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PubMed2006

Effects of a thermal-insulating mouse pad on temperature of forearm and hand during computer tasks.

This laboratory experiment studied the effects of a thermal-insulating mouse pad on arm temperature and comfort during computer work. Fourteen subjects performed two 20-min computer tasks (a mouse task and a combined task alternating keyboard and mouse use), under three conditions, namely with: 1) a thermal-insulating pad; 2) a placebo pad; 3) no pad (desktop). The temperatures of the forearm, wrist, hand and fingers were measured with four thermocouples. Comfort and discomfort were determined by two visual analogue scales. No arm temperature differences were found between the experimental conditions after performing the combination task in any location. After the mouse task, however, arm temperature decreased significantly less with the thermal-insulating mouse pad than with the placebo pad. The thermal-insulating pad was rated as more comfortable and less uncomfortable than a regular desktop during mouse tasks. A large size is recommended for the thermal-insulating pad.

Adult↗
PubMed2006

Effect of keyswitch design of desktop and notebook keyboards related to key stiffness and typing force.

This study aimed to compare and analyse rubber-dome desktop, spring-column desktop and notebook keyboards in terms of key stiffness and fingertip typing force. The spring-column keyboard resulted in the highest mean peak contact force (0.86N), followed by the rubber dome desktop (0.68N) and the notebook (0.59N). All these differences were statistically significant. Likewise, the spring-column keyboard registered the highest fingertip typing force and the notebook keyboard the lowest. A comparison of forces showed the notebook (rubber dome) keyboard had the highest fingertip-to-peak contact force ratio (overstrike force), and the spring-column generated the least excess force (as a ratio of peak contact force). The results of this study could aid in optimizing computer key design that could possibly reduce subject discomfort and fatigue.

Adult↗
PubMed1995

Computer mouse use and cumulative trauma disorders of the upper extremities.

The computer mouse is now present in virtually every office environment because of the recent adoption of the graphical user interface. However, Karlqvist et al. (1994) pointed out that there still remains a paucity of work on the musculoskeletal problems associated specifically with computer mouse use. Likewise, there have been no published data on the magnitude of upper extremity musculoskeletal disorders associated with computer mouse use. In order to ascertain this magnitude, claims data from the Liberty Mutual Group were reviewed for the years 1986 to 1993, inclusive. Count, total cost and average cost per claim for all claims associated with computer use and computer mouse use were determined for the years in question. It was concluded that although there are few claims related to computer mouse use, it appears to be a growing problem, and therefore, perhaps, deserves more research and intervention attention. However, the present magnitude is less than for other musculoskeletal disorders.

Arm↗
PubMed1997

Surface electromyography and mouse use position.

This study examines muscle tension and subjective muscle tension awareness while using a computer mouse positioned to the right of a standard computer keyboard and a centrally positioned trackball. Seventeen volunteer subjects experienced in mouse and trackball use were seated at an ergonomically adjusted workstation. Surface electromyography (sEMG) and subjective muscle tension levels were recorded from four muscle groups (left sternocleidomastoid/scalene, right upper trapezius, right posterior deltoid, and right lower trapezius/rhomboids) during 1-min trials with subjects resting with hands in their lap, while using a trackball below the centre of the keyboard, and while using a mouse immediately to the right of a 101-key keyboard. All subjects showed significantly higher mean sEMG activity recorded from the right upper trapezius, right posterior deltoid, and right lower trapezius/rhomboids during mouse use to the right of a standard keyboard (arm abducted) compared to using a trackball positioned centrally, (p < 0.001). sEMG levels remained elevated during the entire trial period of right side mouse use without evidence of microbreaks (< 1 s epochs of low sEMG activity). sEMG activity from the left sternocleidomastoid/scalene muscles showed no significant change from baseline in any condition. Subjective reports of muscle tension did not correlate with sEMG activity. The authors predict that there will be an overall increase in reports of upper extremity musculoskeletal disorders (UEMSD) and computer related disorders (CRD) when people abduct their arms in order to reach a mouse positioned to the side of standard width, or wider keyboards. Discussed are the applications of sEMG for evaluation of computer keyboard and pointing device use, appropriate ergonomic equipment design, and a methodology for improving muscle awareness, strengthening, relaxation, and workstyle practices to promote healthier computing.

Adult↗
PubMed1997

The effect of keyboard keyswitch make force on applied force and finger flexor muscle activity.

