A Data-Driven Design Evaluation Tool for Handheld Device Soft Keyboards

Thumb interaction is a primary technique used to operate small handheld devices such as smartphones. Despite the different techniques involved in operating a handheld device compared to a personal computer, the keyboard layouts for both devices are similar. A handheld device keyboard that considers the physical capabilities of the thumb may improve user experience. We developed and applied a design evaluation tool for different geometries of the QWERTY keyboard using a performance evaluation model. The model utilizes previously collected data on thumb motor performance and posture for different tap locations and thumb movement directions. We calculated a performance index (PITOT, 0 is worst and 2 is best) for 663 designs consisting in different combinations of three variables: the keyboard's radius of curvature (R) (mm), orientation (O) (°), and vertical location on the screen (L). The current standard keyboard performed poorly (PITOT = 0.28) compared to other designs considered. Keyboard location (L) contributed to the greatest variability in performance out of the three design variables, suggesting that designers should modify this variable first. Performance was greatest for designs in the middle keyboard location. In addition, having a slightly upward curve (R = −20 mm) and orientated perpendicular to the thumb's long axis (O = −20°) improved performance to PITOT = 1.97. Poorest performances were associated with placement of the keyboard's spacebar in the bottom right corner of the screen (e.g., the worst was for R = 20 mm, O = 40°, L = Bottom (PITOT = 0.09)). While this evaluation tool can be used in the design process as an ergonomic reference to promote user motor performance, other design variables such as visual access and usability still remain unexplored

Tablet Keyboard Configuration Affects Performance, Discomfort and Task Difficulty for Thumb Typing in a Two-Handed Grip

When holding a tablet computer with two hands, the touch keyboard configuration imposes postural constraints on the user because of the need to simultaneously hold the device and type with the thumbs. Designers have provided users with several possible keyboard configurations (device orientation, keyboard layout and location). However, potential differences in performance, usability and postures among these configurations have not been explored. We hypothesize that (1) the narrower standard keyboard layout in the portrait orientation leads to lower self-reported discomfort and less reach than the landscape orientation; (2) a split keyboard layout results in better overall outcomes compared to the standard layout; and (3) the conventional bottom keyboard location leads to the best outcomes overall compared to other locations. A repeated measures laboratory experiment of 12 tablet owners measured typing speed, discomfort, task difficulty, and thumb/wrist joint postures using an active marker system during typing tasks for different combinations of device orientation (portrait and landscape), keyboard layout (standard and split), and keyboard location (bottom, middle, top). The narrower standard keyboard with the device in the portrait orientation was associated with less discomfort (least squares mean (and S.E.) 2.9±0.6) than the landscape orientation (4.5±0.7). Additionally, the split keyboard decreased the amount of reaching required by the thumb in the landscape orientation as defined by a reduced range of motion and less MCP extension, which may have led to reduced discomfort (2.7±0.6) compared to the standard layout (4.5±0.7). However, typing speed was greater for the standard layout (127±5 char./min.) compared to the split layout (113±4 char./min.) regardless of device orientation and keyboard location. Usage guidelines and designers can incorporate these findings to optimize keyboard design parameters and form factors that promote user performance and usability for thumb interaction

A Randomized Controlled Trial of a Truck Seat Intervention: Part 2-Associations Between Whole-Body Vibration Exposures and Health Outcomes

This randomized controlled trial study was conducted to determine whether two different seating interventions would reduce exposure to whole-body vibration (WBV) and improve associated health outcomes. Forty professional truck drivers were randomly assigned to two groups: (i) a control group of 20 drivers who received a new, industry-standard air-suspension seat, and (ii) an intervention group of 20 drivers who received an active-suspension seat. This study collected regional body pain (10-point scale), low back disability [Oswestry Disability Index (OD1)], physical and mental health [the Short Form 12-item Health Survey (SF-12)], and work limitations [Work Limitation Questionnaire (WLQ)] before and 3, 6, and 12 months after the seating intervention. WBV exposures were also collected during the same time periods. Due to dropouts at the 12-month time period, only data up to 6 months post-intervention were included in the analyses. The post-intervention A(8) WBV exposures were lower in both groups with a more substantial WBV exposure reduction (similar to 50%) in the intervention group compared to the control group (similar to 26%). There was little to no change in the impulsive exposures [VDV(8) and S-ed(8)] post-intervention and no differences between the two groups. The self-reported musculoskeletal health outcomes showed that intervention group experienced a greater reduction in the low back pain (LBP) and other musculoskeletal outcomes than the control group. The LBP reduction in the intervention group was clinically meaningful (>25%); however, none of the changes in pain reached statistical significance (P's > 0.22).The SF-12 health scores demonstrated that the intervention group's physical health improved after the intervention (P's 0.11).The WLQ scores showed that the intervention group generally experienced reduced (improved) work limitation over time whereas the control group showed inconsistent changes in work limitation scores.These study findings indicate that reducing truck drivers' exposure to WBV through seating intervention can lead to improvements in LBP and other health outcomes

A Randomized Controlled Trial of a Truck Seat Intervention: Part 1-Assessment of Whole Body Vibration Exposures

