Wrist and shoulder posture and muscle activity during touch-screen tablet use: Effects of usage configuration, tablet type, and interacting hand

Effect of tablet tilt positioning on ergonomic risks and respiratory function

The static posture associated with continuous tablet use can lead to musculoskeletal disorders of the neck and upper extremities as well as respiratory function disorders. We hypothesized that 0-degree tablet placement (flat on a table) would affect ergonomic risks and respiratory function. Eighteen undergraduate students were divided into two groups (n = 9 per group). In the first group, the tablet was placed at a 0-degree angle, whereas in the second group, it was placed at a 40- to 55-degree angle on a student learning chair. The tablet was used continuously for 2 h for writing and internet use. Rapid upper-limb assessment (RULA), craniovertebral angle, and respiratory function were assessed. There was no significant difference in respiratory function, including forced expiratory volume in 1 s (FEV₁), forced vital capacity (FVC), and FEV₁/FVC, between the groups (p = 0.09) or within groups. However, there was a statistically significant between-group difference in RULA (p = 0.001), with the 0-degree group having a greater ergonomic risk. There were also significant within-group differences between pre- and posttest. The CV angle differed significantly between groups (p = 0.03), whereby the 0-degree group had poor posture, as well as within the 0-degree group (p = 0.039), though not within the 40- to 55-degree group (p = 0.067). Undergraduate students who place their tablets at a 0-degree angle face increased ergonomic risks and higher potential for developing musculoskeletal disorders and poor posture. Thus, elevating the tablet and instituting rest intervals may prevent or decrease the ergonomic risks among tablet users.

Computer Vision Syndrome: An Ophthalmic Pathology of the Modern Era

Digital device usage has increased significantly in last decade among all age groups, both for educational and recreational purposes. Computer vision syndrome (CVS), also known as digital eye strain (DES), represents a range of ocular, musculoskeletal, and behavioral conditions caused by prolonged use of devices with digital screens. This paper reviews the principal environmental, ocular, and musculoskeletal causes for this condition. Due to the high prevalence of DES and frequent usage of digital devices, it is important that eye care practitioners be able to provide advice and management options based on quality research evidence.

The effect of tablet tilt angles and time on posture, muscle activity, and discomfort at the neck and shoulder in healthy young adults

BACKGROUND

Although young adults regularly perform tablet writing, biomechanics during the tablet writing with different tilt angles has not been studied. The objective of this study was to compare posture, muscle activity, and discomfort at the neck and shoulder between tablet writing with 0° (horizontal) and 30° tablet tilt angles over 40 minutes in healthy young adults.

METHODS

Twenty participants wrote continuously for 40 minutes on a tablet with both tilt angles in a randomized order. Between conditions, there was a 5-minute activity break. Differences in neck and shoulder posture, muscle activity, and discomfort between both tablet tilt angles and changes in the outcomes every 10 minutes over 40 minutes were investigated.

RESULTS

With the tilted tablet, there were lower neck flexion (Z = -4.637, P<0.001), lower shoulder extension (Z = -3.734, P<0.001), and lower neck Visual Analogue Scale (VAS) (left; Z = -4.699, P<0.001 and right; Z = -3.874, P<0.001) as compared to the no tilt condition. However, the right upper trapezius muscle activity was higher in the tilted condition as compared to the no tilt one. Over 40 minutes, the neck VAS (left; χ2(4) = 30.235, P<0.001 and right; χ2(4) = 32.560, P<0.001) and heart rate variability (χ2(4) = 12.906, P = 0.012) showed notable increases after 20 minutes compared to baseline.

CONCLUSION

In conclusion, adjusting the tablet tilt to 30° and limiting time spent to 20 minutes are recommended for young adults during the tablet writing to prevent neck problems.

Weaknesses of research methodologies on musculoskeletal disorders associated with mobile touch-screen devices

The objective of the currently study is to point out the weaknesses of some recent researches, which were done about the effects or symptoms of using Touch Screen Mobile Devices on the human musculoskeletal system. In this article, we reviewed the research processes performed in recent 26 randomly selected papers about musculoskeletal disorder to clarify the common weaknesses of these published articles. The electronic database search and reference search were conducted in four different databases: Medline, PubMed, Web of Science, and Scopus. We noticed that none of the reviewed papers had performed the experimental design phase of a scientific research. Additionally they had not validated the assumptions of the statistical methods used in their researches. Therefore, their findings are doubtful. In this article, we proposed practical outlines for a reliable experimental research.