The design of the force-displacement characteristics or 'feel' of keyboard keyswitches has been guided by preference and performance data; there has been very little information on how switch 'feel' alters muscle activity or applied force. This is a laboratory-based repeated measures design experiment to evaluate the effect of computer keyboard keyswitch design on applied finger force and muscle activity during a typing task. Ten experienced typists typed on three keyboards which differed in keyswitch make force (0.34, 0.47 and 1.02 N) while applied fingertip force and finger flexor electromyograms were recorded. The keyboard testing order was randomized and subjects typed on each keyboard for three trials, while data was collected for a minimum of 80 keystrokes per trial. No differences in applied fingertip force or finger flexor EMG were observed during typing on keyboards with switch make force of 0.34 or 0.47 N. However, applied fingertip force increased by approximately 40% (p < 0.05) and EMG activity increased by approximately 20% (p < 0.05) when the keyswitch make force was increased from 0.47 to 1.02 N. These results suggest that, in order to minimize the biomechanical loads to forearm tendons and muscles of keyboard users, keyswitches with a make force of 0.47 N or less should be considered over switches with a make force of 1.02 N.

Adult↗
PubMed1998

Directional stimulus-response compatibility: a test of three alternative principles.

The basis of directional stimulus-response compatibility was studied using a task in which 128 participants moved a cursor into targets with a joystick, resembling the operation of certain industrial and construction equipment. Compatible and incompatible versions of three alternative compatibility principles were compared in all combinations. Visual Field (VF) compatibility was present if cursor and controlling limb movement were in the same direction in the visual field, Control Display (CD) compatibility meant that the control motion was in the same direction as, and parallel to, cursor motion, and Muscle Synergy (MS) compatibility was defined as use of the muscle synergy normally associated with the required direction as seen in the visual field. VF-compatible conditions had significantly shorter reaction, movement and homing times, and fewer reversal errors, for males and females, in two testing sites. These advantages were maintained over practice. VF compatibility was confirmed as a robust spatial compatibility principle that is affected by neither the orientation of the operator's limb or head nor the muscle synergy used in executing the task. It offers not only more rapid performance, but also a markedly reduced rate of potentially dangerous directional errors. The relationship between this finding and theoretical aspects of stimulus-response compatibility is discussed.

Adult↗
PubMed1999

Effects of keyboard tray geometry on upper body posture and comfort.

The effects of a downward-tilting (DT) keyboard tray on wrist posture, seated posture and self-assessed musculoskeletal discomfort were investigated in a field experiment. Thirty-eight professional office workers were studied. A pretest assessed how they typed using either a conventional keyboard on a desk or on an articulating keyboard tray, and with or without wrist rests. Workers were randomly allocated to a control (n = 15) or test group (n = 23) that used their existing keyboard in a DT system. A post-test was conducted 3 weeks later. Results showed no significant changes in wrist posture, seated posture or reports of musculoskeletal discomfort for the control group, and approximately 50% of typing wrist movements put the hand in a neutral zone. There were significant improvements in wrist posture, seated posture and upper body musculoskeletal discomfort for the test group using the DT system. Over 80% of typing wrist movements put the hand into a neutral zone with the DT arrangement. Reactions to using a conventional keyboard on a DT system were positive.

Adult↗
PubMed1999

Effects of computer mouse design and task on carpal tunnel pressure.

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.

Adult↗
PubMed2003

Digestible energy intake, dry matter digestibility and effect of increased calcium intake on bone parameters of grazing Thoroughbred weanlings in New Zealand.

