Kinematic analysis of the traditional keyboard typing in computers using different inclinations (original) (raw)
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The effect of six keyboard designs on wrist and forearm postures
Applied Ergonomics, 2007
There is increasing evidence that alternative geometry keyboards may prevent or reduce arm pain or disorders, and presumably the mechanism is by reducing awkward arm postures. However, the effect of alternative keyboards, especially the new designs, on wrist and arm postures are not well known. In this laboratory study, the wrist and forearm postures of 100 subjects were measured with a motion analysis system while they typed on 6 different keyboard configurations. There were significant differences in wrist extension, ulnar deviation, and forearm pronation between keyboards. When considering all 6 wrists and forearm postures together, the keyboard with an opening angle of 121, a gable angle of 141, and a slope of 01 appears to provide the most neutral posture among the keyboards tested. Subjects most preferred this keyboard or a similar keyboard with a gable angle of 81 and they least preferred the keyboard on a conventional laptop computer. These findings may assist in recommendations regarding the selection of keyboards for computer usage. r
Keyboard Design? Postural behavior evaluation during interaction with keyboards and typewriters
2008
The study has evaluated macro and micro postural analysis and angular relationships of the main anatomical segments involved in the activity of typewriting in old typewriters and current computer keyboards. Our protocol consider this objects with the goals to identify and to rescue structural benefits of the old typewriters that were not incorporated in the current design of keyboards for computers, as well as those activities' aspects and properties. As results, we have that some old typewriters' attributes which were not considered for the design of new computer keyboards can contribute to reduce the wrist overload.
Effect of four computer keyboards in computer users with upper extremity musculoskeletal disorders
American Journal of Industrial Medicine, 1999
Eighty computer users with musculoskeletal disorders participated in a 6-month, randomized, placebo-controlled trial evaluating the effects of four computer keyboards on clinical findings, pain severity, functional hand status, and comfort. The alternative geometry keyboards tested were: the Apple Adjustable Keyboard [kb1], Comfort Keyboard System [kb2], Microsoft Natural Keyboard [kb3], and placebo. Compared to placebo, kb3 and to a lesser extent kb1 groups demonstrated an improving trend in pain severity and hand function following 6 months of keyboard use. However, there was no corresponding consistent improvement in clinical findings in the alternative geometry keyboard groups compared to the placebo group. Overall, there was a significant correlation between improvement of pain severity and greater satisfaction with the keyboards. These results provide evidence that keyboard users may experience a reduction in hand pain after several months of use of some alternative geometry keyboards. Am.
Applied Ergonomics, 2009
The effects of forearm and wrist supports on the upper extremity postures in computer keying tasks and associated EMG activity of arm and back muscles were examined (N ¼ 8). Four positions were forearms unsupported (floating) and supported, wrists supported by bead packed (WR1) and gel-filled (WR2) wrist rest. The right and left elbow extensions were 651 and 681, respectively, in unsupported forearms. Bilateral elbow extension increased with the forearm/wrist supports and mostly, the elbow was maintained at around 901 or greater. The wrist extension decreased with forearm/wrist supports over the unsupported condition. The forearm support significantly reduced the activity of forearm extensor digitorum, i.e., right (F (1, 47) ¼ 12.19, po0.01) and left (F (1, 47) ¼ 5.38, po0.05) and upper trapezius muscles over the floating posture. Wrist rests, however, increased load on the upper trapezius; the activities of flexor digitorum superficialis and erector spinae were close to the resting EMG activity for both forearm and/or wrist support. The type of wrist rests was a concern and this study indicated that the gel filled wrist rest was advantageous in reducing the forearm muscle load, in comparison to the bead packed cushions.
