Observed finger behaviour during computer mouse use

Impact of repetitive mouse clicking on forearm muscle fatigue and mouse aiming performance

Exercise induced performance fatigue has been shown to impair many aspects of fine motor function in the distal upper limb. However, most fatiguing protocols do not reflect the conditions experienced with computer use. The purpose of this study was to determine how a prolonged, low-force mouse clicking fatigue protocol impacts performance fatigue of the distal upper limb for gamers and non-gamers. Participants completed a total of 1 h of mouse clicking at 5 clicks per second. Muscle fatigue and performance were intermittently assessed. RMS amplitude increased for the forearm flexors throughout the fatigue protocol. Accuracy decreased following the first bout of clicking and returned to baseline values after 40-min. EDC and ECU displayed the greatest muscle activity while aiming, producing 11.4% and 12.9% of MVC, respectively. These findings indicate that mouse clicking may not result in performance fatigue, however, high levels of extensor activity may explain common injuries among gamers.

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.

Mouse with your arm™: Facilitating forearm support using the chair armrest to prevent and mitigate musculoskeletal disorders

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.

An Investigation on the Sampling Frequency of the Upper-Limb Force Myographic Signals

Force myography (FMG) is an emerging method to register muscle activity of a limb using force sensors for human-machine interface and movement monitoring applications. Despite its newly gained popularity among researchers, many of its fundamental characteristics remain to be investigated. The aim of this study is to identify the minimum sampling frequency needed for recording upper-limb FMG signals without sacrificing signal integrity. Twelve healthy volunteers participated in an experiment in which they were instructed to perform rapid hand actions with FMG signals being recorded from the wrist and the bulk region of the forearm. The FMG signals were sampled at 1 kHz with a 16-bit resolution data acquisition device. We downsampled the signals with frequencies ranging from 1 Hz to 500 Hz to examine the discrepancies between the original signals and the downsampled ones. Based on the results, we suggest that FMG signals from the forearm and wrist should be collected with minimum sampling frequencies of 54 Hz and 58 Hz for deciphering isometric actions, and 70 Hz and 84 Hz for deciphering dynamic actions. This fundamental work provides insight into minimum requirements for sampling FMG signals such that the data content of such signals is not compromised.

Assessment of functional parameters and comfort of a new computer mouse as compared with other types of input devices

BACKGROUND

This study was conducted to assess functional parameters and comfort of a new computer mouse (Ergomice) as compared with three other input devices.

MATERIALS AND METHODS

Functional parameters (i.e., task completion time and error rate) of each device were assessed by 10 participants using standardized software based on Standard No. ISO 9241-9:2000. Comfort evaluation was also undertaken for each device using the visual analogue scale technique. Statistical analysis including the Wilcoxon signed-rank test and the Friedman test was performed using SPSS version 16.

RESULTS

The functional parameters of the standard mouse were better than those of the other devices. However, no significant difference was observed between this mouse and Ergomice. Overall comfort evaluation showed that the standard mouse and Ergomice were more comfortable to work with. The comfort level of hand/wrist posture in the Ergomice was higher than that of the other three devices.

CONCLUSION

The design features of Ergomice could improve its functional properties. Hand/wrist posture comfort of Ergomice was judged to be high compared with that of the other devices.

The position of a standard optical computer mouse affects cardiorespiratory responses during the operation of a computer under time constraints

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.

Effects of slanted ergonomic mice on task performance and subjective responses

The biomechanical benefits (e.g., muscular activity) of slanted ergonomic mice have been comprehensively identified; however, their effects on task performance and subjective responses have not been fully investigated. The present study examined the effects of two slanted mice (slant angle = 30° and 50°) in comparison with a conventional mouse (slant angle = 0°) in terms of task performance (task completion time and error rate) and subjective responses (perceived discomfort score and overall satisfaction score). Experimental results showed that all of the task and subjective measures worsened as the slant angle of the target mice increases. For example, the task completion time (unit: ms) and overall satisfaction score (unit: point) of the 30° slanted mouse (time = 0.71, satisfaction = -0.09) and 50° slanted mouse (time = 0.73, satisfaction = -0.79) significantly deteriorated than the conventional mouse (time = 0.65, satisfaction = 1.21). The slanted mice seem to compromise biomechanical benefits with task performance and subjective responses.

Contact pressure in the wrist during computer mouse work

This study investigated the relationship between computer mouse work and contact pressure around the pisiform. Commonly performed mouse work was simulated using 3 different-shaped mice with 3 forearm positions. When typical mouse work was performed, the contact pressure on the pisiform area was evaluated using a digital pressure sensor and compared with that of the thenar area. Six mouse tasks were simulated. Results indicate that mouse users should avoid wrist-snap dragging and resting their wrist on the edge of the desk to minimize the pressure concentration on the pisiform area.

Design and validation of an improved graphical user interface with the 'Tool ball'

The purpose of this research is introduce the design of an improved graphical user interface (GUI) and verifies the operational efficiency of the proposed interface. Until now, clicking the toolbar with the mouse is the usual way to operate software functions. In our research, we designed an improved graphical user interface - a tool ball that is operated by a mouse wheel to perform software functions. Several experiments are conducted to measure the time needed to operate certain software functions with the traditional combination of "mouse click + tool button" and the proposed integration of "mouse wheel + tool ball". The results indicate that the tool ball design can accelerate the speed of operating software functions, decrease the number of icons on the screen, and enlarge the applications of the mouse wheel.

A wide range of activity duration cutoffs provided unbiased estimates of exposure to computer use

Integrative computer usage monitors have become widely used in epidemiologic studies to investigate the exposure-response relationship of computer-related musculoskeletal disorders. These software programs typically estimate the exposure duration of computer use by summing precisely recorded durations of input device activities and durations of inactivity periods shorter than a predetermined activity duration cutoff value, usually 30 or 60 sec. The goal of this study was to systematically compare the validity of a wide range of cutoff values. Computer use activity of 20 office workers was observed for 4 consecutive hours using both a video camera and a usage monitor. Video recordings from the camera were analyzed using specific observational criteria to determine computer use duration. This observed duration then served as the reference and was compared with 238 estimates of computer use duration calculated from the usage monitor data using activity duration cutoffs ranging from 3 to 240 sec in 1-sec increments. Estimates calculated with cutoffs ranging from 28 to 60 sec were highly correlated with the observed duration (Spearman's correlation 0.87 to 0.92) and had nearly ideal linear relationships with the observed duration (slopes and r-squares close to one, and intercepts close to zero). For the same range of cutoff values, when the observed and estimated durations were compared for dichotomous exposure classification across participants, minimal exposure misclassification was observed. It is concluded that activity duration cutoffs ranging from 28 to 60 sec provided unbiased estimates of computer use duration.