Lovenoor Aulck

The Effect of Key Size of Touch Screen Virtual Keyboards on Productivity, Usability, and Typing Biomechanics

Objective: We investigated whether different virtual keyboard key sizes affected typing force exposures, muscle activity, wrist posture, comfort, and typing productivity. Background: Virtual keyboard use is increasing and the physical exposures associated with virtual keyboard key sizes are not well documented. Method: Typing forces, forearm/shoulder muscle activity, wrist posture, subjective comfort, and typing productivity were measured from 21 subjects while they were typing on four different virtual keyboards with square key sizes, which were 13, 16, 19, and 22 mm on each side with 2-mm between-key spacing. Results: The results showed that virtual keyboard key size had little effect on typing force, forearm muscle activity, and ulnar/radial deviation. However, the virtual keyboard with the 13-mm keys had a 15% slower typing speed (p < .0001), slightly higher static (10th percentile) shoulder muscle activity (2% maximum voluntary contractions, p = .01), slightly greater wrist extension in both hands (2° to 3°, p < .01), and the lowest subjective comfort and preference ratings (p < .1). Conclusions: The study findings indicate that virtual keyboards with a key size less than 16 mm may be too small for touch typing given the slower typing speed, higher static shoulder muscle activity, greater wrist extension, and lowest subjective preferences. Applications: We evaluated the effects of virtual keyboard key sizes on typing force exposures, muscle activity, comfort, and typing productivity.

Are there Differences in Force Exposures and Typing Productivity between Touchscreen and Conventional Keyboard

As the use of tablets is becoming increasingly prevalent, it is important to understand how using a touchscreen (virtual) keyboard affects typing forces, productivity and comfort. Thus, the objective of this study was to investigate whether there were differences in typing forces, typing productivity and users’ discomfort between virtual and conventional keyboards. A total of 19 subjects (10 males and 9 females) typed for 10 minutes on a virtual keyboard and two conventional keyboards. The results showed that virtual keyboard use resulted in lower typing forces (p < 0.0001), lower typing performance (p < 0.0001), and higher subjective discomfort at the hand/wrist and the neck/shoulder (p < 0.0001). The results indicate that using a virtual keyboard may not cause any detrimental effect on physical exposures, but may increase musculoskeletal discomfort on the upper extremities and neck/shoulder regions; therefore, appropriate interventions should be considered for the prolonged use of a virtual keyboard.

Whole Body Vibration Exposures and Health Status among Professional Truck Drivers: A Cross-sectional Analysis

Many professional truck drivers suffer from low back pain (LBP) which is thought to be associated with exposure to whole-body vibration (WBV). The objectives of this study were to: (i) characterize general health, regional body pain and WBV exposures, (ii) evaluate the associations between different WBV parameters and health outcomes, and (iii) determine whether there were factors which affect a truck drivers WBV exposures. This study analyzed WBV exposures from 96 long-haul truck drivers over their regular work shift (6-15h) per International Standards Organization (ISO) 2631-1 and 2631-5 WBV standards. This study also evaluated regional body pain (10-point scale), low back disability (the Oswestry Disability Index), and physical and mental health (the Short Form 12-item Health Survey). The results demonstrated that the daily vector sum WBV exposures [A(8), VDV(8) and Sed(8)] were above action limits while the predominant z-axis exposures were below action limits. Among all the musculoskeletal outcomes, LBP was the most prevalent (72.5%) with average LBP score of 2.9 (SD: 2.0). The SF-12 health scores demonstrated that truck drivers in general had lower physical health status than the general US population (Ps < 0.04) and that physical health status decreased as WBV exposures increased (P = 0.03). In addition, the correlations between the WBV measures and health outcomes indicated that A(8) exposure measures had a stronger link to musculoskeletal (LBP) and other health outcomes than the VDV(8) and Sed(8) measures. Finally, seat manufacturer and seat age were two factors which had a strong influence on WBV exposures.