An assessment of alternate keyboards using finger motion, wrist motion and tendon travel
Clinical Biomechanics, 2000
Objective. To assess the biomechanical impact of commercially available alternate keyboard designs. Design. A repeated measures study was conducted in a laboratory setting, with planned comparisons of Pitch, Roll and Yaw angles of the keyboards. Ten keyboard conditions were tested. Dependent measures included tendon travel, wrist deviations, and wrist and ®nger kinematics. Background. Various alternate keyboard designs have recently been introduced, which vary Pitch, Roll and Yaw angles, separation distance between keyboard halves, and include other novel features such as cup-shaped depressions for the keys. Yet little objective research has been conducted regarding the biomechanical implications of these various design features. This study attempts to quantify the keyboard designs in terms of several recognized risk factors associated with cumulative trauma disorders that arise with repetitive typing. Methods. Wrist and ®nger goniometers were used to measure joint motions during a standardized typing task. 15 experienced typists (8 women, 7 men) served as subjects. Regression equations were used to generate estimates of tendon travel. Results. Tendon travel was aected primarily by Pitch but not Roll or Yaw angles while wrist deviations responded to changes in all three angles. Males had signi®cantly greater amount of tendon travel than female subjects; this dierence was only partially accounted for by anthropometry. Dierences in joint motion may have a greater impact on the amount of tendon travel. Conclusions. Alternate keyboard designs can aect tendon travel by as much as 11%. Relevance As various alternate keyboard designs are marketed, quanti®able biomechanical data such as that provided by this study, will help to assess their impact on the risk factors for cumulative trauma disorders.
Applied Ergonomics, 2004
Forearm support during keyboard use has been reported to reduce neck and shoulder muscle activity and discomfort. However, the effect of forearm support on wrist posture has not been examined. The aim of this study was to examine the effect of 3 different postures during keyboard use: forearm support, wrist support and ''floating''. The floating posture (no support) was used as the reference condition. A wrist rest was present in all test conditions. Thirteen participants completed 20 min wordprocessing tasks in each of the test conditions. Electromyography was used to monitor neck, shoulder and forearm muscle activity. Bilateral and overhead video cameras recorded left and right wrist extension, shoulder and elbow flexion and radial and ulnar deviation. The forearm support condition resulted in significantly less ulnar deviation (op ¼ 0:007), less time spent in extreme ulnar deviation (p ¼ 0:002) and less reports of discomfort than the ''floating'' condition (p ¼ 0:002). The wrist support but not the forearm support condition resulted in less trapezius and anterior deltoid muscular activity (po0:007). These findings indicate that typing with upper extremity support in conjunction with a wrist rest may be preferable to the ''floating'' posture implicit in current guidelines. r
Finger motion, wrist motion and tendon travel as a function of keyboard angles
2000
Objective. This study assessed the impact of keyboard angles (in terms of Pitch, Roll and Yaw) on tendon travel and wrist and ®nger joint kinematics for the¯exor digitorum profundus and¯exor digitorum super®cialis. Design. A repeated measures, laboratory study was conducted. Independent variables were three Pitch angles, three Roll angles, three Yaw angles, and three keyboard separation distances. Dependent variables were tendon travel, wrist deviation, wrist and ®nger joint kinematics, and Borg comfort rating. Background. The increased usage of computers and the risk of cumulative trauma disorders have led to the development of alternate keyboards. This study is a biomechanical assessment of several keyboard designs. Methods. Lightweight wrist and ®nger goniometers were used to measure motion of the wrist in three planes, and for three ®nger joints. Fifteen experienced typists (eight women, seven men) typed a standard text on 30 keyboard conditions. Regression equations were used to calculate tendon travel from joint positions. Results. Tendon travel is sensitive to changes in Pitch, Roll and Yaw angles with 13% dierence between the minimal and maximal tendon travel. A¯at keyboard produced more tendon travel than keyboards with greater Pitch and Roll angles. Conclusions. There is a trade-o between wrist and ®nger positions; as the wrist extends more, the ®nger joints¯ex more to compensate. Keyboards imposed dierent trade-os between the wrist and ®nger positions, aecting the overall tendon travel. Relevance Alternate keyboard designs can signi®cantly aect tendon travel and may address reduced repetitiveness in typing by reducing the amount of tendon travel.
