User discomfort, work posture and muscle activity while using a touchscreen in a desktop PC setting

The impact of remote work using mobile information and communication technologies on physical health: a systematic review

Remote e-working with information and communication technology (ICT) has long been on the rise, with its implementation accelerated by mandatory working from home regulations during the COVID-19 pandemic. This systematic literature review summarises the influencing factors of ICT-based remote e-working (device types, duration of use, user interfaces, etc.) on the physical health (musculoskeletal system and eyes) of knowledge workers. A search in four electronic databases and a manual search in four German journals resulted in 21 articles being included in this review. A bias analysis was conducted for all articles. Unfavourable postures, inappropriate working devices and certain environmental factors may cause a range of physical complaints, even after comparably short periods of time. Mostly, these complaints are greater compared to those experienced when working on a fully equipped stationary computer. Therefore, remote e-working requires careful planning, awareness, and the willingness to embrace working situations that counteract these problems.

Perceived Discomfort, Neck Kinematics, and Muscular Activity During Smartphone Usage: A Comparative Study

OBJECTIVE

The present study aims to evaluate the effects of posture, task, and handgrip style on discomfort, neck kinematics, and concomitant muscular activity when using a smartphone (SP).

BACKGROUND

Along with the popularity of smartphones, musculoskeletal disorders have become prevalent among smartphone users. However, comprehensive aspects of discomfort, kinematics, and electromyographic responses across various conditions remain to be investigated.

METHOD

Twenty-four young smartphone users performed typing, video watching, and reading tasks while holding the smartphone both with one hand and with two hands while either sitting or standing. Neck kinematics and muscular activities were simultaneously recorded.

RESULTS

Working with SPs led to higher discomfort in the neck (p = 0.01), lower back (p = 0.01), and shoulder (p = 0.04) while sitting as compared to standing. Sitting was associated with greater neck flexion and more minor lateral bending for all tasks and grip styles (p < 0.05). Electromyographic analysis indicated significant differences between sitting and standing, with alterations being dependent on the test condition. Moreover, neck kinematics and muscular activities significantly differed based on the task nature, handgrip, and interactions.

CONCLUSION

This study highlights the risk of using smartphones in increased neck angle flexion and muscular activities fatigue. Thus, posture and handgrip should be considered while using SPs. As each test condition affects a specific dependent variable, a holistic approach is required to evaluate the responses of SP users' musculoskeletal systems.

APPLICATION

Results can be applied to develop guidelines for musculoskeletal disorders/discomfort prevention among SP users, especially with the rise of smartphone use during the COVID-19 pandemic.

Excessive use of electronic devices among children and adolescents is associated with musculoskeletal symptoms, visual symptoms, psychosocial health, and quality of life: a cross-sectional study

Objective

Electronic devices have become an indispensable part of our daily lives. The frequency and duration of device use in children and adolescents have increased drastically over the years and the study of its negative musculoskeletal, visual and psychosocial health impacts is necessary.

Materials and methods

This cross-sectional study aimed to evaluate the associations between electronic device use and the prevalence and severity of musculoskeletal symptoms, visual symptoms, psychosocial health, and quality of life in children and adolescents studying at primary and secondary schools. Data were collected through confidential online and paper-and-pencil questionnaires. Primary 4-5 and Secondary 1-4 students were recruited from 3 schools in Hong Kong. Demographics, frequency and duration of electronic device use, frequencies of musculoskeletal symptoms, visual symptoms, psychosocial health, and quality of life outcomes were measured.

Results

1,058 children and adolescents aged 9-17  years participated. Sixty-one percent and 78% of all students spent more than 2  h per day using electronic devices during school days and weekend/holidays, respectively. Extended electronic device use was associated with increased prevalence and severity of musculoskeletal symptoms (ρ's = 0.28-0.33, P's < 0.001), visual symptoms (ρ's = 0.33-0.35, P's < 0.001), and poorer device use-related psychosocial health (ρ's = 0.38-0.47, P's < 0.001). Secondary school students reported greater device use and severity of symptoms than primary school students.

Conclusion

Excessive electronic device use was associated with increased prevalence and severity of physical and psychosocial symptoms, and such use is more prevalent in adolescents when compared to the children. The findings have important health implications for children and adolescents, suggesting that early intervention is needed to reduce the risk of developing device use-related disorders.

A passive upper-limb exoskeleton reduced muscular loading during augmented reality interactions

The aim of this study was to evaluate a passive upper-limb exoskeleton as an ergonomic control to reduce the musculoskeletal load in the shoulders associated with augmented reality (AR) interactions. In a repeated-measures laboratory study, each of the 20 participants performed a series of AR tasks with and without a commercially-available upper-limb exoskeleton. During the AR tasks, muscle activity (anterior, middle, posterior deltoid, and upper trapezius), shoulder joint postures/moment, and self-reported discomfort were collected. The results showed that the exoskeleton significantly reduced muscle activity in the upper trapezius and deltoid muscle groups and self-reported discomfort. However, the shoulder postures and task performance measures were not affected by the exoskeleton during the AR interactions. Given the significant decrease in muscle activity and discomfort without compromising task performance, a passive exoskeleton can be an effective ergonomic control measure to reduce the risks of developing musculoskeletal discomfort or injuries in the shoulder regions.

