions of the iron soleplate which tend to cause injuries. The results of this study indicated that the hand portions which could easily touch the soleplate are the right-hand side of the thumb and the forefinger. On the other hand, the portions on the soleplate which tend to cause burns are on the left-hand side of the iron, especially the sharper and upper half. The results serve as a good reference for follow-up designers on an iron design based on the safety consideration.
Two pen mouse designs were compared with a conventional mouse design in a laboratory experiment. Sixteen Ss (8 men; 8 women) used each of the mice to perform a series of tasks. Wrist posture was measured while holding each mouse. Results show the pen mice decreased ulnar deviation and wrist pronation, the latter being more reduced for women. However, wrist extension was lowest for the conventional mouse. No significant differences in task performance were found between the 3 designs that were tested. Ss reported that the conventional mouse was easier to use than the pen mice and just over half of the Ss preferred this design. A longer-term study is warranted.
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
Background:
We analyzed muscular activity for different computer mouse positions during the completion of a timed computer task and determined whether the different mouse positions could affect muscular activity, productivity and perceived fatigue.
Methods:
The subjects were nine healthy young men. Two mouse positions were studied: the distal position (DP), with the forearm rested on the desk; the proximal position (PP), with only the wrist rested on the desk. The subjects performed a 16-min task in each position. Surface electromyography data were recorded for the upper back and shoulder muscles. Work productivity and muscular activity were measured for each mouse position. A visual analog scale was used to assess subjective fatigue.
Results:
Muscular activity was higher in muscle (m.) deltoideus (posterior) for the DP, while it was significantly higher in m. inferior infraspinatus for the PP. The visual analog scale score was significantly higher and work productivity was lower in the PP.
Conclusions:
We found that using a mouse in the DP rather than the PP leads to less activity of the external rotators, less perceived fatigue and more productivity. This suggests that the DP is preferable to the PP for computer work involving a mouse.
The aim of this study is to determine the effect of form factors (curvature rate, depth) of mobile devices on hand comfort when using large-screen curved mobile devices. To that end, four muscles (APB, APL, FDI, EDC) were selected and mockups for experiment were developed with four curvature rate levels (flat/100/200/300R) and five depth levels (3/5/7/9/11 mm). User experiment was conducted using three interactions (tapping, dragging, and texting) that usually take place on smartphones. EMG signal of each participant was measured. Combination of curvature and depth could maximize the physical comfort of hands and fingers through the experiment so that the interaction effect between form factors and tasks could be identified. Our results revealed that only APL and FDI had statistically significant muscle activity amounts across the curvature rates. With respect to effect of depth, all four muscles showed statistically significant difference in muscle activity. Moreover, results from the interaction effect among task levels of two tasks (target location of tapping and direction of dragging) and two form factors showed no interaction effect in either tapping or texting. The results of this study could be used to determine the optimal range for form factors of curved screen mobile devices in terms of physical comfort of the hand while using large-screen devices.
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.
To deal with product design method driven by interactive operations, mobile phone was studied as an object product with demands of complex interactions. Interaction process between mobile and human hand was analyzed in detail, and two major interactive operations-holding and key pressing-were observed through experiments, and were statistically studied. Evaluating goals of mobile positioning in palm and comprehensive comfort scale of key pressing were acquired, together with the related variables. Mobile product s design model was established based on coding representations. Problem solving algorithms were designed based on genetic algorithms, which generated optimal rational mobile designs in the solution space through three processes! problem construction, automatic solving and interactive solving in sequence. A prototype system was designed to realize the basic functions of the interactive operation-driven design of mobile. Study proved the feasibility of the driven design method, and showed that design results were influential to interactive operation's expressing method and product coding quality.
The effects of keyboard placement with reference to horizontal and vertical positioning of keyboard were examined (n = 8) on the upper extremity postures and associated EMG activity of arm and back muscles during computer keying tasks. Six experimental conditions were (a) 61 (height of keyboard in cm): downline (outer edge of table), (b) 61: upline (20 cm distance from the outer edge of table), (c) 69: downline, (d) 69: upline, (e) 76: downline, (f) 76: upline. Posture analysis showed that with decrease of work surface height from 76 to 61cm, the elbow extension increased from 89 to 100° (right) and 90 to 110° (left) at upline. Overall, the elbow extension increased with decrease in height for both upline and downline and for all the heights (61, 69 and 76 cm) extension was greater at upline than downline. Electromyographic analysis showed that bilateral upper trapezius activity varied significantly (p<0.001) across the test conditions and observed minimum at 61:downline, whereas, maximum at 76:upline. Further, in all vertical heights (61, 69, 76 cm), upper trapezius activity increased from downline to upline placement.
