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

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.

Smartphone addiction, musculoskeletal pain and functionality in university students - a observational study

Smartphone addiction and its excessive use could cause musculoskeletal symptoms such neck and upper limb pain. The purpose of this study was to investigate the association between smartphone use and musculoskeletal pain in the upper limbs and neck, as well as to observe the relationship in between smartphone addiction and musculoskeletal pain and upper limb function in university students. It is a cross-sectional, analytical study. A total of 165 university students participated in the research. Each student had their own smartphone. The students answered a structured questionnaire about pain in the upper limbs and neck; the Smartphone Addiction Inventory (SPAI) and the Disabilities of the Arm, Shoulder, and Hand questionnaire (DASH). Prevalence of neck and upper limb pain was 34.0%. Smartphone addiction and its use to play games and listen to music were risk factors to upper limb pain. Moreover, the smartphone addiction and age proved to be risk factors to neck pain. There was correlation between DASH and SPAI scores, and there was association between DASH score and neck and upper limb pain. Being of the female sex and smartphone addiction predicted the risk of incapacity development. We found association between neck and upper limb pain with smartphone addiction. Functional incapacity was associated to neck and upper limb pain. It was predicted by smartphone addiction and being of the female sex.

Defining text neck: a scoping review

BACKGROUND

Text neck is regarded as a global epidemic. Yet, there is a lack of consensus concerning the definitions of text neck which challenges researchers and clinicians alike.

PURPOSE

To investigate how text neck is defined in peer-reviewed articles.

METHODS

We conducted a scoping review to identify all articles using the terms "text neck" or "tech neck." Embase, Medline, CINAHL, PubMed and Web of Science were searched from inception to 30 April 2022. We followed the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews (PRISMAScR) guidelines. No limitation was applied for language or study design. Data extraction included study characteristics and the primary outcome relating to text neck definitions.

RESULTS

Forty-one articles were included. Text neck definitions varied across studies. The most frequent components of definitions were grouped into five basis for definition: Posture (n = 38; 92.7%), with qualifying adjectives meaning incorrect posture (n = 23; 56.1%) and posture without a qualifying adjective (n = 15; 36.6%); Overuse (n = 26; 63.4%); Mechanical stress or tensions (n = 17; 41.4%); Musculoskeletal symptoms (n = 15; 36.6%) and; Tissue damage (n = 7; 17.1%).

CONCLUSION

This study showed that posture is the defining characteristic of text neck in the academic literature. For research purposes, it seems that text neck is a habit of texting on the smartphone in a flexed neck position. Since there is no scientific evidence linking text neck with neck pain regardless of the definition used, adjectives like inappropriate or incorrect should be avoided when intended to qualify posture.

Lateral Elbow Pain and Muscle Function Impairments

Although often described as a self-limiting condition and likely to resolve on its own, high recurrence rates and extended sick leave frame a need for effective non-surgical treatment for people with lateral elbow tendinopathy. The interrelationship of histological and structural changes to the tendon, the associated impairments in motor control, and potential changes in pain processing may all drive symptoms. This clinical practice guideline covers the epidemiology, functional anatomy and pathophysiology, risk factors, clinical course, prognosis, differential diagnosis, tests and measures, and interventions for managing lateral elbow tendinopathy in the physical therapy clinic. J Orthop Sports Phys Ther 2022;52(12):CPG1-CPG111. doi:10.2519/jospt.2022.0302.

Typing with mobile devices: A comparison of upper limb and shoulder muscle activities, typing performance and perceived workload under varied body postures, typing styles and device types

This study aimed to examine the effects of body posture, typing style and device type on upper limb and shoulder muscle activities, typing performance and perceived workload while typing with mobile devices. Participants were asked to type with two mobile devices (i.e., a tablet and a smartphone) under three postures and in two typing styles. Muscle activity was recorded for four upper limb and shoulder muscles on both sides with surface electromyography. Results showed that body posture and typing style yielded significant effects on tying performance, perceived workload, and muscle activities in the forearm, upper arm and shoulder. Typing with a tablet was more accurate and had greater muscle activities in the upper arm and forearm on both sides than typing with a smartphone. The findings may be useful in developing evidence-based guidelines for the wise use of mobile devices and for the prevention of risks for musculoskeletal disorders.

