Alternative computer mouse design and testing to reduce finger extensor muscle activity during mouse use

Alternative to Reduced Stresses on the Upper Extremity in a Standing Workstation

OBJECTIVE

This study evaluated a standing armrest to provide more acceptable ergonomic guidelines that may reduce the cost of standing computer workstations.

BACKGROUND

Of the many advantages of standing workstations, there have been no efforts to minimize the biomechanical cost, such as larger wrist extension and greater forearm muscle activity than sitting.

METHOD

Sixteen participants were asked to perform a typing task under a combination of the following factors: (1) desk shape (rectangular and concave); (2) desk height (0, +5, -5 cm from 90° elbow flexion); and (3) monitor height (0, -10 cm from the eyes). During the trials, the trunk kinematics, muscle activation levels, and CoP were recorded.

RESULTS

Both arms were further away from the upper body under the concave and +5 desk height than under the normal condition, but significant decreases in the extensor carpi radialis (8.6%), anterior deltoid (28.8%), and L4 paraspinals (5.5%) were observed. Similarly, the wrist extension angle decreased by 10.5° (42%) under this condition, but the posture required a 2.2° (19%) increase in wrist adduction angle. The CoP irregularity was greater under the concave workstation, indicating more complex motion.

CONCLUSION

A higher and concave desk can provide an armrest effect while engaged in a standing workstation by reducing the wrist extension and related muscle activation level, but at the cost of a larger wrist adduction angle.

APPLICATION

Providing a standing armrest (+5 cm height and concave desk) could reduce the stresses on the upper extremities, but a split keyboard should be considered to minimize wrist adduction.

Dynamics of forearm muscle activity in slanted computer mice use

BACKGROUND

Static muscular activity of muscles activated in the use of the conventional PC mouse is believed to represent a higher risk for the musculoskeletal health of the user than dynamic muscular activity.

OBJECTIVE

This paper presents a compounded muscular activity dynamics indicator (akin to percent relative range), enabling comparison between computer handheld pointing devices.

METHODS

This muscular dynamism approach considers baseline muscular activity (APL, ECR, ECU and ED) relative to the Maximum Voluntary Contraction as well as the dynamics of muscular activation. The latter is computed as the ratio of the difference between APDF90 and APDF10 divided by APDF50 (APDF-Amplitude Probability Distribution Function for the 90th, 50th and 10th percentiles). The paper demonstrates the approach with results of comparative evaluation of a horizontal, a slanted and a vertical PC mouse, through surface EMG monitoring of 20 participants performing standardized graphical task with the devices.

RESULTS

Hand size impacts muscular activity dynamics in these four muscles, which supersedes differences in device geometry, across the range of devices tested.

CONCLUSION

Smaller devices relative to hand size foster more dynamic muscular activity.

Usability Evaluation of Slanted Computer Mice

Prevention of musculoskeletal disorders is supported by use of slanted rather than horizontal pointing devices, but user acceptance of the former may be compromised due to lower perceived ease of use. This study compares subjectively rated usability (N = 37) for three sizes of slanted computer mice and includes a horizontal small conventional device as a reference. For a random subset of the sample (n = 10), objective usability parameters were also elicited. Participants followed a standard protocol which is based on executing graphical pointing, steering, and dragging tasks generated by a purpose-built software. Subjective ratings were collected for each of the four pointing devices tested. The three slanted devices differed in size but were chosen because of an approximately similar slant angle (around 50–60 degrees relative to the horizontal plane). Additionally, effectiveness and efficiency were objectively calculated based on data recorded for the graphical tasks’ software for a random subset of the participants (n = 10). The results unveil small differences in preference in some of the subjective usability parameters across hand size groups. This notwithstanding, the objective efficiency results are aligned with the subjective results, indicating consistency with the hypothesis that smaller slanted devices relative to the user’s hand size are easier to use than larger ones. Mean values of weighted efficiency recorded in the study range from 68% to 75%, with differences across devices coherent with preference rank orders.

Evaluating the Effects of In-Vehicle Side-View Display Layout Design on Physical Demands of Driving

OBJECTIVE

A driving simulator study was conducted to comparatively evaluate the effects of three camera monitor system (CMS) display layouts and the traditional side-view mirror arrangement on the physical demands of driving.