Ergonomic arm support prototype device for smartphone users reduces neck and shoulder musculoskeletal loading and fatigue

Smartphone use is a risk factor for both neck and shoulder musculoskeletal disorders. The objective of this study was to evaluate an ergonomic arm support prototype device, which may help improve posture while using a smartphone, by determining its effect on muscle activity, muscle fatigue, and neck and shoulder discomfort. Twenty-four healthy young adult smartphone users performed 20 min of smartphone game playing under two different conditions, smartphone use with support prototype device (i.e. intervention condition) and without (i.e. control condition), while neck and shoulder posture were controlled at 0° neck flexion and 30° shoulder flexion. Activity and fatigue of four muscles were measured using surface electromyography (sEMG), these were: anterior deltoid (AD), cervical erector spinae (CES), upper trapezius (UT) and lower trapezius (LT). The intervention condition showed significantly decreased activity of all muscles. Fatigue of all muscles, except LT, significantly increased over time compared to the start point in the control condition. There was no significant difference in muscle fatigue between each time point in the intervention condition. In conclusion, the ergonomic arm support prototype device can be used as ergonomic intervention to reduce neck and shoulder muscle loading and fatigue.

Computer vision syndrome among Saudi population: An evaluation of prevalence and risk factors

Introduction

In the recent era of technological evolution, electronic devices have become an essential part of our lives, not merely in professional work settings, but also in daily leisure activities. Although these devices have simplified our lives, they are associated with a wide variety of health complaints. Thus, the so-called computer vision syndrome (CVS) has become a growing public health problem and has gained significant attention as it plays an important role in the quality of life of each individual, which in turn has put an increased burden on the health care system. Eye symptoms are among the most reported, yet extraocular symptoms were frequently described as adding an extra load.

Method

An electronic survey was distributed randomly through social media platforms among the general population in Saudi Arabia, between the period from July to December 2017, irrespective of their sociodemographic factors, aiming to determine the prevalence of CVS and to verify the most common associated risk factors.

Results

In total, 690 participants were involved in our study, with a mean age of 33.8 years. Of these, 77.6% suffer from CVS, with eye-burning being the most common ocular symptoms (71%), as well as itching (67.5%), blurred vision (65%), tearing (62.3%), and other eye symptoms being reported. Neck/shoulder pain was found to be the most prevalent extra ocular symptom (85.2%); also back pain and headache are frequently expressed (78% and 70% respectively). A significant positive correlation was observed between CVS symptoms and time spent using the devices (P-value: 0.002).

Conclusion

As technology advances, electronic devices have become a common tool that is used for different purposes on daily basis. We found in our study that the so-called computer vision syndrome is a growing public health problem. Thus, community education about the impact of such a lifestyle for proper handling of electronic devices must be addressed to avoid such health complaints.

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.

Influence of virtual keyboard design and usage posture on typing performance and muscle activity during tablet interaction

This study aimed to determine the effects of virtual keyboard designs and postures on task performance and muscle activity during tablet use. Eighteen healthy adults were randomly assigned to one of three postures (DESK, LAP, BED) to complete six sessions of 60-minute typing on a tablet with three virtual keyboards (STD, WIDE, SPLIT) twice in an experimental laboratory. Keystroke dynamics and muscle activity of the forearm and neck-shoulder regions were measured by electromyography. The split virtual keyboard was found to be associated with faster typing speed (SPLIT vs STD, p = .015; SPLIT vs WIDE, p < .001) and decreased muscle activity of extensor digitorum communis (SPLIT vs STD, p = .021). Lap posture was associated with faster typing speed (p = .018) and higher forearm muscle activity (p < .05). Typing performance decreased (p < .001) with elevated neck extensor muscle activity (p = .042) when the task duration prolonged. The split virtual keyboard showed potential to improve tablet ergonomics under various postures. Practitioner Summary: Tablets have become widely used for a variety of tasks and have gradually expanded into the realm of mobile productivity and education. Adequate designs of virtual keyboards for tablets show the potential for increased task performance and decreased muscle activity pertinent to typing activity and posture constraints imposed by non-traditional work positions. Abbreviations: WPM: words per minute; IKI: inter-key press interval; EMG: electromyography; EDC: extensor digitorum communis; FDS: flexor digitorum superficialis; CES: cervical erector spinae; UT: upper trapezius; EA: electrical activity; MVC: maximum voluntary contraction; APDF: amplitude probability distribution function.