The effects of touch screen virtual keyboard key sizes on typing performance, typing biomechanics and muscle activity

The goal of the present study was to determine whether different touch screen virtual keyboard key sizes affected typing productivity, typing forces, and muscle activity. In a repeated-measures laboratory experiment with 21 subjects, typing speed, accuracy, muscle activity, and typing forces were measured and compared between four different key sizes: 13x13, 16x16, 19x19, and 22x22 mm. The results showed that 13 mm keyboard had a 15% slower typing speed (p < 0.0001) and slightly higher static (10th %tile) shoulder muscle activity (2%, p = 0.01) as compared to the other keyboards with larger keys. The slower typing speed and slightly higher shoulder muscle activity indicated that 13 mm keyboard may be less optimal for touch typing compared to the larger key sizes.

Whole Body Vibration Exposures in Long-haul Truck Drivers:

Many professional truck drivers experience low back pain (LBP) which is believed to be associated with exposure to whole body vibration (WBV). As a part of a randomized controlled trial, this study measured WBV exposures from 98 professional truck drivers continuously during their regular work shift (8-12 hours). The daily weighted average A(8), vibration dose value VDV(8), and vector sum A(8) and VDV(8) exposures were evaluated for important determinants of WBV exposures including the roads travelled on, year of truck manufacture, truck manufacturer, and seat manufacturer. LBP was also measured using a standardized visual analog scale. The results demonstrated that there were substantial differences in health risk prediction between the predominant axis exposure (advocated by the European Union Vibration Directives) and vector sum exposures. Moreover, VDV(8) measures were above the International Organization for Standardization and European Union daily exposure action limit (9.1 m/s2). The average LBP score on a 0 to 10 point scale was 2.7 (SD: 2.0) ranging from 0 to 8. When comparing the two major manufacturers of truck seats, one truck seat had higher vertical, z-axis A(8) exposures than the other (24%, p =0.01); and this WBV exposure difference appeared to be reflected by the LBP outcomes. These results indicate that there are performance differences between seats in the attenuation of WBV exposures and truck drivers’ impulsive WBV exposure can exceed recommended daily action limits.

The Effects of Virtual Keyboard Key Sizes on Typing Productivity and Physical Exposures

With mobile devices including tablet PCs, gravitating towards smaller sizes, the keyboard key sizes on these devices often have to be smaller than recommended key sizes and spacing (18 to 20 mm) for notebook and desktop keyboards. Currently, there is limited research into how key sizes can affect typing proficiency and physical exposures during virtual keyboard use. Therefore, the present study investigated how different virtual keyboard key sizes affected muscle activity, wrist posture, and typing productivity. A total of 21 subjects (12 males and 9 females) participated in a repeated-measures laboratory experiment where typing speed, accuracy, muscle activity, wrist posture, and subjective discomfort were compared between four different virtual keyboards with key sizes (width x height) of 13x13, 16x16, 19x19, and 22x22 mm with a 2-mm gutter surrounding each key. The results showed that the keyboard with the 13x13 mm keys (15 mm center-to-center key spacing) had a 15% slower typing speed (p < 0.0001), higher static (10th %tile) shoulder muscle activity (2% MVC, p = 0.01), and greater wrist extension in both hands (2° - 3°, p’s < 0.01). The study findings indicate that 13x13 mm key size may not be optimal for touch typing on a virtual keyboard.

Attrition and performance of community college transfers.

Community colleges are an important part of the US higher education landscape, yet the aptitude and preparedness of student transfers to baccalaureate institutions is often called into question. Examining transcript records and demographic information of nearly 70,000 students across over 15 years of registrar records at a public university, this study performed a descriptive analysis of the persistence, performance, and academic migration patterns of community college transfers, transfers from four-year institutions, and freshmen entrants. We found little difference between community college transfers and freshmen entrants in terms of post-transfer grades and persistence. Transfers from four-year institutions had higher grades but also had higher attrition rates than their peers. This study also found no strong evidence of transfer shock on students’ post-transfer grades. When examining the tendencies of students to shift fields of study during their educational pursuits, the academic migration patterns of transfer students were more concentrated than those of freshmen entrants.