AIMS: To measure the nutritive value of pasture in terms of digestible energy intake (DEI) and dry matter (DM) digestibility, and the effects of increased calcium (Ca) intakes on apparent mineral absorption and bone characteristics in grazing weanling Thoroughbreds. METHODS: DM intake (DMI) and DEI were determined in 16 weanling Thoroughbreds grazing pasture from their daily faecal DM output, measured over 8 days, divided by the DM indigestible fraction (1-digestible DM) determined in a 6-day digestibility trial. The DM, gross energy content, crude protein, soluble carbohydrate, acid detergent fibre, neutral detergent fibre, lipid, Ca, phosphorus (P), sodium (Na), potassium(K), sulphur (S) and magnesium (Mg) composition of perennial ryegrass/white clover pasture and faeces were determined and their digestibility and/or apparent absorption calculated. Calcium intake and bone growth studies used 17 weanlings, randomly divided into three groups and fed perennial ryegrass/white clover pasture and 0.5 kg grain, with or without a CaCO3 supplement, for 84 days. The animals in Group 1 (n=6) were on a low Ca diet (3.5 g/kg DM) and were fed pasture only; those in Group 2 (n=5) were on a medium Ca diet (6.3 g/kg DM);and those in Group 3 (n=6) were on a high Ca diet (12.0 g/kg DM). After 44 days the apparent absorption of Ca was determined from the differences between the Ca intakes and faecal Ca outputs. At periods just before and after Ca supplementation the horses were anaesthetised and the left radius, third metacarpus(Mc3) and first phalanx of the left foreleg were scanned using a peripheral quantitative computed tomography scanner to determine cortical mineral content, density, area, periosteal circumference and bone strength. To investigate gastrointestinal tract transit time and DM digestibility, five randomly selected horses were administered Swiss screen bags on several occasions via a nasogastric tube. Each 60 x 10mm bag contained 3.21 (SE 0.37) g of frozen minced grass. Bags were recovered from the freshly passed faeces and frozen until analysis. RESULTS: The DM digestibility of the pasture was 0.62, while the DMI and DEI of weanlings (300 kg, gaining 0.7 kg/day) were 5.5 kg/day and 63 MJ/day, respectively. Increasing Ca intake had no significant effect on DEI, DM digestibility or on the apparent absorption of Ca, P, Na and K, but decreased the apparent absorption of Mg from 0.50 to 0.38. Regardless of Ca intake, the apparent absorption of Ca was 0.56. During the Ca administration trial there were significant increases overtime in the bone strength (strain stress index) of the proximal phalanx, Mc3 and radial diaphysis. However, the increase in bone strength was not associated with increase in dietary Ca, as neither the medium- nor high-Ca intake groups differed significantly from the low-Ca controls. The mean transit time for the Swiss screen bags was 25.46 (SE 0.09) h, and transit times were similar whether the horses were grazing or confined in loose boxes, being 26.64 (SE 0.23) h and 24.33 (SE 0.13) h, respectively. The DM digestibility determined using the bags was 0.54, which was significantly lower than the 0.62 determined by direct faeces collection. CONCLUSIONS: Good growth rates were achieved in Thoroughbred weanlings grazing perennial ryegrass/white clover pasture containing 3.5 g Ca/kg DM and a DE of 11.4 MJ/kg DM. Increasing dietary Ca intake 3.5-fold for 3 months had negligible impact on bone growth and development.

Journal Article↗
PubMed2003

Assessment of the risk of physical contamination of bread packaged in perforated oriented polypropylene films: measurements, procedures and results.

Perforated films used for wrapping factory-manufactured bread must permit a very rapid and intense moisture exchange because the packaging operation is carried out while the bread is still warm (about 80 degrees C) and releasing a high quantity of moisture. The open surface of the wrapping of those products sold in self-service retail outlets generates suspicion about possible contamination of bread not properly handled by the consumers and a better knowledge of the performance of these materials seems appropriate. Using two different approaches, the geometrical characteristics and perforation pattern of 13 different oriented polypropylene (OPP) films representative of the whole European market were assessed objectively. All the measured parameters (density of perforation, hole dimension, open surface, etc.) showed asymmetric distributions, i.e. with averages close to the lowest figures. Similar asymmetric distribution was shown from the 'risk of contamination' by artificial sweat and saliva: an empirical parameter which was measured by procedures developed to simulate the worst possible case of inappropriate manipulation of the packed bread. Good correlation was found between the 'risk of contamination' and both the 'hole surface' (mm(2)) and the 'open surface' (percentage holes surface/film surface), leading to the conclusion that the proposed procedures could represent useful methodologies for assessment of such a particular case of possible food contamination.

Bread↗
PubMed2003

A pilot study exploring electronic (or e-mail) mail in users with acquired cognitive-linguistic impairments.

This paper reports the results of an exploratory study into the usability of a simplified e-mail interface for eight individuals with acquired cognitive-linguistic impairments. Participatory Action Research, a qualitative research method, was used to capture the range of performance variables and to emphasize a 'user-centred' approach to the research process. The participants were asked to read and reply to e-mails across four writing prompt conditions. An analysis of errors and participant preferences for the prototype e-mail system was conducted. Errors fell into two general categories: (1) computer usability (e.g. conceptual understanding of mouse/cursor operation) and (2) message composition (e.g. generating ideas for a message). Participant preferences for the writing prompt conditions varied considerably. All participants endorsed the use of customized e-mail interfaces as a means of connecting with friends and family, thereby reducing social isolation. Implications for interface design, rehabilitation and future research into assistive technology are discussed.