A novel approach to bi-objective optimization of touch-screen installation position for minimizing physical workload and increasing screen visibility

The aim of this study was to propose a new method for optimizing the touch-screen installation position in order to minimize the physical workload and increase screen visibility. Ten students participated in this study. The participants utilized a touch screen at different installation heights (50, 65, and 80% of stature), tilt angles (0°, 45°, and 90° from the horizontal plane), and having different button sizes (a square with a side of 10, 20, and 30 mm). The joint angles, when using a touch screen, were measured to calculate the joint torque ratios (JTRs). Subjective screen visibility were also determined. The optimal installation position was determined by solving a bi-objective optimization problem consisting of two objective functions. The Pareto optimal solutions for the two objectives showed a range of 1124-1251 mm and 44.4-67.9°. The proposed method determined the optimal installation position of the touch screens.

Work-related risk factors for Carpal Tunnel Syndrome among Majmaah University female touchscreen users

Objectives:

This study aimed to explore the prevalence of carpal tunnel syndrome symptoms among female touchscreen users at Majmaah University, Saudi Arabia and to make a comparison for the wrist range of motion between probable CTS and non-CTS female touchscreen users.

Methods:

Two hundred and twenty-two female touchscreen users were enrolled in the present study. Among this cohort, fifty-two were academic members, 40 were employees and 130 were undergraduates. A Digital Inclinometer device was used to assess ROM of the wrist movements. A computer-based questionnaire, Phalen’s test, and Tinel’s sign were used to investigate the presence of CTS symptoms. The study was conducted between November 2018 and February 2019 at Majmaah University.

Results:

The prevalence of probable CTS was 34.2% among touchscreen users; the percent of probable CTS was significantly higher in undergraduates compared to other touchscreen users. There was a significant reduction in wrist flexion between the tested groups.

Conclusion:

Female touchscreen users at Majmaah University tended to have a high-risk for CTS. Wrist ROM measurements, particularly wrist flexion, could be a beneficial indicator for anticipating deviations in wrist posture after long-term touchscreen use. It is necessary to consider the job nature, age, BMI, and duration of using touchscreen as risk factors for CTS symptoms.

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.

Differences in posture kinematics between using a tablet, a laptop, and a desktop computer in sitting and in standing

BACKGROUND

Alternative methods of accessing the internet and performing computing-related work tasks are becoming common, e.g., using tablets or standing workstations. Few studies examine postural differences while using these alternative methods.

OBJECTIVE

To assess neck and upper limb kinematics while using a tablet, laptop and desktop computer (sitting and standing).

METHODS

Differences in neck flexion/extension, lateral flexion, rotation; elbow flexion/extension; wrist flexion/extension, radial/ulnar deviation; and shoulder elevation in 30 participants were assessed in four conditions, three in sitting (tablet, laptop and desktop computer) and one in standing (desktop computer). Three-dimensional motion capture recorded posture variables during an editing task. Differences between variables were determined using one-way ANOVA with Bonferroni post-hoc tests.

RESULTS

Compared to the desktop (sitting), tablet and laptop use resulted in increased neck flexion (mean difference tablet 16.92°, 95% CI 12.79-21.04; laptop 10.92, 7.86-13.97, P < 0.001) and shoulder elevation (right; tablet 10.29, 5.27-15.11; laptop 7.36, 3.72-11.01, P < 0.001). There were no meaningful posture differences between the sitting and standing desktop.

CONCLUSIONS

These findings suggest that using a tablet or laptop may increase neck flexion, potentially increasing posture strain. Regular users of tablets/laptops should consider adjustments in their posture, however, further research is required to determine whether posture adjustments prevent or reduce musculoskeletal symptoms.