Effects of a Multitouch Keyboard on Wrist Posture, Typing Performance and Comfort
PsycEXTRA Dataset, 2005
The design of computer keyboards is rapidly evolving as portable computing becomes increasingly ubiquitous due to wireless networking and the increased popularity of personal digital assistants and notebook computers. However, there is a balance between mobility and productivity, in terms of text-entry accuracy and speed, which needs to be maintained as computer keyboards become smaller and slimmer through the introduction of ultra low-profile designs. In addition, the ergonomic benefits, in terms of the reduction of awkward wrist postures and user comfort, of ultra-low profile designs are unclear. This study tests a new prototype ultra-low profile MultiTouch keyless keyboard (MTK) that uses a MultiTouch surface to create an extremely thin typing environment that requires no force to register a keystroke and allows mousing and gestural input on the same surface. In this study, the MTK was tested against a conventional keyboard (CK) for typing speed, accuracy, wrist postures and user comfort. It was hypothesized that the lack of key travel would increase speed and accuracy, while the ultra-thin design would reduce the amount of wrist extension, which could decrease the risk of a wrist injury or other hand and wrist musculoskeletal disorder. Finally, it was hypothesized that there would be a significant short-term learning effect on typing speed and accuracy for the MTK. A laboratory experiment was conducted with 6 males and 6 females typing using two QWERTY keyboard designs: a CK and a MTK. Subjects visited the lab for 1.5 hours for 2 non-consecutive days in the same week, for a total of 3 hours. Each visit consisted of eight randomly assigned 7.5-minute typing tasks of text passages of similar difficulty and identical length. Quantitative measures of typing speed and accuracy were collected using Typing Quick and Easy 13.0 and qualitative measures of user preference and comfort were gathered by self-report questionnaires. A wrist glove electrogoniometer system was used to record right-hand wrist positioning data, which was analyzed to assess the risk of injury. The two keyboards were evaluated in a repeated measures withinsubjects factorial design. Subjects, typed slower (F 1,11 = 41.86, p=0.000) and less accurately (F 1,11 = 23.55, p=0.001) on the MTK during the typing tasks. Subjects preferred the CK and reported a higher level of ease (F 1,11 = 49.732, p=0.00) and enjoyment (F 1,11 = 51.129, p=0.00) during its use. Mean wrist extension was lower for the MTK (F 1,11 = 10.205, p=0.000) while radial and ulnar deviation did not differ significantly between the two keyboards. The MTK had a lower percentage of highest-risk wrist extension (F 1,11 = 6.437, p=0.028), and conversely, a higher percentage of neutral wrist posture (F 1,11 = 12.947, p=0.004). A significant positive linear trend was observed across the within-subjects scores for speed (F 1,11 = 9.308, p=0.011) and accuracy (F 1,11 = 11.903, p=0.005) across tasks in the MTK condition. Limitations to this study include practice effects, due to the naïve subjects' lack of training on the MTK and the limited duration of exposure to this novel keyboard. Fatigue effects may have also been a factor, even though the experimental conditions were spread out over two non-consecutive days in the same week. Future research directions include additional testing of the unique mousing and gestural capabilities of the MTK. Other research suggests that practice and extended exposure to the MTK may raise performance to comparable levels associated with CK devices.
Factors related to working posture and its assessment among keyboard operators
Applied Ergonomics, 1991
Video analysis of 15 keyboard operators was conducted over two four-hour periods to determine the effects of symptoms of over-use injury, the adjustability of the workstation, the type of keyboard, time of day and sex on working posture. The only factor which significantly affected posture was the type of keyboard, with operators at typewriters adopting a more extended shoulder position, reduced elbow flexion and increased wrist flexion, than those working at a VDU terminal. Analysis of the components of variance associated with repeated observations revealed that to minimise the variance associated with recording the posture of these subjects, and therefore obtain a representative mean posture, required at least nine observations for wrist angle, four for elbow angle, six for shoulder angle and three for trunk incline. The mean posture adopted by this group of operators was similar to the 'right angles' posture, with the trunk reclined 4 °, shoulder extended 1 °, elbow 92 ° and wrist extended 7 ° .