Adult↗
PubMed2003

The independence of response structure and element production in timing sequences.

In three experiments, participants were asked to produce a prescribed temporal sequence of key presses. The number of elements in a key press sequence, the movement time of the elements, and uniformity of the timing elements comprising the sequence were manipulated. If the processing of the sequence structure was independent of the processing of elements comprising the sequence, increasing the number of the elements in the sequence should affect the production of the sequence but not the proficiency with which the individual elements are, produced. Increasing the movement time of the elements, however, should affect the production of the elements but have little, if any, effect on the integrity of the sequence. The findings indicated that increasing the number of elements negatively affected sequence production when the elements were nonuniform but had little or no effect when elements were uniform. Alternatively, element production was affected by movement time but not number of elements. The results of these experiments appear to confirm the independence of sequence and element production. However, Experiment 3, in which the uniformity of the elements was directly contrasted, found strong evidence for coarticulatory influences in the learning processes, whereby the longer and shorter than average elements in the sequence negatively affected the sequence integrity and the production of the individual elements. When faced with a nonuniformn timing pattern, participants appear to elongate or shrink individual elements of a uniform timing pattern to fit the desired sequence requirements. The result is that the longer or shorter than average elements require more practice to produce correctly, tend to regress across retention intervals, and are generally less stable than the elements nearer the average.

Adult↗
PubMedDate not supplied

Variation in bone mineral density in adults in Poland: age and sex differences.

The decline of mineral bone density with age can lead in more extreme cases to osteopenia and osteoporosis, and is therefore one of the aspects of ageing with great medical and social significance. With this idea in mind a study of age changes in the trabecular and, separately, the cortical bone density of the radius was carried out in 1218 females and 405 males, aged 22 to 60 years, all occupationally active inhabitants of the city of Wroclaw, Poland. The technique used was the peripheral Quantitative Computed Tomography (pQCT). It was found that in females bone densities remain relatively stable throughout the period between 22 and 40 years. They then begin to decline slowly, with a rapid decline after the age of 55. A distinctly different pattern was found among males, with bone densities reaching peak values, markedly higher than those in females, in the third decade of life. After this age the bone density values begin to decline at a rapid rate, so that by the age of 60 years mean trabecular and cortical densities in males have decreased to levels almost equivalent to females of equal age. In view of the small size of the male samples, especially in the older age classes, the above results should be treated with caution and confirmed using larger samples.

Adult↗
PubMedDate not supplied

The inverse relationship between bone status and blood pressure among Polish men.

PRIMARY OBJECTIVE: An evaluation of relationships between bone density and blood pressure in healthy men. RESEARCH DESIGN: A cross-sectional population-based survey. METHODS AND PROCEDURES: An ethnically homogeneous sample of 208 men, aged 35-63, healthy and occupationally active inhabitants of the city of Wroclaw, Lower Silesia, Poland were studied. Trabecular, cortical and total bone mineral content (BMC) at the ultra-distal radius of the non-dominant hand were assessed by peripheral Quantitative Computed Tomography (pQCT: Stratec 960 apparatus). Body mass index (BMI) was used as a measure of general obesity. Systolic and diastolic blood pressure (BP) were measured using an MPC-350 sphygmomanometer. Multiple linear regression was used to evaluate the relationships between BP and BMC. A two-way analysis of covariance was carried out to test for the significance of inter-group differences in BMC with regard to age and BP with BMI as a contiuous covariable. Multiple logistic regression was used to verify whether some select factors (age, BMI, systolic and diastolic BP) could significantly predict male bone status. RESULTS: Systolic BP was not related to bone status at the ultra-distal radius. There were no differences in any BMC between systolic hyper- and normotensive subjects. Additionally, systolic hypertension did not affect the probability of an occurrence of male osteopenia (independently of age and BMI). In contrast, there were significant negative relationships between diastolic BP, and trabecular and total (but not cortical) BMC (even when controlled for age and BMI). Moreover, diastolic hypertensive men had reduced BMC at the ultra-distal radius when compared with normotensive subjects. It is noteworthy that Polish men of diastolic BP exceeding 90 mmHg had an approximately 1.50-fold increased relative risk of being osteopenic when compared with normotensive subjects (even when controlled for age, BMI and systolic BP). CONCLUSIONS: In the light of the inverse relationship between BMC and diastolic BP, Polish men with elevated diastolic BP seem to be more prone to the excessive age-related bone loss.