Hand operation accompanied with any combination of large forces, awkward positions and repetition may lead to upper limb injury or illness and may be exacerbated by vibration. Commercial lawn mowers expose operators to these factors during actuation of hand controls and therefore may be a health concern. A nontraditional lawn mower control system may decrease upper limb illnesses and injuries through more neutral hand and body positioning. This study compared maximum grip strength in twelve different orientations (3 grip spans and 4 positions) and evaluated self-described comfortable handle positions. The results displayed force differences between nontraditional (X) and both vertical (V) and pistol (P) positions (p < 0.0001) and among the different grip spans (p < 0.0001). Based on these results, recommended designs should incorporate a tilt between 45 and 70°, handle rotations between 48 and 78°, and reduced force requirements or decreased grip spans to improve user health and comfort.
Copyright © 2015 Elsevier Ltd and The Ergonomics Society. All rights reserved.
The effect of using five different optical mice on cursor positioning task performance and on wrist posture was investigated. The 5 mouse designs included 1 conventional mouse, 2 angled mice and 2 vertical mice. Results showed that performance was significantly different for the 5 mice for the cursor point-and-click tasks and cursor dragging tasks. Task performance was slowest for the traditional mouse and fastest for the vertical mice. Wrist extension was lowest for the slanted mouse designs and highest for the vertical mice. The results show that performance and posture were affected in opposite ways by these different mouse designs, and that the design features that promote good performance may compromise good wrist posture and vice versa. Overall, an adjustable-size slanted mouse design may offer the best combination of neutral posture and performance. Copyright 2010 by Human Factors and Ergonomics Society, Inc. All rights reserved.
This paper suggested the best work conditions including short break time and the number of mouse clicks on the computer work for the prevention of MSDs on VDT work. Fatigue measures included EMG based parameters. The short break time conditions are grouped into 7, 15, and 30 seconds after every work for 10 min and the number of mouse clicks are divided into 10, 20, and 30 clicks/min. The result of the ANOVA of the shift value of %MVC(Maximum Voluntary Contraction) showed the following: 1) There was a considerable difference as regards to the break time except the number of mouse clicks on the upper trapezius muscle(p<0.05). The best conditions were shown in 15 sec after every 10 min and 30 clicks/min. 2) There were considerable differences as regards to the number of mouse clicks except the break time on the extensor digitorum muscle and extensor carpi ulnaris muscle(p<0.05). The best conditions were shown in 7 sec after every 10min and 10 clicks/min.
In spite of the rapid increase of computer use in our everyday life, not much effort is undertaken to take measures to prevent Musculoskeletal Disorders(MSDs). In this paper, we suggest a movable armrest which would lower the exposure to the MSDs, especially on the vicinity of arm. The aim of this study is to determine whether there are differences in wrist angle variations, forearm muscular loads, comfort and normal performance between the invented movable armrest and a conventional armrest when using a computer mouse. Eight experienced VDU workers performed a standardized simple task set which consists of 15 detailed tasks with each armrest. The wrist angle variations in the right arm were registered by electrogoniometer and the muscle activities in the shoulder, deltoid and two extensors in the forearm were also registered by electromyograph. The subjects rated perceived comfort while performing the tasks with each armrest. Working with the invented armrest, compared to general, gave significantly decreased wrist angle variations at most of the detailed tasks of both biaxial movements. Moreover, as the distance of targets increased, the difference of muscle activities in two different situations trend to be increasing. At the same time, in work with invented armrest, the subjects rated more comfort and they showed decreased normal performances in 8 detailed tasks which were mainly caused by macro moving time.
The objective of this study was to determine whether there are differences in hand muscle activities (APB : abductor pollicis brevis, ED : extensor digitorum, ECU : extensor carpi ulnaris, and EI : extensor indicis) and subjective discomfort according to the three mouse sizes (small, medium, large) and two task types (pointing and scrolling). The mouse size and task type showed significant interaction effects on the total NEMG (p = 0.004) and on the NEMG of the abductor pollicis brevis muscle (p = 0.001). The total NEMG and the NEMG of APB showed the highest value in the 'scrolling' task using the 'small' mouse. However, the NEMG of the EI was different according to the mouse size, and the 'small' mouse showed the lowest value. The subjective discomfort was the lowest in the 'medium' mouse, and all nine subjects preferred the 'medium' size. The hand-size related anthropometric variables showed different correlations according to the task type and mouse size with the NEMGs and subjective discomfort. The results of this study could be used as a basic information for the determination of the proper mouse size according to the hand size.