Suboccipital Muscles, Forward Head Posture, and Cervicogenic Dizziness

Dizziness or vertigo can be caused by dysfunction of the vestibular or non-vestibular systems. The diagnosis, treatment, and mechanism of dizziness or vertigo caused by vestibular dysfunction have been described in detail. However, dizziness by the non-vestibular system, especially cervicogenic dizziness, is not well known. This paper explained the cervicogenic dizziness caused by abnormal sensory input with references to several studies. Among head and neck muscles, suboccipital muscles act as stabilizers and controllers of the head. Structural and functional changes of the suboccipital muscles can induce dizziness. Especially, myodural bridges and activation of trigger point stimulated by abnormal head posture may be associated with cervicogenic dizziness.

Impact of Digital Device Use on Neck and Low Back Pain Intensity among Nursing Students at a Saudi Government University: A Cross-Sectional Study

As digital technology and online activities have become more widely accessible over the past few years, information and communication technology have grown in importance in all students' lives. Most of them routinely use digital devices for a range of activities, primarily for online learning, activities, assignments, conversing, and Internet browsing. This study elucidated the relationship between neck and low back pain intensity and the use of digital devices among Saudi nursing students. A cross-sectional descriptive exploratory research design was applied using a convenience sample of 120 nursing students enrolled in an undergraduate nursing program at a Saudi government university located in Riyadh, the capital city of Saudi Arabia. A valid and reliable self-administered survey was employed. Data about sociodemographic characteristics, the Neck Disability Index and the Roland-Morris Disability Questionnaire were collected. The participants reported 9.1 ± 4.6 study hours on average per week. A total of 82.5% of them do not receive enough exercise, and 87.5% indicated daily use of digital devices. Around half (54.2%) of participants reported having neck pain of a mild intensity. About 60% of the participants regularly shift positions to rest their backs, 39.2% are only able to stand for limited periods due to back issues, and 39.2% expressed concern for others about what might happen to their health. Although there was an association between neck pain intensity and the age or gender of all research participants, there was a significant association between neck pain severity and marital status (χ² = 15.226, p = 0.019). Our findings suggest that nursing students should maintain neutral neck and back postures on a regular basis to reduce pain, which could be attributed to extensive reading on digital devices.

Automated Detection of Improper Sitting Postures in Computer Users Based on Motion Capture Sensors

Prolonged computer-related work can be linked to musculoskeletal disorders (MSD) in the upper limbs and improper posture. In this regard, we report on developing resources supporting improper posture studies based on motion capture sensors. These resources were used to create a baseline detector for the automated detection of improper sitting postures, which was next used to evaluate the applicability of Hjorth’s parameters—Activity, Mobility and Complexity—on the specific classification task. Specifically, based on accelerometer data, we computed Hjorth’s time-domain parameters, which we stacked as feature vectors and fed to a binary classifier (kNN, decision tree, linear SVM and Gaussian SVM). The experimental evaluation in a setup involving two different keyboard types (standard and ergonomic) validated the practical worth of the proposed sitting posture detection method, and we reported an average classification accuracy of up to 98.4%. We deem that this research contributes toward creating an automated system for improper posture monitoring for people working on a computer for prolonged periods.

Mobile phone usage among Nigerians: Risk factors for musculoskeletal injuries and preventive strategies

AIMS

The increase in the usage of hand-held devices (HHDs) and smartphones (SPs), especially in Nigeria has resulted in an upsurge of musculoskeletal complaints. The aim of this study was to determine the incidence and risk factors for musculoskeletal injuries due to mobile phone usage among Nigerians and the preventive strategies.

MATERIALS AND METHODS

This study involved 630 male and female participants above 18 years old who were purposively recruited across designated study centres in public places. The instrument used was a questionnaire specifically designed to suit the Nigerian culture and environment and developed from previously validated questionnaires. Data were exported to Statistical Computing Programming R version 4.0.5 for analysis and Chi-square was used to compare the characteristics of those who experienced injury using SPs/HHDS and those who did not. Independent variables with a 95% confidence level and P < 0.05 in the multivariate model were considered statistically significant.

RESULTS

The most common daily use of SPs/HHDS by the participants was phone calls (98.4%) followed closely by social networking (96.0%) while the occupation and educational level of the participants had statistically significant (P < 0.05) impact on musculoskeletal injuries. The type of mobile device and the time spent using these devices were also significant (P < 0.05) risk factors for injuries. Some self-treatment strategies adopted by the participants were all significantly (P < 0.05) associated with reduction of musculoskeletal discomfort.

CONCLUSION

The occupation, educational level, the types of mobile devices and time spent using the devices were risk factors for musculoskeletal injuries.

Effects of smartphone screen viewing duration and body position on head and neck posture in elementary school children

BACKGROUND

Electronic media have become integral parts of modern life, in which prolonged screen viewing time (SVT) by children is nearly unavoidable. Prolonged use of smartphones could lead to musculoskeletal problems.

OBJECTIVES

To investigate the effect of SVT on head and neck posture during and after using smartphones for various periods of time in either standing or sitting postures.

METHODS

This observational study included 34 male children aged 5-12 years who were assigned to one of two groups based on average smartphone use duration per day: group A comprised 18 children averaging > 4 hours per day (h/day) of smartphone use, and group B comprised 16 children with < 4 h/day of smartphone use. The children's postures were photographed in standing and sitting positions while using a smartphone and 30 min after ceasing smartphone use. The head flexion, neck flexion, gaze, and craniocervical angles were measured using the software program Kinovea.