Fatigue due to smartphone use? Investigating research trends and methods for analysing fatigue caused by extensive smartphone usage: A review

BACKGROUND: The easy accessibility of smartphones has led to a fivefold increase in their use. People use smartphones almost anywhere, including during travelling and studying. During the global COVID-19 pandemic, the average smartphone screen time has increased from 2.25 to 4.8 hours per day. In India, smartphone usage increased by 68%, and the average screen time increased from 2.42 to 6.9 hours. This dependency on smartphones has led to smartphone addiction. Inappropriate postures during the prolonged use of smartphones can exert adverse effects such as musculoskeletal disorders, digital eye strain, loss of focus and attention. OBJECTIVES: This study was undertaken to understand the effects of prolonged smartphone utilisation and explored fatigue measurement techniques. METHODS: A total of 130 studies examining the effects of smartphone utilisation published in the previous 10 years were identified from the following databases: IEEE, Science Direct, PubMed, PubMed Central, and Google Scholar are reviewed. This study was conducted from September 2019 to January 2021. RESULTS: One in every four adolescents were prone to smartphone addiction, which causes poor mental health. Moreover, India’s research on the effects of excessive smartphone usage is limited. CONCLUSIONS: Studies are required to establish the correlation between fatigue levels and smartphone usage patterns.

Differences in neck muscle activity according to lying positions using a smartphone

BACKGROUND

Due to the extended use of smartphones, people spend a lot of time on these devices while lying down.

OBJECTIVE

The purpose of the present study was to compare the differences in neck muscle activity of participants while they watched videos on a smartphone in four different lying positions (supine (SUP), prone on elbows (PE), side lying (SIDE), and 45∘ head turn while side lying (45-SIDE)).

METHODS

Twenty-three healthy volunteers (22.4 ± 1.7 years) were enrolled in this study. We assessed the activities of their right and left sternocleidomastoid (SCM), anterior scalene, cervical erector spinae (CES), and upper trapezius (UT) muscles while they watched videos on a smartphone in four different lying positions.

RESULTS

The right and left SCM and CES had significantly different muscle activities depending on the lying positions. The SCM activity had a significantly greater asymmetry in the 45-SIDE position, while the CES activity had a significantly greater asymmetry in the SIDE and 45-SIDE positions. Moreover, the UT activity had a significantly greater asymmetry in the SUP, PE, and SIDE positions.

CONCLUSIONS

Neck muscle activity and asymmetry were the lowest in the SUP position relative to the other positions. Therefore, lying down in the SUP position may minimize neck muscle activation while using a smartphone.

Development of an ergonomic design process for smartphone hard key locations

Smartphone hard key locations need to be ergonomically determined to improve grip stability and operational efficiency for users' convenience. The present study proposed an ergonomic design process that determines smartphone hard key locations by statistically analyzing the preferred hard key control areas of users with various hand sizes based on users' preferred grip postures and hard key control areas. The proposed design process analyzes the characteristics of product design, user, task, and use context, the types of preferred grip posture, the preference distribution of grip posture, and the preference distribution of hard-key area, and then recommends the locations of hard keys by considering the preference distribution of hard-key area and design constraints. The proposed design process was applied to a smartphone with a 5-inch screen, resulting in 77-96 mm from the bottom of the device for a volume key to 20 mm on the left side and 88-97 mm for a power key to 10 mm on the right side. The proposed design process for the determination of smartphone hard-key locations would be of use to determine the locations of various portable product interfaces.

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.

Influence of neck flexion angle on gravitational moment and neck muscle activity when using a smartphone while standing

This study compares the effects of different neck flexion angles on neck gravitational moment and muscle activity of users that stand and operate a smartphone. Thirty-two healthy young adult smartphone users performed texting tasks for three minutes at four different neck flexion angles (0°, 15°, 30°, and 45°) while standing. Neck gravitational moment and cervical erector spinae (CES) and upper trapezius (UT) activity were investigated. When the neck flexion angle increased, the gravitational moment of the neck increased significantly. The muscle activity of CES significantly increased when the neck flexion angle increased, whereas that of UT decreased. The lowest gravitational moment of the neck at 0° flexion was consistent with the lowest CES muscle activity and the lowest neck discomfort score. In conclusion, for texting while standing, adults should maintain their neck posture at 0° flexion to reduce the gravitational force acting on the cervical spine and alleviate neck discomfort. Practitioner Summary: During smartphone use when standing, excessive neck flexion (30° and 45° flexion) should be avoided. The suggested neck posture when operating a smartphone while standing is 0° flexion. Abbreviations: CES: cervical erector spinae; UT: upper trapezius; COG: centre of gravity; MSDs: musculoskeletal disorders; CROM: cervical range of motion; sEMG: surface electromyography; VAS: visual analogue scale; MVCs: maximum voluntary contractions.