A comparison of upper body and limb postures across technology and handheld device use in college students

[Purpose] People using technology and handheld devices adopt postures of the upper limb and neck that could result in musculoskeletal pathology. Previous research has explored the postures assumed during isolated use of technology devices, such as a smartphone, however a comparison of posture assumed between multiple devices has not been completed. The purpose of this study was to compare the posture of the upper body and limb between handheld devices and technology. [Participants and Methods] Twenty one healthy college students completed this study. Pictures of participants were taken in a neutral posture and as they performed standard tasks with 3 devices (mobile phone, tablet, laptop). A mobile application calculated sagittal and coronal plane posture variables, which were compared between device conditions with an ANOVA and post-hoc tests. [Results] Head translation and angulation and shoulder angulation varied significantly between conditions in both planes. Shoulder translation varied significantly between conditions in the sagittal plane. Rib translation varied significantly between conditions in the coronal plane. Tablet use produced postures that were statistically different than the other devices. [Conclusion] Use of each device altered posture however, frequent, regular use of a tablet may produce greater deleterious effects than regular use of other handheld devices/technology.

Tablet form factors and swipe gesture designs affect thumb biomechanics and performance during two-handed use

Tablet computers' hardware and software designs may affect upper extremity muscle activity and postures. This study investigated the hypothesis that forearm muscle activity as well as wrist and thumb postures differ during simple gestures across different tablet form factors and touchscreen locations. Sixteen adult (8 female, 8 male) participants completed 320 tablet gestures across four swipe locations, with various tablet sizes (8″ and 10"), tablet orientations (portrait and landscape), swipe orientations (vertical and horizontal), and swipe directions (medial and radial). Three-dimensional motion analysis and surface electromyography measured wrist and thumb postures and forearm muscle activity, respectively. Postures and muscle activity varied significantly across the four swipe locations (p < .0001). Overall, swipe location closest to the palm allowed users to swipe with a more neutral thumb and wrist posture and required less forearm muscle activity. Greater thumb extension and abduction along with greater wrist extension and ulnar deviation was required to reach the target as the target moved farther from the palm. Extensor Carpi Radialis, Extensor Carpi Ulnaris, Flexor Carpi Ulnaris, Extensor Policis Brevis, and Abductor Pollicis Longus muscle activity also increased significantly with greater thumb reach (p < 001). Larger tablet size induced greater Extensor Carpi Radialis, Extensor Carpi Ulnaris, Flexor Carpi Ulnaris, Flexor Carpi Radialis, and Abductor Pollicis Longus muscle activity (p < .0001). The study results demonstrate the importance of swipe locations and suggest that the tablet interface design can be improved to induce more neutral thumb and wrist posture along with lower forearm muscle load.

Evaluating biomechanics of user-selected sitting and standing computer workstation

A standing computer workstation has now become a popular modern work place intervention to reduce sedentary behavior at work. However, user's interaction related to a standing computer workstation and its differences with a sitting workstation need to be understood to assist in developing recommendations for use and set up. The study compared the differences in upper extremity posture and muscle activity between user-selected sitting and standing workstation setups. Twenty participants (10 females, 10 males) volunteered for the study. 3-D posture, surface electromyography, and user-reported discomfort were measured while completing simulated tasks with each participant's self-selected workstation setups. Sitting computer workstation associated with more non-neutral shoulder postures and greater shoulder muscle activity, while standing computer workstation induced greater wrist adduction angle and greater extensor carpi radialis muscle activity. Sitting computer workstation also associated with greater shoulder abduction postural variation (90th-10th percentile) while standing computer workstation associated with greater variation for should rotation and wrist extension. Users reported similar overall discomfort levels within the first 10 min of work but had more than twice as much discomfort while standing than sitting after 45 min; with most discomfort reported in the low back for standing and shoulder for sitting. These different measures provide understanding in users' different interactions with sitting and standing and by alternating between the two configurations in short bouts may be a way of changing the loading pattern on the upper extremity.