RESULTS

Significant increases were found in head flexion, neck flexion, and gaze angles. Furthermore, both groups saw a significant decrease in craniocervical angle when sitting compared to when standing, both during and 30 min after smartphone use. The head flexion, neck flexion, and gaze angles of group A were significantly higher than those of group B, and the craniocervical angle of group A was significantly lower than that of group B in both postures (p< 0.05).

CONCLUSION

SVT is associated with increased neck and head flexion posture in children, especially in a sitting position.

The Association of Smartphone Usage Duration with Physical Fitness among Chinese University Students

BACKGROUND

The use of smartphones has become increasingly prevalent in recent years, especially among the youth. However, smartphone overuse has been reported to be related to several negative mental and physical health outcomes. Although the association between smartphone use and physical fitness has been investigated in several studies, these studies only focused on specific elements of physical fitness, such as grip strength. In addition, evidence on young adults is limited. Thus, this study aimed to examine the association between the duration of smartphone use and physical fitness among Chinese university students.

METHODS

A total of 11,242 university students volunteered to participate in the study. The duration of smartphone use was assessed using a self-reported questionnaire. Physical fitness tests consisted of a 50-m sprint and vital capacity tests for both sexes, a 1000-m run and pull-up test for male students, and an 800-m run and sit-up test for female students.

RESULTS

The duration of smartphone use among the participants was 5.4 h/day for male students and 6.1 h/day for female students on average. After adjusting for confounding factors, in male students, a long duration of smartphone use was significantly associated with a slow 50 m sprint and 1000 m run time, lower pull-up times, and poor vital capacity (p = 0.004, 0.002, 0.002 and 0.040, respectively). In female students, a long duration of smartphone use was associated with a slow 800 m run time (p < 0.001).

CONCLUSION

This study found that longer duration of smartphone use was associated with lower physical fitness among Chinese university students. The duration of smartphone use may be an influencing factor for physical fitness.

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.

Evaluation of the biomechanical stress in the neck and shoulders during augmented reality interactions

This study aimed to characterize the biomechanical stresses in the neck and shoulder, self-reported discomfort, and usability by different target distance or size during augmented reality (AR) interactions. In a repeated-measures laboratory-based study, 20 participants (10 males) performed three standardized AR tasks (3-dimensional (3-D) cube, omni-directional pointing, and web-browsing tasks) with three target distances (0.3, 0.6, and 0.9 m from each participant denoted by near, middle, far targets) for the 3-D cube and omni-directional pointing tasks or three target sizes: small (30% smaller than default), medium (default: 1.0 × 1.1 m), and large (30% larger than default) for the web-browsing task. Joint angle, joint moment, muscle activity, self-reported discomfort and comfort in the neck and shoulders; and subjective usability ratings were measured. The results showed that shoulder angle (flexion and abduction), shoulder moment (flexion), middle deltoid muscle activity significantly increased as the target distance increased during the 3-D cube task (p's < 0.001). Self-reported neck and shoulder discomfort significantly increased after completing each task (p's < 0.001). The participants preferred the near to middle distance (0.3-0.6 m) or the medium to large window size due to task easiness (p's < 0.005). The highest task performance (speed) was occurred at the near distance or the large window size during the 3-D cube and web-browsing tasks (p's < 0.001). The results indicate that AR interactions with the far target distance (close to maximum reach envelop) may increase the risk for musculoskeletal discomfort in the shoulder regions. Given the increased usability and task performance, the near to middle distance (less than 0.6 m) or the medium to large window size (greater than 1.0 × 1.1 m) would be recommended for AR interactions.

Design and evaluation of an ergonomic chair for near-ground welding based on muscle activity and usability

BACKGROUND

Work-related musculoskeletal disorders (WMSDs) are one of the major problems in industrial societies. Awkward postures in theworkplace are considered as a main reasons for these disorders. Therefore, the study and investigation of postures to improve them (in the workplace) have a significant role in appropriate intervention.

OBJECTIVE

This study aimed to design an ergonomic chair for near-ground welding operations and evaluate its impact on the electromyography (EMG) activity of a select group of lower limb muscles.

METHODS

The EMG activity of lower limb muscles was measured in eight postures consisting of three postures identified via observing welders at work, and five on-chair postures suggested for chair use during welding. The usability of the designed chair was evaluated through the use of the System Usability Scale (SUS).

RESULTS

The results showed that the suggested on-chair postures had significantly lower mean muscle activity compared with the identified postures (p < 0.001). Among the identified postures, kneeling posture had the lowest mean muscle activity (p < 0.01), still significantly higher than the mean activity of the on-chair postures (p < 0.001). Applying a 15° slope to the seat pad led to a decrease in muscle activity and an increase in usability score. The usability score of the chair was acceptable in all postures except KCC-90 posture.

CONCLUSIONS

Using a suitable chair or support for different work postures can prevent detrimental muscle activities during work and the development of musculoskeletal disorders caused by intense muscle activity due to awkward postures.