BACKGROUND

Despite the possible benefits of CMS displays in reducing the physical demands of driving, little empirical evidence is available to substantiate these benefits. The effects of CMS display layout designs are not well understood.

METHOD

The three CMS display layouts varied in the locations of the side-view displays: (A) inside the car near the conventional side-view mirrors, (B) on the dashboard at each side of the steering wheel, and (C) on the center fascia with the displays joined side by side. Twenty-two participants performed a safety-critical lane changing task with each design alternative. The dependent measures were the following: spread of eye movement, spread of head movement, and perceived physical demand.

RESULTS

Compared with the traditional mirror system, all three CMS display layouts showed a reduction in physical demands, albeit differing in the types/magnitudes of physical demand reduction.

CONCLUSION

Well-designed CMS display layouts could significantly reduce the physical demands of driving. The physical demands were reduced by placing the CMS displays close to the position of the driver's normal line-of-sight when looking at the road ahead and locating each CMS display on each side of the driver, that is, at locations compatible with the driver's expectation.

APPLICATION

Physical demand reductions by CMS displays would especially benefit drivers frequently checking the side-view mirrors with large eye/head movements and physically weak/impaired drivers.

Comparing learning during the familiarization phase with a slanted mouse and a vertical mouse when performing a repeated pointing-clicking task

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 learning during the familiarization phase. 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.

A tentative efficiency index for pointing device use in computer aided design: A pilot study

BACKGROUND

Focusing on the efficiency aspect of computer pointing devices' usability, this paper reports on a novel and tentative empirically derived efficiency index for 3D CAD.

OBJECTIVE

Three commercially available computer pointing devices were compared: a standard horizontal computer mouse, a vertical device (supporting neutral pronation of the forearm) and a slanted device.

METHODS

Pilot structured observations of 10 subjects' activity were carried out to estimate the proportion of each unique computer mouse operation during CAD modelling with a 3D parametric software. Pointing, dragging and steering standardized tasks were implemented by software and performed by 20 users. Effectiveness and efficiency were calculated and discomfort, effort and ease of use were subjectively assessed.

RESULTS

The mean efficiency index value was lower for the vertical device. Assessments of discomfort, effort and ease of use also supported considering preference for the horizontal and slanted devices, providing limited internal validation.

CONCLUSION

Results suggest the tentative index may offer a valid means of ranking performance of alternative pointing devices regarding operation efficiency.

Assessing ergonomic risks of software: Development of the SEAT

Software utilizing interaction designs that require extensive dragging or clicking of icons may increase users' risks for upper extremity cumulative trauma disorders. The purpose of this research is to develop a Self-report Ergonomic Assessment Tool (SEAT) for assessing the risks of software interaction designs and facilitate mitigation of those risks. A 28-item self-report measure was developed by combining and modifying items from existing industrial ergonomic tools. Data were collected from 166 participants after they completed four different tasks that varied by method of input (touch or keyboard and mouse) and type of task (selecting or typing). Principal component analysis found distinct factors associated with stress (i.e., demands) and strain (i.e., response). Repeated measures analyses of variance showed that participants could discriminate the different strain induced by the input methods and tasks. However, participants' ability to discriminate between the stressors associated with that strain was mixed. Further validation of the SEAT is necessary but these results indicate that the SEAT may be a viable method of assessing ergonomics risks presented by software design.

A literature review of the effects of computer input device design on biomechanical loading and musculoskeletal outcomes during computer work

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.

Evaluating the effect of four different pointing device designs on upper extremity posture and muscle activity during mousing tasks

The goal of this study was to evaluate the effect of different types of computer pointing devices and placements on posture and muscle activity of the hand and arm. A repeated measures laboratory study with 12 adults (6 females, 6 males) was conducted. Participants completed two mouse-intensive tasks while using a conventional mouse, a trackball, a stand-alone touchpad, and a rollermouse. A motion analysis system and an electromyography system monitored right upper extremity postures and muscle activity, respectively. The rollermouse condition was associated with a more neutral hand posture (lower inter-fingertip spread and greater finger flexion) along with significantly lower forearm extensor muscle activity. The touchpad and rollermouse, which were centrally located, were associated with significantly more neutral shoulder postures, reduced ulnar deviation, and lower forearm extensor muscle activities than other types of pointing devices. Users reported the most difficulty using the trackball and touchpad. Rollermouse was not more difficult to use than any other devices. These results show that computer pointing device design and location elicit significantly different postures and forearm muscle activities during use, especially for the hand posture metrics.