Head, trunk and arm posture amplitude and variation, muscle activity, sedentariness and physical activity of 3 to 5 year-old children during tablet computer use compared to television watching and toy play

Young children (ages 3 to 5) are using mobile touchscreen technology, including tablet computers, yet little is known on the potential musculoskeletal and physical activity implications of its use. This within-subject laboratory study (n = 10) examined head, trunk and arm postures, upper trapezius muscle activity, and total body and upper limb physical activity during playing with tablets compared to during TV watching and playing with non-screen toys. Overall, this study found that during tablet play children had greater mean head, trunk and upper arm angles compared to both TV watching and toy play. Conversely, compared to toy play, children playing with tablets had lesser trunk, upper arm and elbow postural variation, lesser trapezius activity, more time sitting and lesser physical activity. Thus, to minimize potential musculoskeletal and sedentary risks, non-screen toy play should be encouraged and education and guidelines provided for parents and caretakers to support wise use of tablets.

The associations of mobile touch screen device use with musculoskeletal symptoms and exposures: A systematic review

BACKGROUND

The use of mobile touch screen devices (MTSDs) has increased rapidly over the last decade, and there are concerns that their use may have negative musculoskeletal consequences; yet evidence on the association of MTSD use with musculoskeletal symptoms and exposures is currently dispersed. The aim of this study was to systematically review available literature on musculoskeletal symptoms and exposures associated with MTSD use. The synthesised information may facilitate wise use of MTSDs and may identify areas in need of further research.

METHODS

EMBASE, Medline, Scopus, PsycINFO and Proquest electronic databases were searched for articles published up to June 2016, using keywords describing MTSD, musculoskeletal symptoms (e.g. pain, discomfort) and musculoskeletal exposures (e.g. posture, muscle activity). Two reviewers independently screened the articles, extracted relevant data and assessed methodological quality of included studies. Due to heterogeneity in the studies, a meta-analysis was not possible and a structured narrative synthesis of the findings was undertaken.

RESULTS

A total of 9,908 articles were screened for eligibility with 45 articles finally included for review. Included articles were of cross-sectional, case-control or experimental laboratory study designs. No longitudinal studies were identified. Findings were presented and discussed in terms of the amount, features, tasks and positions of MTSD use and its association with musculoskeletal symptoms and musculoskeletal exposures.

CONCLUSIONS

There is limited evidence that MTSD use, and various aspects of its use (i.e. amount of usage, features, tasks and positions) are associated with musculoskeletal symptoms and exposures. This is due to mainly low quality experimental and case-control laboratory studies, with few cross-sectional and no longitudinal studies. Further research is warranted in order to develop guidelines for wise use of MTSDs.

A biomechanical and physiological study of office seat and tablet device interaction

Twenty subjects performed typing tasks on a desktop computer and touch-screen tablet in two chairs for an hour each, and the effects of chair, device, and their interactions on each dependent measure were recorded. Biomechanical measures of muscle force, spinal load, and posture were examined, while discomfort was measured via heart rate variability (HRV) and subjective reports. HRV was sensitive enough to differentiate between chair and device interactions. Biomechanically, a lack of seat back mobility forced individuals to maintain an upright seating posture with increased extensor muscle forces and increased spinal compression. Effects were exacerbated by forward flexion upon interaction with a tablet device or by slouching. Office chairs should be designed with both the human and workplace task in mind and allow for reclined postures to off-load the spine. The degree of recline should be limited, however, to prevent decreased lumbar lordosis resulting from posterior hip rotation in highly reclined postures.

Effects of electronic device overuse by university students in relation to clinical status and anatomical variations of the median nerve and transverse carpal ligament

INTRODUCTION

This study investigates the results of a questionnaire, provocative tests, and ultrasonographic measurements of carpal tunnel morphological parameters in intensive and nonintensive electronic device users.

METHODS

Forty-eight university students (equal numbers of intensive and nonintensive users, ≥5 h/day and <5 h/day of electronic device usage, respectively) were randomly selected after questionnaire responses were received and evaluated clinically and by ultrasonography. All participants were right-handed.

RESULTS

Intensive users had significantly more positive results in Phalen's and Durkan's tests and reported more wrist/hand pain compared with nonintensive users (P < 0.05). Intensive users also had significantly larger median nerve cross-sectional areas, flattening ratios, and perimeters as well as greater bowing of the transverse carpal ligament compared with nonintensive users (P < 0.05).

DISCUSSION

Overuse of electronic devices may adversely affect the median nerve within the carpal tunnel and the transverse carpal ligament, resulting in numbness, tingling, and pain in the hand. Caution may be warranted when using handheld electronic devices. Muscle Nerve 56: 873-880, 2017.