Future technology on the flight deck: assessing the use of touchscreens in vibration environments

Use of touchscreens in the flight deck has been steadily increasing, however, their usability may be severely impacted when turbulent conditions arise. Most previous research focusses on using touchscreens in static conditions; therefore, this study assessed touchscreen use whilst undergoing turbulent representative motion, generated using a 6-axis motion simulator. Touchscreens were tested in centre, side and overhead positions, to investigate how turbulence affected: (1) error rate, movement times and accuracy, (2) arm fatigue and discomfort. Two touchscreen technologies were compared: a 15" infra-red and a 17.3" projected capacitive touchscreen with force sensing capability. The potential of the force sensing capability to minimise unintentional interactions was also investigated. Twenty-six participants undertook multi-direction tapping (ISO 9241; ISO 2010 ) and gesture tasks, under four vibration conditions (control, light chop, light turbulence and moderate turbulence). Error rate, movement time and workload increased and usability decreased significantly, with screen position and increasing turbulence level. Practitioner Summary: This study evaluated the use of infra-red and projected capacitive touchscreen technologies using multi-directional tapping and gesture tasks, whilst being subjected to different levels of turbulence representative motion. Performance degraded significantly with increasing turbulence level and touchscreen location. This has implications for future flight deck design.

The Healthy e-Elderly People Assessment (HEPA) application

Purpose

The purpose of this paper is to evaluate health effects and determine the factors associated with health effects from smartphone and tablet use among the elderly in Thailand.

Design/methodology/approach

This study was a cross-sectional descriptive study. The participants comprised 490 elderly people. A self-administered questionnaire was used for data collection via the Healthy e-Elderly People Assessment mobile application in the Android operating system by Google which consists of five parts of a questionnaire. The variables were analyzed using SPSS such as frequency, percentage, mean and binary logistic regression.

Findings

Altogether, the participants were 223 males and 267 females; mean age=64.9±5.4. The average time spent using a mobile device was 2.8±1.9 h/day. Participants recorded that after use of either device, 59.0 percent experienced eye pain, 52.7 percent experienced dim eyes, 30.2 percent experienced tiredness, and 28.0 percent experienced moodiness. Socially, 26.8 percent recorded changes in social interaction. Periods of time using devices, time consumed in device usage (hours/day), the type of application, and the difference in times of use, place of usage and time spent in rest breaks from smartphone or tablet usage were significantly associated with health effects (p<0.05).

Originality/value

The elderly users may be at risk of several health effects from smartphone and tablet use. The potential gap in knowledge conceals some of the risk factors for the current health effects. Practical intervention to reduce health effects from the use of smartphones and tablets should be considered.

Armrests and back support reduced biomechanical loading in the neck and upper extremities during mobile phone use

Mobile phone use is known to be associated with musculoskeletal pain in the neck and upper extremities because of related physical risk factors, including awkward postures. A chair that provides adequate support (armrests and back support) may reduce biomechanical loading in the neck and shoulder regions. Therefore, we conducted a repeated-measures laboratory study with 20 participants (23 ± 1.9 years; 10 males) to determine whether armrests and back support during mobile phone use reduced head/neck flexion, gravitational moment, and muscle activity in the neck and shoulder regions. The results showed that the chair support (armrests and back support) reduced head/neck flexion (p < 0.001), gravitational moment (p < 0.001), and muscle activity (p < 0.01) in the neck and shoulder regions significantly compared to no chair support. These results indicate that a chair with adequate support can be an effective intervention to reduce the biomechanical exposures and associated muscular pain in the neck and shoulders during mobile phone use.

Posture and discomfort assessment in computer users while using touch screen device as compared with mouse-keyboard and touch pad-keyboard

BACKGROUND

Touch screen computers require significant arm and hand movements. This can result to body discomfort and biomechanical load in users.

OBJECTIVES

This study was carried out to examine posture and users' discomfort while using touch screen device as compared with mouse-keyboard and touch pad-keyboard.

METHODS

Twenty three (23) students participated in this experimental study. The subjects completed pre-defined tasks in three 15 min trials by means of touch screen, touch pad-keyboard and mouse-keyboard as input devices. Postural angles were measured by Qualisys motion capture system. Body discomfort was assessed by a 10-cm visual analog scale. Rating scale was employed to assess the perception of subjects on the posture of body parts while utilizing the three devices.

RESULTS

There was no significant difference in head inclination when using the three types of devices. Nevertheless, the mean of neck (p = 0.005) and trunk (p < 0.0001) inclinations as well as arm angle (p < 0.0001) while using touch screen, differed significantly from the two other devices and were more deviated from neutral posture. The type of input device was found to have significant effect on the right shoulder (p = 0.017), right elbow (p = 0.031), right wrist/hand (p = 0.004) and whole body discomfort (p = 0.026). Touch screen caused more discomfort in the mentioned regions when compared to the other two devices. Friedman test showed that differences of mean ratings for perceived shoulder and elbow postures in the 3 trials were significant (p = 0.005 and p = 0.011, respectively). Touch screen was the most unfavorable input device based on the subjects' judgment.

CONCLUSION

Touch screen caused more deviated postural angles, increased body discomfort and unfavorable postures.

Upper thoracic spine mobilization and mobility exercise versus upper cervical spine mobilization and stabilization exercise in individuals with forward head posture: a randomized clinical trial

Background

Although upper cervical and upper thoracic spine mobilization plus therapeutic exercises are common interventions for the management of forward head posture (FHP), no study has directly compared the effectiveness of cervical spine mobilization and stabilization exercise with that of thoracic spine mobilization and mobility exercise in individuals with FHP.