The effects of work surface hardness on mechanical stress, muscle activity, and wrist postures

BACKGROUND Contact pressure is a risk factor which can contribute to musculoskeletal disorders. OBJECTIVE The objective of the present study was to determine whether a work surface with a soft, pliable front edge could reduce contact pressure, muscle activity, and subjective musculoskeletal comfort, and improve wrist posture relative to a conventional, hard work surface. METHODS In a repeated-measures blinded experiment with eighteen subjects (8 females and 10 males), contact pressure, wrist posture, typing productivity, perceived fatigue, wrist and shoulder muscle activity, and subjective comfort were compared between the two different work surfaces during keyboard use, mouse use and mixed mouse and keyboard use. RESULTS The results showed that across the three modes of computer work, the contact pressure was lower on the soft-edge work surface compared to the conventional work surface (ps <0.03) and subjects reported to have less perceived fatigue in the forearms and wrists. No differences in muscle activity, wrist posture, and subjective comfort were measured between the two work surfaces. CONCLUSIONS Given the significant reduction in contact pressure and corresponding lower ratings in perceived fatigue, the soft-edge work surface subjectively and objectively improved measures of contact stress which may reduce physical exposures associated with the onset and development of musculoskeletal disorders.

Comparison of Exposure to Repetitive Upper Arm Motions and Non-neutral Upper Arm Postures between Apple Harvesting with Ladders and Mobile Platforms

In attempts to improve productivity in agriculture, a harvest-assisting mobile platform has been developed and is being evaluated for use in Washington State apple orchards; however, its ergonomic effect on work postures and repetitive motions has not yet been characterized. The purposes of this study were: 1) to compare physical exposures between two methods of apple harvesting: a conventional ladder and a newly-developed mobile platform, and 2) to develop systematic methods for characterizing work repetitions, specifically in the upper arms. Using self-contained tri-axial inclinometers with built-in memory, upper arm inclinations were continuously monitored from twenty male workers over a full day of apple harvesting. At the beginning and the end of work shift, Borg CR10 scales were used as self-report measures of perceived fatigue in the shoulder. Postural exposures were characterized as the percent of time the upper arm postures exceeded specified angle ranges. Repetition was evaluated using changes in upper arm angles ranging from 5 to 30 degrees. In terms of prolonged postural exposures, repetitive work exposure and perceived fatigue in the shoulders, the workers using the mobile platform had less physical stress compared to the workers using the ladders. In addition, the upper arm repetition rates were high (over 15 repetitions per minute) for both harvesting methods. A more systematic study of the harvesting methods is needed to characterize differences in repetition rates and productivity between the mobile platforms and ladders. However, the results indicate that the mobile platform could improve workability and may enable more diverse workers to participate in harvesting activities.

Evaluation of Contact Pressure and Biomechanical Exposures on Different Work Surface Hardness

Contact pressure has been identified as a risk factor for musculoskeletal disorders (MSDs) in various occupational settings. Given that contact pressure over the palmar aspect of the wrists may increase risks for MSDs, the present study was designed to determine whether a work surface with a soft leading edge could reduce contact pressure and subjective musculoskeletal discomfort without affecting task performance during a series of standardized computer work tasks. Using a repeated-measures blinded experimental design with eighteen subjects, during the performance of a series of standardized computer work tasks, contact pressure, computer work performance and perceived fatigue in the upper extremities were evaluated and compared between a conventional hard-edge and soft-edge work surface. The results found that contact pressure and perceived fatigue in the wrists were lower on the soft-edge work surface compared to the conventional hard-edged work surface (p’s < 0.03), whereas no differences were found in computer task performance between the two work surfaces. The study findings showed that soft-edge work surface reduced contact pressure in the wrists and the reduction in contact stress may reduce the risks for developing work-related MSDs when working at the computer.