Full-time vehicle and heavy equipment operators often have a high prevalence of musculoskeletal disorders, especially low back pain (LBP). In occupations requiring vehicles or heavy equipment operation, exposure to whole body vibration (WBV) has been consistently associated with LBP. LBP is the most common cause of work-related disability and continues to be the leading cause of morbidity and lost productivity in the US workforce. Using a parallel randomized controlled trial design, over a 12-month period, this study evaluated two different seating interventions designed to reduce WBV exposures. Forty professional truck drivers were initially recruited and randomly assigned to one of two groups: (I) a passive suspension/control group-20 drivers who received a new, industry-standard air-suspension seat, and (ii) an intervention group-20 drivers who received an active-suspension seat, which has been shown to reduce vertical WBV exposures by up to 50% compared to passive seats. WBV exposures from the truck seat and floor were collected during driver's full shifts (6-18 h) before (pre-intervention) and after the intervention (0, 3, 6, and 12 months post-intervention) per International Standards Organization (ISO) 2631-1 and 2631-5WBV standards. After subject dropout and turnover, 16 truck drivers remained in each group. The pre-intervention WBV data showed that there were no differences in the daily equivalent time-weighted average WBV exposures (A(8)], vibration dose values [VDV(8)], and static spinal compression doses [S-ed(8)] between the two groups (P's > 0.36). After the new seats were installed, the A(8) values showed that the active suspension/ intervention group experienced much greater reduction in the vertical (z) axis[(similar to 50%; P= <0.0001; Cohen's d effect size (95% CI) = 1.80 (1.12, 2.48)] exposures when compared to in the passive suspension/control group [similar to 20%; P = 0.23; 0.33 (-0.36, 1.02)].The post-intervention z-axis VDV(8) and S-ed(8) WBV exposure measures were not different between the two seat groups [VDV(8), P. 0.33; 0.35 (-0.32, 1.03); S-ed(8), P. 0.61; 0.08 (-0.59, 0.76)].These study findings indicate that, relative to the current industry-standard, passive air-suspension seats which are ubiquitous in all semi-trucks today, the active suspension seat dramatically reduced average continuous [A(8)] WBV exposures but not periodic, cumulative impulsive exposures [VDV(8) and S-ed(8)]

Prediction of trapezius muscle activity and shoulder, head, neck, and torso postures during computer use: results of a field study

Background: Due to difficulties in performing direct measurements as an exposure assessment technique, evidence supporting an association between physical exposures such as neck and shoulder muscle activities and postures and musculoskeletal disorders during computer use is limited. Alternative exposure assessment techniques are needed. Methods: We predicted the median and range of amplitude (90th-10th percentiles) of trapezius muscle activity and the median and range of motion (90th-10th percentiles) of shoulder, head, neck, and torso postures based on two sets of parameters: the distribution of keyboard/mouse/idle activities only (“task-based” predictions), and a comprehensive set of task, questionnaire, workstation, and anthropometric parameters (“expanded model” predictions). We compared the task-based and expanded model predictions based on R2 values, root mean squared (RMS) errors, and relative RMS errors calculated compared to direct measurements. Results: The expanded model predictions of the median and range of amplitude of trapezius muscle activity had consistently better R2 values (range 0.40-0.55 compared to 0.00-0.06), RMS errors (range 2-3%MVC compared to 3-4%MVC), and relative RMS errors (range 10-14%MVC compared to 16-19%MVC) than the task-based predictions. The expanded model predictions of the median and range of amplitude of postures also had consistently better R2 values (range 0.22-0.58 compared to 0.00-0.35), RMS errors (range 2–14 degrees compared to 3–22 degrees), and relative RMS errors (range 9–21 degrees compared to 13–42 degrees) than the task-based predictions. Conclusions: The variation in physical exposures across users performing the same task is large, especially in comparison to the variation across tasks. Thus, expanded model predictions of physical exposures during computer use should be used rather than task-based predictions to improve exposure assessment for future epidemiological studies. Clinically, this finding also indicates that computer users will have differences in their physical exposures even when performing the same tasks

Gestural Workspaces for Computer Interaction, Configuration and Performance

While the hardware challenges facing integration of hand-gestural controls into mainstream computer interfaces appear to be shrinking, design challenges related to the physical and mental burden required of gesture interfaces remain. This study aims to determine the effect of the gestural workspace configuration (vertical, horizontal, and jointspace) and affordance of arm support on speed, accuracy, and performance when performing pointing tasks on a computer. Seventeen participants played a computer card game (Solitaire) and then completed Fitts’ serial clicking tasks to evaluate performance in five gestural workspace configurations implemented using a Microsoft Kinect®. Gestural input configurations were also compared to a traditional mouse input. A traditional mouse performed better than gestural controls in all aspects of performance. Among gestural workspaces, the vertical configuration performed significantly better in throughput and accuracy outcomes. Limitations of the gestural tracking system and large variation in individual performance may hinder establishment of generalized design recommendations at this point; however, gestural workspace configurations with direct mapping to onscreen movements and the presence of supporting surfaces appear to increase user performance and reduce perceived difficulty

Effects of forearm and palm supports on the upper extremity during computer mouse use

The use of forearm and palm supports has been associated with lower neck and shoulder muscle activity as well as reduced musculoskeletal discomfort during keyboard use, however, few studies have investigated their effect during computer mouse use. Eight men and eight women completed several computer mousing tasks in six arm support conditions: Forearm Support, Flat Palm Support, Raised Palm Support, Forearm + Flat Palm Support, Forearm + Raised Palm Support, and No Support. Concurrently, an infrared three-dimensional motion analysis system measured postures, six-degree-of-freedom force-torque sensors measured applied forces & torques, and surface electromyography measured muscle activity. The use of forearm support compared to the no support condition was significantly associated with less shoulder muscle activity & torque, and the raised palm support was associated with less wrist extension. Forearm supports reduced shoulder flexion torque by 90% compared to no support. The use of either support also resulted in lower applied forces to the mouse pad. Participants reported less musculoskeletal discomfort when using a support. These results provide recommendations for office workstation setup and inform ergonomists of effective ways to reduce musculoskeletal exposures