Methods

Thirty-two participants with FHP were randomized into the cervical group or the thoracic group. The treatment period was 4 weeks, with follow-up assessment at 4 and 6 weeks after the initial examination. Outcome measures including the craniovertebral angle (CVA), cervical range of motion, numeric pain rating scale (NPRS), pressure pain threshold, neck disability index (NDI), and global rating of change (GRC) were collected. Data were examined with a two-way repeated-measures analysis of variance (group × time).

Results

Participants in the thoracic group demonstrated significant improvements (p < .05) in CVA, cervical extension, NPRS, and NDI at the 6-week follow-up compared with those in the cervical group. In addition, 11 of 15 (68.8%) participants in the thoracic group compared with 8 of 16 participants (50%) in the cervical group showed a GRC score of +4 or higher at the 4-week follow-up.

Conclusions

The combination of upper thoracic spine mobilization and mobility exercise demonstrated better overall short-term outcomes in CVA (standing position), cervical extension, NPRS, NDI, and GRC compared with upper cervical spine mobilization and stabilization exercise in individuals with FHP.

Trial registration

KCT0002307, April 11, 2017 (retrospectively registered).

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.

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.

Effects of touch target location on performance and physical demands of computer touchscreen use

Touchscreen interfaces for computers are known to cause greater physical stress compared to traditional computer interfaces. The objective of this study was to evaluate how physical demands and task performance of a tap gesture on a computer touchscreen vary between target locations and display positions. Twenty-three healthy participants conducted reach-tap-return trials with touch targets at fifteen locations in three display positions. Mean completion time, touch accuracy and electromyography of the shoulder and neck extensor muscles were compared between the target locations and display positions. The results demonstrated that participants completed the trial 12%-27% faster with 13%-39% less muscle activity when interacting with targets in the lower area of the display compared to when tapping upper targets (p < 0.05). The findings suggest that proper target placement and display positioning can improve task performance and lessen physical demands of computer touchscreen interface use.

Touchscreen interfaces in context: A systematic review of research into touchscreens across settings, populations, and implementations

Although many studies have been conducted on the human factors and ergonomics (HFE) of touchscreens, no comprehensive review has summarized the findings of these studies. Based on a schema (three dimensions of understanding critical for successful display selection) presented by Wickens et al. (2004), we identified three dimensions of analysis for touchscreen implementations: touchscreen technology, setting and environment of implementation, and user population. We conducted a systematic review based on the PRISMA protocol (Moher et al., 2009), searching five article databases for relevant quantitative literature on touchscreens. We found that all three dimensions of analysis have a significant effect on the HFE of touchscreens, and that a selection for or against touchscreens must take into consideration the specific context of system interaction in order to maximize safety, performance, and user satisfaction. Our report concludes with a set of specific recommendations for systems designers considering touchscreens as input/output devices, and suggestions for future study into the HFE of touchscreens.

Assessing ergonomic risks of software: Development of the SEAT

Software utilizing interaction designs that require extensive dragging or clicking of icons may increase users' risks for upper extremity cumulative trauma disorders. The purpose of this research is to develop a Self-report Ergonomic Assessment Tool (SEAT) for assessing the risks of software interaction designs and facilitate mitigation of those risks. A 28-item self-report measure was developed by combining and modifying items from existing industrial ergonomic tools. Data were collected from 166 participants after they completed four different tasks that varied by method of input (touch or keyboard and mouse) and type of task (selecting or typing). Principal component analysis found distinct factors associated with stress (i.e., demands) and strain (i.e., response). Repeated measures analyses of variance showed that participants could discriminate the different strain induced by the input methods and tasks. However, participants' ability to discriminate between the stressors associated with that strain was mixed. Further validation of the SEAT is necessary but these results indicate that the SEAT may be a viable method of assessing ergonomics risks presented by software design.

A literature review of the effects of computer input device design on biomechanical loading and musculoskeletal outcomes during computer work

BACKGROUND

Extended use of conventional computer input devices is associated with negative musculoskeletal outcomes. While many alternative designs have been proposed, it is unclear whether these devices reduce biomechanical loading and musculoskeletal outcomes.

OBJECTIVE

To review studies describing and evaluating the biomechanical loading and musculoskeletal outcomes associated with conventional and alternative input devices.

METHODS

Included studies evaluated biomechanical loading and/or musculoskeletal outcomes of users' distal or proximal upper extremity regions associated with the operation of alternative input devices (pointing devices, mice, other devices) that could be used in a desktop personal computing environment during typical office work.

RESULTS

Some alternative pointing device designs (e.g. rollerbar) were consistently associated with decreased biomechanical loading while other designs had inconsistent results across studies. Most alternative keyboards evaluated in the literature reduce biomechanical loading and musculoskeletal outcomes. Studies of other input devices (e.g. touchscreen and gestural controls) were rare, however, those reported to date indicate that these devices are currently unsuitable as replacements for traditional devices.

CONCLUSIONS

Alternative input devices that reduce biomechanical loading may make better choices for preventing or alleviating musculoskeletal outcomes during computer use, however, it is unclear whether many existing designs are effective.