27 office workers participated in a controlled field trial of a novel computer mouse design. Usability, performance and discomfort measures were taken prior to, during and post a 2 week trial period. Usability was assessed using rating scales based on Davis's Perceived Ease of Use Scale and ISO/DIS 9241-9 draft standard. Performance was measured as time to complete a series of standardised word processing tasks. Body parts discomfort was measured by visual analogue discomfort scales. Workers tended to find the vertical mouse less easy to use, especially in ease of movement. Performance with the vertical mouse tended to be slightly slower. Discomfort tended to be slightly lower for some workers during vertical mouse use.
Studies have shown that wrist goniometers are prone to measurement errors, particularly due to crosstalk. This study compared two wrist goniometer systems: a commonly used biaxial, single transducer (System A) and a biaxial, two-transducer (System B). Wrist angles, range of movement and crosstalk results were compared. With the wrist in 90° of pronation, eight subjects were placed in 20 different wrist postures between −40° and 40° of flexion/extension and between −10° and 20° of deviation.Relative to System B, System A had larger measurement errors and was more prone to crosstalk. There may be two sources of crosstalk: (1) intrinsic crosstalk associated with the design, application and twisting of the goniometer transducer when on the wrist, and (2) extrinsic crosstalk associated with the anatomy and complex movement of the wrist joint. It appears that the majority of the radial/ulnar crosstalk measured with System A was intrinsic crosstalk due to the twisting of the goniometer transducer.
A newly developed mouse, which seemed to give the operator a more neutral forearm position was compared with a traditional mouse. The muscle load was recorded by electromyography from the extensor digitorum communis, extensor carpi ulnaris, and trapezius muscles. The muscle load of the forearm was significantly less when using the new mouse compared with the traditional one. This was true for the extensor digitorum communis regarding the static (p = .0005) and the median (p = .001) values of the amplitude distribution function (ADF) and the number of periods per minute when the muscle load was below 1% of maximum voluntary contraction (p = .03). The same dear tendency was also found regarding the static muscle load from the extensor carpi ulnaris (p = .06). These results indicate the need for reducing the pronation of the forearm when, working with a mouse.
In a field study, a newly developed mouse that gives the operator a more neutral forearm position was compared with a traditional mouse using a more pronated forearm. After using the new mouse for 6 months, a significant reduction was reported regarding pain intensity and frequency for wrist/hand, forearm, shoulder, and neck (p £ .009). The control group using the traditional mouse reported only small changes in the pain level (p ³ .24). Total duration of pain the last 6 months was also significantly improved for the shoulder and forearm in the intervention group, whereas no such changes were observed in the control group. These results clearly indicate the importance of using a computer mouse with a more neutral position of the forearm.
The aim of this study was to investigate if participants with pain experience reduced pain development when using a mouse allowing a more neutral position of the wrist (Anir) compared with development of pain using a traditional mouse. The study population consisted of 67 participants with mean intensity of pain of approximately 50 mm on a 100-mm Visual Analog Scale (VAS). The total group was randomly divided into 1 intervention group and 1 control group. The study was performed as a prospective parallel group study. VAS was used to assess the average level of pain in the musculoskeletal system during a 6-month period. An earlier article on this study found that after using the Anir mouse for 6 months, a significant reduction was reported in neck pain (48.9 to 33.9). Corresponding data for other areas of the upper extremities were shoulder (54.1 to 31.8), forearm (52.9 to 32.8), and wrist and hand (42.5 to 22.3), respectively (Aarås, Ro, & Thoresen, 1999). The control group using the traditional mouse reported no significant changes in pain level. This article describes the results after giving an identical intervention to were aware of their pain to the start of the study. These results may indicate that musculoskeletal illness is a cumulative traumatic disorder.
In studies on work it is important to assess various subjective symptoms, complaints, and annoyances. To measure such symptoms, psychophysical ratio scales may be used, as along with simpler category rating scales. In this paper some of the basic concepts and methods of psychophysics have been described. In the field of heavy physical work and the perception of effort and exertion, one of the most popular methods is the rating of perceived exertion. This scale has been presented together with a new category ratio scale, commonly referred to as the CR-10 scale. Some situations in which it is important to obtain measurements of perceived exertion have also been described in the paper.