Exploration of the associations of touch-screen tablet computer usage and musculoskeletal discomfort

BACKGROUND

Tablet users may be at high risk of developing physical discomfort because of their usage behaviors and tablet design.

OBJECTIVE

Investigate the usage of tablets, variations in head and neck posture associated with different tablet tilt angles, and the association of tablet use with users' musculoskeletal discomfort.

METHODS

A survey of users' subjective perceptions conducted by questionnaire and measurements of users' postures by a 3D Motion analysis system was used to explore the effects of tablet use.

RESULTS

The questionnaire results indicated that over half of the participants reported physical discomfort after using tablets, with the most prevalent discomfort in the neck and shoulders, and more intensity of discomfort for the back although only few participants experienced it. Chi-squared tests indicated that significantly more participants who tended to use tablet computers to play games reported having musculoskeletal discomfort after using a tablet. In addition, preferences for tablet tilt angles varied across tasks (reading and game playing). The results from the 3D motion analysis revealed that head and neck flexion angles were significantly reduced when the tablets were positioned at relatively steep tilt angles. Neck flexion angle was significantly higher in game playing.

CONCLUSIONS

These data add information regarding to the usage of tablet and its associations with physical discomfort (significantly more participants who tended to use tablet computers to play games reported having musculoskeletal discomfort after using a tablet). Steep tilt angles (such as 60°) may cause tablet users to decrease their head and neck flexion angles, which could lead to a more neutral, effortless, and ergonomically correct posture. Maintaining proper neck posture during active activities such as game playing is recommended to avoid neck discomfort.

The effects of forearm support and shoulder posture on upper trapezius and anterior deltoid activity

[Purpose] To assess the effects of forearm support and shoulder posture on upper trapezius and anterior deltoid activity. [Subjects and Methods] Twenty-three female university students were evaluated. Muscle activity was assessed by a portable surface electromyography (sEMG) system (Myomonitor IV, Delsys, USA). Upper trapezius and anterior deltoid activity were recorded in five shoulder flexion postures: 0°, 15°, 30°, 45° and 60° and in two conditions: with the forearm supported and unsupported. Descriptive data analysis was performed and statistical analysis was conducted by a multivariate analysis of variance with three repeated factors (posture, support and side). [Results] Three-way interactions were not significant. Two-way interaction was significant for support and posture for both muscles, indicating that the muscular activity depends on the forearm support and shoulder posture. The forearm support reduced upper trapezius and anterior deltoid activity for all shoulder flexion angles. The mean and standard deviation for this decrease was 7.8 (SD=4.6)% of the maximal voluntary contraction for anterior deltoid and 3.8 (SD=2.0)% of the maximal voluntary contraction for upper trapezius. In the unsupported condition, increasing the shoulder flexion angle caused an increase in the upper trapezius and anterior deltoid activation. [Conclusion] These results highlight the importance of using forearm support and to maintain neutral shoulder posture, when the upper arms are not supported, to reduce muscle activation. Thus, this study provides evidence about the effect of these recommendations to reduce muscular activity.

Index finger and thumb kinematics and performance measurements for common touchscreen gestures

This study aimed to quantify differences in 7 touchscreen gestures. Eighteen participants performed index finger tapping, sliding in 4 orthogonal directions, and index finger and thumb pinch and stretch gestures on a touchscreen tablet computer. We hypothesized that two finger gestures would require longer task completion time and greater finger joint excursions than sliding gestures using only the index finger. We measured task completion times and finger joint kinematics. Tapping showed the fastest average (±SD) task completion time, 567(190) ms, of all gestures (p < 0.001). Pinch had faster task completion time, 765(277) ms, than all single-finger sliding gestures (p < 0.001). Stretch was faster to complete at 843(317) ms (p < 0.001) than all sliding gestures except slide right. Stretch demonstrated greater mean index finger metacarpophalangeal flexion/extension joint excursions, 63(16)°, compared to sliding gestures, 34(10)°, and tapping, 27(13)° (p < 0.01). Overall, two-finger gestures were faster to complete and showed greater joint excursions than single-finger sliding gestures.

Exercise training and postural correction improve upper extremity symptoms among touchscreen smartphone users

BACKGROUND

Repetitive movements and poor posture are associated with over-use of smartphones when texting or playing games and significantly contribute to the symptoms of pain and discomfort in the upper extremities.