Effect of duration of smartphone use on muscle fatigue and pain caused by forward head posture in adults

[Purpose] The effect of duration of smartphone use on neck and shoulder muscle fatigue and pain was investigated in adults with forward head posture. [Subjects and Methods] Thirty-four adults with forward head posture were classified into groups by duration of smartphone use: 11 used a smartphone for 10 minutes each (group 1), 12 for 20 minutes each (group 2), and 11 for 30 minutes each (group 3). Fatigue cervical erector spinae and upper trapezius muscles was measured by electromyography, and pain before and after the experiment was evaluated using Visual Analog Scale (VAS) scores. [Results] There was a significant difference in the degree of fatigue in the left upper trapezius muscles in group 2 and left cervical erector spinae and bilateral upper trapeziuses group 3. There was a significant difference in fatigue in the left upper trapezius in groups 1 and 3. The VAS showed significant differences in all groups before and after the experiment and between groups 1 and 3. [Conclusion] Pain and fatigue worsened with longer smartphone use. This study provided data on the proper duration of smartphone use. Correct posture and breaks of at least 20 minutes are recommend when using smartphones.

Influence of smartphone use styles on typing performance and biomechanical exposure

Twenty-seven subjects completed 2-min typing tasks using four typing styles: right-hand holding/typing (S-thumb) and two-hand typing at three heights (B-low, B-mid and B-high). The styles had significant effects on typing performance, neck and elbow flexion and muscle activities of the right trapezius and several muscles of the right upper limb (p < 0.0001 by repeated-measure analysis of variance). The subjects typed the fewest words (error-adjusted characters per minute: 78) with the S-thumb style. S-thumb style resulted in similar flexion angles of the neck, elbow and wrist, but significantly increased muscle activities in all tested muscles compared with the B-mid style. Holding the phone high or low reduced the flexion angles of the neck and right elbow compared with the B-mid style, but the former styles increased the muscle activity of the right trapezius. Right-hand holding/typing was not a preferable posture due to high muscle activities and slow typing speed. Practitioner Summary: Right-hand holding/typing was not favoured, due to increased muscle activities and slower typing speed. Holding the phone high or low reduced the flexion angles of the neck and right elbow, but the former styles increased the muscle activity of the right trapezius compared with holding the phone at chest level.

Finger muscle attachments for an OpenSim upper-extremity model

We determined muscle attachment points for the index, middle, ring and little fingers in an OpenSim upper-extremity model. Attachment points were selected to match both experimentally measured locations and mechanical function (moment arms). Although experimental measurements of finger muscle attachments have been made, models differ from specimens in many respects such as bone segment ratio, joint kinematics and coordinate system. Likewise, moment arms are not available for all intrinsic finger muscles. Therefore, it was necessary to scale and translate muscle attachments from one experimental or model environment to another while preserving mechanical function. We used a two-step process. First, we estimated muscle function by calculating moment arms for all intrinsic and extrinsic muscles using the partial velocity method. Second, optimization using Simulated Annealing and Hooke-Jeeves algorithms found muscle-tendon paths that minimized root mean square (RMS) differences between experimental and modeled moment arms. The partial velocity method resulted in variance accounted for (VAF) between measured and calculated moment arms of 75.5% on average (range from 48.5% to 99.5%) for intrinsic and extrinsic index finger muscles where measured data were available. RMS error between experimental and optimized values was within one standard deviation (S.D) of measured moment arm (mean RMS error = 1.5 mm < measured S.D = 2.5 mm). Validation of both steps of the technique allowed for estimation of muscle attachment points for muscles whose moment arms have not been measured. Differences between modeled and experimentally measured muscle attachments, averaged over all finger joints, were less than 4.9 mm (within 7.1% of the average length of the muscle-tendon paths). The resulting non-proprietary musculoskeletal model of the human fingers could be useful for many applications, including better understanding of complex multi-touch and gestural movements.

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 = .0 I), slightly greater wrist extension in both hands (2 degrees to 3 degrees, 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.

Differences in typing forces, muscle activity, comfort, and typing performance among virtual, notebook, and desktop keyboards

The present study investigated whether there were physical exposure and typing productivity differences between a virtual keyboard with no tactile feedback and two conventional keyboards where key travel and tactile feedback are provided by mechanical switches under the keys. The key size and layout were same across all the keyboards. Typing forces; finger and shoulder muscle activity; self-reported comfort; and typing productivity were measured from 19 subjects while typing on a virtual (0 mm key travel), notebook (1.8 mm key travel), and desktop keyboard (4 mm key travel). When typing on the virtual keyboard, subjects typed with less force (p's < 0.0001) and had lower finger flexor/extensor muscle activity (p's < 0.05). However, the lower typing forces and finger muscle activity came at the expense of a 60% reduction in typing productivity (p < 0.0001), decreased self-reported comfort (p's < 0.0001), and a trend indicating an increase in shoulder muscle activity (p's < 0.10). Therefore, for long typing sessions or when typing productivity is at a premium, conventional keyboards with tactile feedback may be more suitable interface.

Hand usage pattern and upper body discomfort of desktop touchscreen users

A laboratory study was conducted to determine how users of different handedness interact with desktop touchscreen displays and how the hand usage pattern influences their body discomfort development. Twenty-one participants in three different handedness groups conducted simple web-browsing for 30 minutes using a 23″ touchscreen display while their subjective body discomfort, frequency of use of each hand and touch area preference were periodically quantified. Participants reported a gradual increase in body discomfort during web-browsing, and the increments in body discomfort varied between handedness groups for some body parts. Results also show that right-handed participants had stronger laterality than the left-handed, and ambidextrous participants used both hands more evenly than other participants, suggesting associations between the hand usage pattern and body discomfort development. Findings of the current study suggest that body discomfort of desktop touchscreen display users could be moderated by user-interface improvements and user training.

