Effects of button position on a soft keyboard: Muscle activity, touch time, and discomfort in two-thumb text entry

Ergonomic evaluation of upper extremities muscle activity pattern during 60-min smartphone texting

BACKGROUND

Smartphone usage has increased rapidly in the last decade due to rapid technological advancements. This extensive usage of smartphones led to physiological problems and musculoskeletal disorders (MSD) due to inappropriate postures.

OBJECTIVE

Past studies have reported the effects/discomfort of smartphone usage for short periods, ranging from 3-20 min, which does not represent the current era of smartphone dependency (approximately 7-hr/day).

METHODS

This study was performed on fifty-four participants aged 20-28 with 1-hr smartphone texting in a sitting posture. Flexion angles, both sides (dominant and non-dominant) muscle activity (maximum voluntary contraction %) at sternocleidomastoid (SCM), upper-trapezius (TRP), extensor digitorum (EDM) and abductor pollicis brevis (APB) muscles, and subjective discomfort were analyzed.

RESULTS

After 1-hr smartphone texting, the muscle activity at eight upper extremities: SCM (24.80%), TRP (29.45%), EDM (14.44%) and APB (19.87%) significantly (p < 0.001) increased by 1.5-1.9 times with 27.4±3.18° and 82.94±7.03° head and lower-arm flexion angles, respectively. The mechanical loads on the cervical spine increased by 4.6 times, and subjective discomfort by 3 times.

CONCLUSION

Maintaining the same posture for a long duration causes postural stress, muscular imbalances, and discomfort, leading to MSD with increased cervical intervertebral disc pressure.

Usability of curved keyboard design on the large smartphone: An empirical study

The curved design is ubiquitous, with a vast user base due to its similarity with in shape to human physiological structure. The curved QWERTY keyboard layout was proposed for one-handed usage on smartphones with ambiguous effects. This study evaluated whether the curved QWERTY could optimize the user experience and input performance on large smartphones better than the traditional straight QWERTY layout. Eight measurements were used to evaluate the usability of each design, six suggesting curved QWERTY failed to achieve outstanding typing performance or subjective user experience, while the other two indicators showed that curved QWERTY had advantages in touch dispersion and touching offset, indicating the possible higher usability it could reach. The results also investigated the potential application of curved designs and provided insights into the optimization methods.

Alterations in Physical Demands During Virtual/Augmented Reality-Based Tasks: A Systematic Review

The digital world has recently experienced a swift rise in worldwide popularity due to Virtual (VR) and Augmented Reality (AR) devices. However, concrete evidence about the effects of VR/AR devices on the physical workload imposed on the human body is lacking. We reviewed 27 articles that evaluated the physical impact of VR/AR-based tasks on the users using biomechanical sensing equipment and subjective tools. Findings revealed that movement and muscle demands (neck and shoulder) varied in seven and five studies while using VR, while in four and three studies during AR use, respectively, compared to traditional methods. User discomfort was also found in seven VR and three AR studies. Outcomes indicate that interface and interaction design, precisely target locations (gestures, viewing), design of virtual elements, and device type (location of CG as in Head-Mounted Displays) influence these alterations in neck and shoulder regions. Recommendations based on the review include developing comfortable reach envelopes for gestures, improving wearability, and studying temporal effects of repetitive movements (such as effects on fatigue and stability). Finally, a guideline is provided to assist researchers in conducting effective evaluations. The presented findings from this review could benefit designers/evaluations working towards developing more effective VR/AR products.

Assessment of the Effect of Smartphone Usage on the Range of Motion and Fatigability of the Joints and Muscles of the Thumb Among Users: A Cross-Sectional Study in Central India

Introduction

The ability of adaptation is unique to humankind. Technology advances have introduced many appliances that increasingly are smaller in size and handheld. These devices on prolonged usage affect the thumb joint complex, and this study was therefore designed to assess any changes in the movement of the thumb joint complex and fatigability secondary to the increasing usage of smartphones in different orientations in the Central Indian population.

Materials and methods

An analytical cross-sectional study was performed to assess changes in the ranges of motion (ROM) of the thumb joint complex with a sample size of 137 selected nonrandomly and categorized on the basis of the orientation of smartphone usage by physical goniometer and a standardized questionnaire to assess fatigability.

Results

Most movements of the thumb joint complex corresponded to the existing standard values. The study found significant changes in the movement of passive flexion of the left metacarpophalangeal (MCP) joint and borderline significant modifications in the active extension of the left interphalangeal (IP) joint, passive extension of the left interphalangeal joint, and passive flexion of the left carpometacarpal (CMC) joint among the groups of participants. The Borg CR10 value of fatigue was “one,” indicative of no excessive fatigue after smartphone usage.

Conclusion

There are no significant changes in the ranges of motion of the joint complex of the thumb in mobile phone users over a period of time. The orientations and the increased duration of usage also did not cause any fatigue in the muscles of the thumb.

Repetitive patterns in the locations of touch errors for two-thumb text entry on a smartphone

This study investigated repetitive patterns in the locations of touch errors as a function of the shapes and positions of soft buttons on a smartphone for two-thumb text entry. Forty-three right-handed college students with smartphone-use experience were recruited for testing. An experimental application was developed, and the locations and frequencies of touch errors were measured for the button combinations of seven shapes and eight positions. More than 70.0 % of touch errors occurred within 2 mm from the boundaries of the buttons. In terms of direction, touch errors were primarily observed below the buttons, across all the button shapes and positions. Simultaneously, touch errors often appeared on the lateral sides of the buttons: (1) close to the proximal phalange of the thumbs when the buttons were placed near the initial positions of the thumbs and (2) close to the initial positions of the thumbs when the buttons were placed near the top and bottom ends of the keyboard.

Analysis of natural finger-press motions for design of trackball buttons

This study analysed natural press motions of the index, middle and ring fingers for ergonomic design of the positions and surface angles of the left, middle and right trackball buttons. Finger motions of 26 male participants for naturally pressing the trackball buttons were recorded after the participants adjusted the trackball buttons to their preferred locations for comfortable pressing. The natural positions of the finger pulps formed a symmetrically rainbow-shaped reach zone for the fingers. The natural press angles of the fingers' motion trajectories to the vertical reference line ranged from 14.2° to 20.5°, suggesting an 18-degree surface from the horizontal line for the trackball buttons. Regression formulas (adjusted R² = 0.90 ± 0.07 and mean squared error = 8.55 ± 7.52 mm) were established to estimate the natural positions of finger pulps from hand segment lengths and joint angles for a population having different hand sizes from this study. Relevance to industry.

Development of a press and drag method for hyperlink selection on smartphones

The present study developed a novel touch method for hyperlink selection on smartphones consisting of two sequential finger interactions: press and drag motions. The novel method requires a user to press a target hyperlink, and if a touch error occurs he/she can immediately correct the touch error by dragging the finger without releasing it in the middle. The method was compared with two existing methods in terms of completion time, error rate, and subjective rating. Forty college students participated in the experiments with different hyperlink sizes (4-pt, 6-pt, 8-pt, and 10-pt) on a touch-screen device. When hyperlink size was small (4-pt and 6-pt), the novel method (time: 826 msec; error: 0.6%) demonstrated better completion time and error rate than the current method (time: 1194 msec; error: 22%). In addition, the novel method (1.15, slightly satisfied, in 7-pt bipolar scale) had significantly higher satisfaction scores than the two existing methods (0.06, neutral).