Physical assessment of 146 female workers in highly repetitive jobs found 54% to have evidence of musculoskeletal disorders in the upper limb that are potentially work-related. Many workers had multiple problems, and many were affected bilaterally (33% of workers). Muscle pain and tenderness was the largest problem, both in the neck/shoulder area (31%) as expected and in the forearm/hand musculature (23%), a previously unreported site. Most forearm muscle problems were found on the extensor side. Carpal tunnel syndrome was the most common form of neuritis with 16 people affected (7 people affected bilaterally). De Quervain's tenosynovitis and wrist flexor tendinitis were the most commonly found tendon disorders in the distal forearm (12 people affected for each diagnosis). The results suggest that exposure should be measured bilaterally. They also suggest that muscle tissue is highly vulnerable to overuse. Stressors that affect muscle tissue, such as static loading, should be studied in the forearm as well as in the shoulder.
Cumulative trauma disorders (CTDs) are disorders of the body's tendons and nerves due to repeated exertions and excessive movements. Workers in industrial tasks who have to move their hands and wrists repeatedly and/or forcefully are susceptible to CTDs. One of the major research voids in the study of occupational wrist CTDs is the lack of quantification of the relationship between the known kinematic risk factors, such as wrist angle and repetition, and CTD risk. A quantitative surveillance study was performed in industry in which workers' three-dimensional wrist motions were monitored on the factory floor. A total of 40 subjects from eight industrial plants participated in this study (20 workers in each of two risk groups, low and high). The wrist motion parameters that were monitored for each subject were position, angular velocity, and angular acceleration measures in each plane of movement (radial/ulnar, flexion/extension, and pronation/supination). Descriptive analyses of these measures indicated that generally the mean of the high-risk subjects was larger in magnitude than that of their low-risk counterparts. However, only the velocity and acceleration parameters resulted in significant differences between low- and high-risk groups. These results demonstrate the importance of dynamic components in assessing CTD risk.
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.
Computer mouse use has become an integral part of office work in the past decade. Intensive mouse use has been associated with increased risk of upper extremity musculoskeletal disorders, including carpal tunnel syndrome. Sustained, elevated fluid pressure in the carpal tunnel may play a role in the pathophysiology of carpal tunnel syndrome. Carpal tunnel pressure was measured in 14 healthy individuals while they performed tasks using three different computer mice. Participants performed a multidirectional dragging ('drag and drop') task starting with the hand resting (static posture) on the mouse. With one mouse, an additional pointing ('point-and-click') task was performed. All mice were associated with similar wrist extension postures (p = 0.41) and carpal tunnel pressures (p = 0.48). Pressures were significantly greater during dragging and pointing tasks than when resting the hand (static posture) on the mouse (p = 0.003). The mean pressures during the dragging tasks were 28.8-33.1 mmHg, approximately 12 mmHg greater than the static postures. Pressures during the dragging task were higher than the pointing task (33.1 versus 28.0 mmHg), although the difference was borderline non-significant (p = 0.06). In many participants the carpal tunnel pressures measured during mouse use were greater than pressures known to alter nerve function and structure, indicating that jobs with long periods of intensive mouse use may be at an increased risk of median mononeuropathy. A recommendation is made to minimize wrist extension, minimize prolonged dragging tasks and frequently perform other tasks with the mousing hand.
The aim of this study was to investigate whether gender or different methods of operating a computer mouse have an effect on performance and musculoskeletal load in the use of a computer mouse.
Thirty experienced computer mouse users, 15 men and 15 women, participated in the study. Electromyography (right first dorsal interossei, right extensor digitorum and right and left trapezius), a force-sensing mouse, and subjective ratings were used to register muscular load. An electrogoniometer was used to register the wrist movements. The subjects worked with 3 different methods, their own, a wrist-based method and an arm-based method. Gender comparisons were made when the subjects used their own method.
The women worked with greater extension and range of motion and tended to work with a greater ulnar deviation of the wrist. They also applied higher forces to the mouse when expressed as a percentage of a maximum voluntary contraction and had higher muscular activity in the right extensor digitorum. When using the arm-based method, the subjects worked with greater wrist extension, had higher muscular activity in the right and left trapezius muscles, and had the highest ratings of perceived exertion in the neck and shoulder. The wrist-based method resulted in higher forces being applied to the sides of the mouse and the highest ratings of perceived exertion in the wrist and hand-fingers.