PRACTITIONER SUMMARY

Body discomfort development of desktop touchscreen users may be influenced by their hand usage pattern. Findings of this laboratory study suggest that user discomfort may be moderated by placing menu items in the lower area within the display or training users to alternate hands when conducting touch gestures.

Pain, Work-related Characteristics, and Psychosocial Factors among Computer Workers at a University Center

[Purpose] Complaint of pain is common in computer workers, encouraging the investigation of pain-related workplace factors. This study investigated the relationship among work-related characteristics, psychosocial factors, and pain among computer workers from a university center. [Subjects and Methods] Fifteen subjects (median age, 32.0 years; interquartile range, 26.8-34.5 years) were subjected to measurement of bioelectrical impedance; photogrammetry; workplace measurements; and pain complaint, quality of life, and motivation questionnaires. [Results] The low back was the most prevalent region of complaint (76.9%). The number of body regions for which subjects complained of pain was greater in the no rest breaks group, which also presented higher prevalences of neck (62.5%) and low back (100%) pain. There were also observed associations between neck complaint and quality of life; neck complaint and head protrusion; wrist complaint and shoulder angle; and use of a chair back and thoracic pain. [Conclusion] Complaint of pain was associated with no short rest breaks, no use of a chair back, poor quality of life, high head protrusion, and shoulder angle while using the mouse of a computer.

Touch displays: the effects of palm rejection technology on productivity, comfort, biomechanics and positioning

Direct touch displays can improve the human-computer experience and productivity; however, the higher hand locations may increase shoulder fatigue. Palm rejection (PR) technology may reduce shoulder loads by allowing the palms to rest on the display and increase productivity by registering the touched content and fingertips through the palms rather than shoulders. The effects of PR were evaluated by having participants perform touch tasks while posture and reaction force on the display were measured. Enabling PR, during which the subjects could place the palms on the display (but were not required to), resulted in increased wrist extension, force applied to the display and productivity, and less discomfort, but had no effect on the self-selected positioning of the display. Participants did not deliberately place their palms on the display; therefore, there was no reduction in shoulder load and the increased productivity was not due to improved hand registration. The increased productivity may have been due to reduced interruptions from palm contacts or reduced motor control demands.

Is the Ambidextrous Advantageous When using Large Touchscreens?

Conducting touch gestures on large format touchscreens for personal computers (PCs) is known to cause greater body discomforts than that from using a traditional PC due to frequent hand movements in floating arm postures. It was of interest whether the discomforts would vary depending on user’s handedness. The current study investigated potential associations between user’s handedness and subjectively assessed discomforts during the use of a 23” touchscreen personal computer. Twenty two participants were grouped by their handedness (left-handed, ambidextrous, right-handed), and conducted a typical web browsing task for 30 minutes while their hand/arm movements and subjective body discomfort ratings were periodically collected. Results show that ambidextrous participants used both hands more evenly than the other two groups, and they also reported significantly less body discomforts (p<0.05) compared to the others. To reduce physical discomforts and prevent musculoskeletal problems associated with the extended use of touchscreens, alternating hands in conducting touch gestures could be recommended.

Self-reported neck symptoms and use of personal computers, laptops and cell phones among Finns aged 18-65

The purpose of this study was to investigate the possible relation between self-reported neck symptoms (aches, pain or numbness) and use of computers/cell phones. The study was carried out as a cross-sectional study by posting a questionnaire to 15,000 working-age persons, and 15.1% of all respondents (6121) reported that they very often experienced physical symptoms in the neck. The results showed that they also had many other symptoms very often, and 49% used a computer daily at work and 83.9% used cell phones. We compared physical/mental symptoms of persons with symptoms in the neck quite often or more, with others. We found significant differences in the physical/mental symptoms and use of cell phones and computers. The results suggest taking into account in the future that those persons' symptoms in the neck can be associated with use of cell phones or computers.

PRACTITIONER SUMMARY

We investigated the possible relation between neck symptoms and use of computers/cell phones. We found that persons, who very often had symptoms in the neck, had also other symptoms very often (e.g. exhaustion at work). Their use of information and communication technology (e.g. computers) can associate with their symptoms.

Reactions, accuracy and response complexity of numerical typing on touch screens

Touch screens are popular nowadays as seen on public kiosks, industrial control panels and personal mobile devices. Numerical typing is one frequent task performed on touch screens, but this task on touch screen is subject to human errors and slow responses. This study aims to find innate differences of touch screens from standard physical keypads in the context of numerical typing by eliminating confounding issues. Effects of precise visual feedback and urgency of numerical typing were also investigated. The results showed that touch screens were as accurate as physical keyboards, but reactions were indeed executed slowly on touch screens as signified by both pre-motor reaction time and reaction time. Provision of precise visual feedback caused more errors, and the interaction between devices and urgency was not found on reaction time. To improve usability of touch screens, designers should focus more on reducing response complexity and be cautious about the use of visual feedback.

PRACTITIONER SUMMARY

The study revealed that slower responses on touch screens involved more complex human cognition to formulate motor responses. Attention should be given to designing precise visual feedback appropriately so that distractions or visual resource competitions can be avoided to improve human performance on touch screens.