Adult↗
PubMed1991

Comparing three head-pointing systems using a single subject design.

The keyboard is the most commonly used input method for interfacing with computers. When using a keyboard is not possible, alternative computer input methods are needed. Three methods using head control are: Head Master by Prentke Romich, Free Wheel by Pointer Systems, and LROP by Words+. The purpose of this study was to compare these three methods for speed and accuracy using a single subject design for nine individuals with disabilities. Visual inspection of the data revealed that subjects obtained higher scores when using Head Master and LROP than Free Wheel. As a follow-up test, an analysis of variance test for repeated measures showed no difference between using Head Master and LROP but did show a significant difference between Head Master and Free Wheel, and LROP and Free Wheel.

Adult↗
PubMed1991

A pilot study comparing mouse and mouse-emulating interface devices for graphic input.

Adaptive interface devices make it possible for individuals with physical disabilities to use microcomputers and thus perform many tasks that they would otherwise be unable to accomplish. Special equipment is available that purports to allow functional access to the computer for users with disabilities. As technology moves from purely keyboard applications to include graphic input, it will be necessary for assistive interface devices to support graphics as well as text entry. Headpointing systems that emulate the mouse in combination with on-screen keyboards are of particular interest to persons with severe physical impairment such as high level quadriplegia. Two such systems currently on the market are the HeadMaster and the Free Wheel. The authors have conducted a pilot study comparing graphic input speed using the mouse and two headpointing interface systems on the Macintosh computer. The study used a single subject design with six able-bodied subjects, to establish a baseline for comparison with persons with severe disabilities. Results of these preliminary data indicated that the HeadMaster was nearly as effective as the mouse and that it was superior to the Free Wheel for graphics input. This pilot study, however, demonstrated several experimental design problems that need to be addressed to make the study more robust. It also demonstrated the need to include the evaluation of text input so that the effectiveness of the interface devices with text and graphic input could be compared.

Adult↗
PubMed2001

Efficiency of the Chubon versus the QWERTY keyboard.

There is little available evidence for claims of the efficiency of alternative keyboard layouts. Part of the difficulty in providing such evidence is that available research subjects typically have extensive experience with the standard keyboard, making a fair comparison of keyboard layouts difficult. The purpose of this study was to provide a true comparison of the QWERTY and Chubon keyboard layouts for individuals who type with a single digit by neutralizing prior experience through an inversion of the QWERTY keyboard. A single-subject, repeated measures design was used with a convenience sample of nine participants. Each participant began typing on a preselected keyboard and continued typing until fluency was achieved. This procedure was replicated with each keyboard layout. The words per minute typed at fluency for the Reverse QWERTY was approximately 62% of the QWERTY, indicating that the learned effect had been erased. The average typing speed of the Chubon was at least 5% higher and at most 51% higher than the Reverse QWERTY. There were no significant patterns of error. Results of this study indicate that the biomechanical layout of the Chubon is superior to that of the Reverse QWERTY and, by extension, to that of the QWERTY. Additional research is needed to expand knowledge of the effectiveness of the various alternative keyboard layouts.

Computer Peripherals↗
PubMed2006

Comparison of three computer office workstations offering forearm support: impact on upper limb posture and muscle activation.

The aims of the study were: 1) to determine whether resting the forearms on the work surface, as compared to chair armrests, reduces muscular activation; 2) to compare the sensitivity of different electromyographic (EMG) summary parameters. Eighteen healthy subjects performed computer work (with keyboard and mouse alternately) for 20 min while resting their forearms on a work surface adjustable in height (Workstation A), on the chair's armrests with an adjustable workstation (Workstation B) or on their chair's armrests with a non-adjustable workstation (Workstation C). The EMG amplitude of the trapezius and deltoid muscles was little influenced by the workstations, whereas their EMG variability increased with Workstation A, which was interpreted as a positive effect. However, the EMG amplitude of the mouse-side extensor digitorum muscle was higher with Workstation A. Alternating between resting the forearms on the work surface and on the chairs' armrests could solicit different muscles during computer work, and could be considered as a strategy for preventing musculoskeletal disorders. The new exposure variation analysis summary parameters used were sensitive to small workstation changes, thus supporting their use in future studies.

Adult↗