OBJECTIVE

This study investigated the effect of exercise training and postural correction on disabilities of the arm, shoulder, and hand (DASH), hand grip and key pinch strength among smartphone users.

METHODS

One hundred university students were randomly divided into two groups; the experimental group participated in a 12-week programme of exercise training and postural corrections. The control group were instructed to follow their usual routine for smartphone utilization. Measurements of DASH scores, hand grip strength, and key pinch grip strength were conducted before and after 12 weeks for both groups.

RESULTS

There were no significant differences between the start values of both groups for DASH scores, hand grip strength, and key pinch strength (p > 0.05). However, there was a significant improvement in all outcomes measured in the experimental group (p < 0.05), with significant changes in the outcomes of the control group.

CONCLUSION

Postural correction combined with a selected exercise training programme improved the hand grip, key pinch grip strength, and upper extremity disability and symptoms associated with smartphone use among university students.

Achieving occupational goals with the TAPit: A case study

Background/Aims:

The Touch Accessible Platform for Interactive Technology (TAPit) is an interactive learning station, with a large touch screen providing access to the Internet and other resources. The aim of this study was to investigate the physical, psychosocial and functional impact of the TAPit on an individual living with spinal cord injury.

Methods:

This study employed a mixed methods case study design. Quantitative data was analysed descriptively, and both quantitative and qualitative data was classified according to the dimensions.

Results:

The introduction of the TAPit to the participant addressed aspects of doing, being, becoming and belonging, and had an immediate and successful impact for her, as she achieved two long-held and meaningful goals during a short trial. Strengths and limitations for the TAPit were identified in regards to people with spinal cord injury, along with directions for future development.

Conclusions:

This case study provides the first evidence about the effectiveness of the TAPit as an item of assistive technology for people with spinal cord injury, including participant perspectives on its use. This study demonstrates its potential as a device to support people to be able to participate in meaningful activities and occupations and that the provision of suitable adaptations and apps are the key to its success.

Influence of Input Hardware and Work Surface Angle on Upper Limb Posture in a Hybrid Computer Workstation

OBJECTIVE

We evaluated the effect of work surface angle and input hardware on upper-limb posture when using a hybrid computer workstation.

BACKGROUND

Offices use sit-stand and/or tablet workstations to increase worker mobility. These workstations may have negative effects on upper-limb joints by increasing time spent in non-neutral postures, but a hybrid standing workstation may improve working postures.

METHOD

Fourteen participants completed office tasks in four workstation configurations: a horizontal or sloped 15° working surface with computer or tablet hardware. Three-dimensional right upper-limb postures were recorded during three tasks: reading, form filling, and writing e-mails. Amplitude probability distribution functions determined the median and range of upper-limb postures.

RESULTS

The sloped-surface tablet workstation decreased wrist ulnar deviation by 5° when compared to the horizontal-surface computer when reading. When using computer input devices (keyboard and mouse), the shoulder, elbow, and wrist were closest to neutral joint postures when working on a horizontal work surface. The elbow was 23° and 15° more extended, whereas the wrist was 6° less ulnar deviated, when reading compared to typing forms or e-mails.

CONCLUSION

We recommend that the horizontal-surface computer configuration be used for typing and the sloped-surface tablet configuration be used for intermittent reading tasks in this hybrid workstation.

APPLICATION

Offices with mobile employees could use this workstation for alternating their upper-extremity postures; however, other aspects of the device need further investigation.

Usage Position and Virtual Keyboard Design Affect Upper-Body Kinematics, Discomfort, and Usability during Prolonged Tablet Typing

Purpose

The increase in tablet usage allows people to perform computer work in non-traditional office environments. The aim of this study was to assess the effects of changes in tablet keyboard design on postures of the upper extremities and neck, discomfort, and usability under different usage positions during prolonged touch-typing.

Methods

Eighteen healthy participants familiar with touch-screen devices were randomized into three usage positions (desk, lap, and bed) and completed six, 60-minute typing sessions using three virtual keyboard designs (standard, wide, split). Electrogoniometers continuously measured the postures of the wrists, elbow, and neck. Body discomfort and system usability were evaluated by questionnaires before and immediately after each typing session.