Touch screen performance by individuals with and without motor control disabilities

Touch technology is becoming more prevalent as functionality improves and cost decreases. Therefore, it is important that this technology is accessible to users with diverse abilities. The objective of this study was to investigate the effects of button and gap size on performance by individuals with varied motor abilities. Participants with (n = 38) and without (n = 15) a motor control disability completed a digit entry task. Button size ranged from 10 to 30 mm and gap size was either 1 or 3 mm. Results indicated that as button size increased, there was a decrease in misses, errors, and time to complete tasks. Performance for the non-disabled group plateaued at button size 20 mm, with minimal, if any gains observed with larger button sizes. In comparison, the disabled group's performance continued to improve as button size increased. Gap size did not affect user performance. These results may help to improve accessibility of touch technology.

To twist, roll, stroke or poke? A study of input devices for menu navigation in the cockpit

Modern interfaces within the aircraft cockpit integrate many flight management system (FMS) functions into a single system. The success of a user's interaction with an interface depends upon the optimisation between the input device, tasks and environment within which the system is used. In this study, four input devices were evaluated using a range of Human Factors methods, in order to assess aspects of usability including task interaction times, error rates, workload, subjective usability and physical discomfort. The performance of the four input devices was compared using a holistic approach and the findings showed that no single input device produced consistently high performance scores across all of the variables evaluated. The touch screen produced the highest number of 'best' scores; however, discomfort ratings for this device were high, suggesting that it is not an ideal solution as both physical and cognitive aspects of performance must be accounted for in design.

PRACTITIONER SUMMARY

This study evaluated four input devices for control of a screen-based flight management system. A holistic approach was used to evaluate both cognitive and physical performance. Performance varied across the dependent variables and between the devices; however, the touch screen produced the largest number of 'best' scores.

Performance and touch characteristics of disabled and non-disabled participants during a reciprocal tapping task using touch screen technology

Touch screens are becoming more prevalent in everyday environments. Therefore, it is important that this technology is accessible to those with varying disabilities. The objective of the current study was to evaluate performance and touch characteristics (forces, impulses, and dwell times) of individuals with and without a movement disorder during a reciprocal tapping touch screen task. Thirty-seven participants with a motor control disability and 15 non-disabled participants participated. Outcome measures include number of correct taps, dwell time, exerted force, and impulse. Results indicate non-disabled participants had 1.8 more taps than participants with fine motor control disabilities and 2.8 times more than those with gross motor impairments (p<0.05). Additionally, people with gross motor control disabilities demonstrated longer dwell times and greater impulses (p<0.05). The average force used to activate the buttons was 6.2 N, although the button activation force was 0.98 N. Differences in reciprocal tapping and touch characteristics exist between those with and without motor control disabilities. Understanding how people (including those with disabilities) interact with touch screens may allow designers and engineers to ultimately improve usability of touch screen technology.

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.

Effect of touch screen button size and spacing on touch characteristics of users with and without disabilities

OBJECTIVE

The aim of this study was to investigate the effect of button size and spacing on touch characteristics (forces, impulses, and dwell times) during a digit entry touch screen task. A secondary objective was to investigate the effect of disability on touch characteristics.

BACKGROUND

Touch screens are common in public settings and workplaces. Although research has examined the effect of button size and spacing on performance, the effect on touch characteristics is unknown.

METHOD

A total of 52 participants (n = 23, fine motor control disability; n = 14, gross motor control disability; n = 15, no disability) completed a digit entry task. Button sizes varied from 10 mm to 30 mm, and button spacing was 1 mm or 3 mm.

RESULTS

Touch characteristics were significantly affected by button size. The exerted peak forces increased 17% between the largest and the smallest buttons, whereas impulses decreased 28%. Compared with the fine motor and nondisabled groups, the gross motor group had greater impulses (98% and 167%, respectively) and dwell times (60% and 129%, respectively). Peak forces were similar for all groups.

CONCLUSION

Button size but not spacing influenced touch characteristics during a digit entry task. The gross motor group had significantly greater dwell times and impulses than did the fine motor and nondisabled groups.

APPLICATION

Research on touch characteristics, in conjunction with that on user performance, can be used to guide human computer interface design strategies to improve accessibility of touch screen interfaces. Further research is needed to evaluate the effect of the exerted peak forces and impulses on user performance and fatigue.

The manipulability: a new index for quantifying movement capacities of upper extremity

In this work, it is proposed to evaluate the upper-limb movements through a global index of performance borrowed from the field of robotics: the manipulability. For a given posture, this index quantifies the set of velocities that can be achieved at the wrist in all the Cartesian directions. The manipulability can be represented by an ellipsoid from which the volume and shape related parameters can be derived. During a reach to grasp movement, the ellipsoid obtained from experiment presented a flattened shape along the forearm longitudinal axis and an increased volume as the arm was extended. From this study, it is concluded that: (1) the ellipsoid volume reflects well the ability to generate speed at the wrist which is effectively maximal for an extended posture; (2) if maximal velocity is an important parameter it might be advisable to primarily move the hand perpendicularly to the forearm longitudinal axis.

PRACTITIONER SUMMARY

The interest of manipulability indices is that they evaluate globally a posture of the upper-limb in relation to a given task. This original parameter could help to design environments or devices in order that the adopted postures maximise one particular aspect of the performance, i.e. the velocity of the hand.