Ergonomic Design of a Computer Mouse for Clients With Wrist Splints

OBJECTIVE. We explored effects of cutaneous feedback and hump position on efficiency and comfort in mouse use with a splint. We also analyzed the relationship between anthropometric measurements (width of hand and length of hand, palm, and index) and the task performance.

METHOD. Thirty participants performed a computer task with two forms of mice (front hump and rear hump) and two kinds of wrist splints (dorsal and volar). Movement time and satisfaction scores were recorded.

RESULTS. No interaction effect (Hump Position × Splint Type) was found on movement time. Movement time was shorter for rear-hump mouse users than for front-hump mouse users. Movement time was also shorter for wearers of dorsal wrist splints than for wearers of volar wrist splints. Limited differences existed in the satisfaction scores. Participants with a longer index finger had shorter movement time.

CONCLUSION. Both dorsal wrist splints and rear-hump mice are recommended. Length of index finger positively correlated with task performance.

A biomechanical study of spherical grip

Use of the hand is vital in working life due to the grabbing and pinching it performs. Spherical grip is the most commonly used, due to similarity to the gripping of a computer mouse. Knowledge of its execution and the involved elements is essential. Analysis of this exertion with surface electromyography devices (to register muscular activity) and accelerometer devices (to register movement values ) can provide multiple variables. Six subjects performed ball gripping and registered real-time electromyography (thenar region, hypothenar region, first dorsal interosseous, flexors of the wrist, flexor carpi ulnaris and extensors of the wrist muscles) and accelerometer (thumb, index, middle, ring, pinky and palm) values. The obtained data was resampled "R software" and processed "Matlab Script" based on an automatic numerical sequence recognition program. Electromyography values were normalized on the basis of maximum voluntary contraction, whilst modular values were calculated for the acceleration vector. After processing and analysing the obtained data and signal, it was possible to identify five stages of movement in accordance with the module vector from the palm. The statistical analysis of the variables was descriptive: average and standard deviations. The outcome variables focus on the variations of the modules of the vector (between the maximum and minimum values of each module and phase) and the maximum values of the standardized electromyography of each muscle. Analysis of movement through accelerometer and electromyography variables can give us an insight into the operation of spherical grip. The protocol and treatment data can be used as a system to complement existing assessments in the hand.

Effect of touch screen button size and spacing on touch characteristics of users with and without disabilities

OBJECTIVE

The aim of this study was to investigate the effect of button size and spacing on touch characteristics (forces, impulses, and dwell times) during a digit entry touch screen task. A secondary objective was to investigate the effect of disability on touch characteristics.

BACKGROUND

Touch screens are common in public settings and workplaces. Although research has examined the effect of button size and spacing on performance, the effect on touch characteristics is unknown.

METHOD

A total of 52 participants (n = 23, fine motor control disability; n = 14, gross motor control disability; n = 15, no disability) completed a digit entry task. Button sizes varied from 10 mm to 30 mm, and button spacing was 1 mm or 3 mm.

RESULTS

Touch characteristics were significantly affected by button size. The exerted peak forces increased 17% between the largest and the smallest buttons, whereas impulses decreased 28%. Compared with the fine motor and nondisabled groups, the gross motor group had greater impulses (98% and 167%, respectively) and dwell times (60% and 129%, respectively). Peak forces were similar for all groups.

CONCLUSION

Button size but not spacing influenced touch characteristics during a digit entry task. The gross motor group had significantly greater dwell times and impulses than did the fine motor and nondisabled groups.

APPLICATION

Research on touch characteristics, in conjunction with that on user performance, can be used to guide human computer interface design strategies to improve accessibility of touch screen interfaces. Further research is needed to evaluate the effect of the exerted peak forces and impulses on user performance and fatigue.