Results

Separate linear mixed effects models on various postural measures and subjective ratings are conducted with usage position as the between-subject factors, keyboard design and typing duration as the with-in subject factors were conducted. Using the tablet in bed led to more extended wrists but a more natural elbow flexion than the desk position. The angled split virtual keyboard significantly reduced the extent of wrist ulnar deviation than the keyboard with either standard or wide design. However, little difference was observed across the usage position and keyboard design. When the postural data were compared between the middle and end of typing sessions, the wrists, elbow, and neck all exhibited a substantially increased range of joint movements (13% to 38%). The discomfort rating also increased significantly over time in every upper body region investigated. Additionally, the split keyboard design received a higher usability rating in the bed position, whereas participants had more satisfactory experience while using the wide keyboard in the traditional desk setting.

Conclusions

Prolonged use of tablets in non-traditional office environments may result in awkward postures in the upper body that may expose users to greater risks of developing musculoskeletal symptoms. Adequate virtual keyboard designs show the potential to alleviate some postural effects and improve the user experience without changing the tablet form factors.

Mobile input device type, texting style and screen size influence upper extremity and trapezius muscle activity, and cervical posture while texting

This study aimed to determine the effects of input device type, texting style, and screen size on upper extremity and trapezius muscle activity and cervical posture during a short texting task in college students. Users of a physical keypad produced greater thumb, finger flexor, and wrist extensor muscle activity than when texting with a touch screen device of similar dimensions. Texting on either device produced greater wrist extensor muscle activity when texting with 1 hand/thumb compared with both hands/thumbs. As touch screen size increased, more participants held the device on their lap, and chose to use both thumbs less. There was also a trend for greater finger flexor, wrist extensor, and trapezius muscle activity as touch screen size increased, and for greater cervical flexion, although mean differences for cervical flexion were small. Future research can help inform whether the ergonomic stressors observed during texting are associated with musculoskeletal disorder risk.

Gravitational demand on the neck musculature during tablet computer use

Tablet computer use requires substantial head and neck flexion, which is a risk factor for neck pain. The goal of this study was to evaluate the biomechanics of the head-neck system during seated tablet computer use under a variety of conditions. A physiologically relevant variable, gravitational demand (the ratio of gravitational moment due to the weight of the head to maximal muscle moment capacity), was estimated using a musculoskeletal model incorporating subject-specific size and intervertebral postures from radiographs. Gravitational demand in postures adopted during tablet computer use was 3-5 times that of the neutral posture, with the lowest demand when the tablet was in a high propped position. Moreover, the estimated gravitational demand could be correlated to head and neck postural measures (0.48 < R(2) < 0.64, p < 0.001). These findings provide quantitative data about mechanical requirements on the neck musculature during tablet computer use and are important for developing ergonomics guidelines. Practitioner Summary: Flexed head and neck postures occur during tablet computer use and are implicated in neck pain. The mechanical demand on the neck muscles was estimated to increase 3-5 times during seated tablet computer use versus seated neutral posture, with the lowest demand in a high propped tablet position but few differences in other conditions.

Holding a tablet computer with one hand: effect of tablet design features on biomechanics and subjective usability among users with small hands

The purpose of this study was to evaluate tablet size (weight), orientation, grip shape, texture and stylus shape on productivity, biomechanics and subjective usability and fatigue when the tablet was held with just the left hand. A total of 15 male and 15 female subjects, ages 16-64 years, tested eight tablets and three styluses. Overall, the usability, fatigue and biomechanical evaluation of tablet design features supported the use of smaller to medium-sized tablets, with a ledge or handle shape on the back and surfaced with a rubberised texture. Larger, heavier tablets had significantly worse usability and biomechanics and their use with one hand should be limited. The stylus with a tapered grip (7.5-9.5 mm) or larger grip (7.6 mm) had better usability and biomechanics than one with a smaller grip (5 mm). There were no significant differences in productivity between design features. These design parameters may be important when designing tablets.

PRACTITIONER SUMMARY

Different tablet and stylus design features were evaluated for usability and biomechanical properties. On the basis of short-term tasks, emulating functional tablets, usability was improved with the smaller and medium-sized tablets, portrait (vs. landscape) orientation, a back ledge grip and rubberised texture. There were no differences in productivity between design features.