Gender differences were found for musculoskeletal load, and for most of the measured variables the women worked with higher loads than the men. The work method affected performance and musculoskeletal load. Finally, subjective measures appeared to have some utility in characterizing muscular load.
Pronation and supination have been shown to affect wrist goniometer measurement accuracy. The purpose of this study was to compare differences in measurement accuracy between a commonly used biaxial, single transducer wrist goniometer (System A) and a biaxial, two-transducer wrist goniometer (System B) over a wide range of pronation and supination (P/S) positions. Eight subjects moved their wrist between -40 and 40 degrees of flexion/extension (F/E) and -10 and 20 degrees of radial/ulnar (R/U) deviation in four different P/S positions: 90 degrees pronation; 45 degrees pronation; 0 degrees neutral and 45 degrees supination. System A was prone to more R/U crosstalk than System B and the amount of crosstalk was dependent on the P/S position. F/E crosstalk was present with both goniometer systems and was also shown to be dependent on P/S. When moving from pronation to supination, both systems experienced a similar extension offset error; however R/U offset errors were roughly equal in magnitude but opposite in direction. The calibration position will affect wrist angle measurements and the magnitude and direction of measurement errors. To minimize offset errors, the goniometer systems should be calibrated in the P/S posture most likely to be encountered during measurement. Differences in goniometer design and application accounted for the performance differences.
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.
In epidemiological studies of occupational musculoskeletal disorders there is a need for quantitative exposure measurements of the physical work load. In studies of neck and upper limb disorders the so-called cumulative trauma disorders (CTDs), in particular the carpal tunnel syndrome, the positions and movements of the wrist are of special interest. A biaxial flexible electrogoniometer was used to measure continuously, with a sampling rate of 20 Hz, wrist flexion/extension and abduction/adduction angles up to 27 min. Evaluation of the influence of rotation on the goniometer showed some inherent crosstalk, which, however, did not invalidate the results. For occupational repetitive work, 99.5% of the signal power was contained in the 0-5 Hz band. Two-dimensional angle distributions and power spectra gave comprehensive information about wrist postures and movements. Measures reflecting both static and dynamic properties were derived from time and frequency domains. These measures give quantitative information on different potential risk factors and are therefore useful in epidemiological studies. Mean power frequency (MPF) is suggested as a generalized measure of repetitiveness. The method was applied in field studies of fish processing industry workers with highly repetitive work and risk of CTD.
Surface electromyographic (EMG) amplitude from the upper trapezius muscle is widely used as a measure of shoulder-neck load in ergonomic studies. A variety of methods for normalizing EMG amplitude from the upper trapezius (EMGamp(ut)) have been presented in the literature. This impedes meta-analyses of, for instance, upper trapezius load in relation to development of shoulder-neck disorders. The review offers a thorough discussion of different normalization procedures for EMGamp(ut). The following main issues are focused: output variable, location of electrodes, posture and attempted movement during normalization, load and duration of reference contractions, signal processing and test-retest repeatability. It is concluded that translations of EMGamp(ut) into biomechanical variables, for example relative force development in the shoulder or in the upper trapezius itself, suffer from low validity, especially if used in work tasks involving large and/ or fast arm movements. The review proposes a standard terminology relating to normalization of EMGamp(ut) and concludes in a concrete suggestion for a normalization procedure generating bioelectrical variables which reflect upper trapezius activation.
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.
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.
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.
Epidemiologic and experimental studies were reviewed to assess the role of postural factors, high handgrip and pinch forces, repetitive hand and wrist movements, external pressure, and vibration in the occurrence of carpal tunnel syndrome (CTS). Forceful repetitive work, vibration, and extreme wrist postures have been associated with CTS in several epidemiologic studies. Experimental studies have shown that certain forearm, wrist, and finger postures, even moderate hand loads and external pressure on the palm, can increase carpal tunnel pressure (CTP) at least temporarily to levels at which nerve viability is threatened. It is concluded that while more research is needed, there is sufficient information to suggest that reducing the duration, frequency or intensity of exposure to forceful repetitive work, extreme wrist postures and vibration is likely to result in a reduction of the incidence or severity of CTS in working populations.
The physiologically tolerable range of positions for the joints of the upper extremities have been investigated for typing tasks by recording the myoelectric activities of the involved muscles. For long-term typing tasks a split keyboard is recommended allocating a key field to each hand. The fields should be rotated against each other in the horizontal plane and inclined laterally.
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