Efficient radiologic reading environment by using an open-source macro program as connection software

PURPOSE

The objectives are (1) to introduce an easy open-source macro program as connection software and (2) to illustrate the practical usages in radiologic reading environment by simulating the radiologic reading process.

MATERIALS AND METHODS

The simulation is a set of radiologic reading process to do a practical task in the radiologic reading room. The principal processes are: (1) to view radiologic images on the Picture Archiving and Communicating System (PACS), (2) to connect the HIS/EMR (Hospital Information System/Electronic Medical Record) system, (3) to make an automatic radiologic reporting system, and (4) to record and recall information of interesting cases. This simulation environment was designed by using open-source macro program as connection software.

RESULTS

The simulation performed well on the Window-based PACS workstation. Radiologists practiced the steps of the simulation comfortably by utilizing the macro-powered radiologic environment. This macro program could automate several manual cumbersome steps in the radiologic reading process. This program successfully acts as connection software for the PACS software, EMR/HIS, spreadsheet, and other various input devices in the radiologic reading environment.

CONCLUSION

A user-friendly efficient radiologic reading environment could be established by utilizing open-source macro program as connection software.

Evaluation of technology-assisted learning setups for undertaking assessment and providing intervention to persons with a diagnosis of vegetative state

OBJECTIVE

To evaluate the viability of technology-assisted learning setups for undertaking assessment and providing intervention to persons in vegetative state.

METHOD

Study I investigated whether three persons with a diagnosis of vegetative state could associate eye blinking or hand closure responses with contingent, positive stimulation, thus increasing their frequencies (showing signs of learning). Study II extended the learning process (introducing a new response and new stimuli) for one of the participants of Study I.

RESULTS

Two of the participants of Study I succeeded in increasing their responses, indicating signs of learning. Study II showed that the participant (one of the two succeeding in Study I) acquired a new response to access new stimuli and could alternate this response with the one acquired in Study I.

CONCLUSION

Learning might represent a basic level of knowledge and consciousness. Detecting signs of learning might help modify a previous diagnosis of vegetative state and support intervention/rehabilitation efforts.

A technology-assisted learning setup as assessment supplement for three persons with a diagnosis of post-coma vegetative state and pervasive motor impairment

Post-coma persons in an apparent condition of vegetative state and pervasive motor impairment pose serious problems in terms of assessment and intervention options. A technology-based learning assessment procedure might serve for them as a diagnostic supplement with possible implications for rehabilitation intervention. The learning assessment procedure adopted in this study relied on hand-closure and eye-blinking responses and on microswitch technology to detect such responses and to present stimuli. Three participants were involved in the study. The technology consisted of a touch/pressure sensor fixed on the hand or an optic sensor mounted on an eyeglasses' frame, which were combined with a control system linked to stimulus sources. The study adopted an ABABCB sequence, in which A represented baseline periods, B intervention periods with stimuli contingent on the responses, and C a control condition with stimuli presented non-contingently. Data showed that the level of responding during the B phases was significantly higher than the levels observed during the A phases as well as the C phase for two of the three participants (i.e., indicating clear signs of learning by them). Learning might be deemed to represent basic levels of knowledge/consciousness. Thus, detecting signs of learning might help one revise a previous diagnosis of vegetative state with wide implications for rehabilitation perspectives.

A voice-detecting sensor and a scanning keyboard emulator to support word writing by two boys with extensive motor disabilities

The present study assessed the use of a voice-detecting sensor interfaced with a scanning keyboard emulator to allow two boys with extensive motor disabilities to write. Specifically, the study (a) compared the effects of the voice-detecting sensor with those of a familiar pressure sensor on the boys' writing time, (b) checked which of the sensors the boys preferred, and (c) conducted a social validation assessment of the boys' performance with the two sensors, employing psychology students as raters. The difference in the boys' overall mean writing time per letter across sensors was, by the end of the study, about 1.5s. This difference favored the pressure sensor for one of the boys and the voice-detecting sensor for the other boy. Both boys showed preference for the voice-detecting sensor. Moreover, the psychology students involved in the social validation assessment indicated that such sensor was more satisfactory, suitable, and educationally relevant than the pressure sensor, and represented the solution that they as raters supported more.