Musculoskeletal symptoms among adult smartphone and tablet device users: a retrospective study

BACKGROUND

Previous literature suggests the use of smartphones and tablet devices may result in various postural and musculoskeletal disorders, predominantly of the neck and upper extremities. However, factors that contribute to the symptoms have not been adequately explored.

METHODS

This study aimed to investigate the prevalence and patterns (e.g. types, sites and temporal distributions) of musculoskeletal symptoms among adult smartphone and tablet device users. It also investigated device usage in terms of usage time, postures adopted during use, operational methods and purposes of device use in order to explain the symptom occurrences. Participants from eastern states of Australia retrospectively reported device usage and symptoms in the preceding two-week period, via an online survey. Data was analysed using Chi-square [χ2] analysis to determine the relationships between categorical variables; Mann-Whitney U tests to compare two groups (e.g. smartphone-only users versus tablet users) where dependant variables were ordinal; independent samples t-tests if dependent variables were continuous and approximated a normal distribution; and Spearman's correlation analysis to assess the relationships between pairs of continuous or ordinal variables.

RESULTS

Of the 207 participants, 59.9% reported musculoskeletal symptoms during or after device use; for 64.5% of these, symptoms began within the first 30 min (mostly between 15 and 30 min) of commencing usage. No statistically significant differences were observed between smartphone-only users and tablet device users in proportions reporting symptoms during device use (χ2 = .350, N = 207, p = .554). The most prevalent symptom was stiffness. The most prevalent symptom occurred in the neck (18.1% in smartphone-only users and 19.3% in tablet device users). Tablet users who were 18-24 year-old and used their device for more than 30 min in each usage session more often experienced symptoms (82.4% prevalence) than those who used a device for 30 min or less (52.2%) (χ2 = 4.723, N = 63, p = .030).

CONCLUSION

These findings suggest that user age, duration and frequency of usage, and type of device are important factors to consider in the formation of evidence-based guidelines to reduce experiences of musculoskeletal symptoms among smartphone and tablet device users. If usage was capped at < 15 min, the majority of smartphone and tablet device users would avoid symptoms.

Musculoskeletal pain and risk factors associated with smartphone use in university students

Background:

Smartphone has become a very popular necessity among students. An individual has to look at their phone's small monitor and perform repetitive movements in an awkward posture for a prolonged duration.

Objectives:

To assess the prevalence of musculoskeletal pain and associated risk factors in university students because of smartphone usage.

Subjects and Methods:

A cross-sectional study was conducted with 2000 university students using a semi-structured questionnaire comprising demographic profile, smartphone usage characteristics, presence of musculoskeletal pain, and specific area of pain according to the body region.

Results:

Among the 2000 students, 44.05% reported musculoskeletal pain. The most common sites of pain were the neck (34.2%), thumb (17.45%), lower back (16.7%), and elbow (16.6%). There was an association between prevalence of musculoskeletal pain with the size of the smartphone (P = 0.005), the predominant purpose of smartphone usage (P = 0.002), position preferred while using smartphone (P = 0.000), and the level at which smartphone is held during usage (P = 0.05). Logistic regression analysis revealed that the strongest predictor of musculoskeletal pain was the size of the smartphone.

Conclusion:

The study reported that the prevalence of pain in smartphone users is high with common sites being neck, thumb, and lower back region. Also, the size of the smartphone had a significant association with musculoskeletal pain.

Effects of Smartphone Size and Hand Size on Grip Posture in One-Handed Hard Key Operations

Greater understanding of the grip postures preferred by users is needed for the ergonomic design of smartphone user interfaces. The present study identifies user-preferred grip postures by smartphone size and hand size in one-handed hard key operations. Grip postures of 45 participants were photographed while major smartphone tasks were simulated in standing with smartphone mockups of nine screen sizes (3.0″–7.0″). The grip postures were encoded by the locations (left side: L, right side: R, top: T, bottom: B, front: F, back: K) of a smartphone and the number of fingers at each contact location. Three grip postures (L3-R1-K1: 70.0%, L4-R1: 13.3%, L3-R1-T1: 12.0%) were found dominant and the distribution of grip posture changed by smartphone size and hand size—the larger the smartphone size or hand size, the higher the frequency of L3-R1-K1. The grip posture frequency distribution by smartphone size would be of use to determine the optimal locations of hard keys on a smartphone of a particular size.

Head forward flexion, lateral bending and viewing distance in smartphone users: A comparison between sitting and standing postures

BACKGROUND

Smartphones (SPs) are widely used by people of all age groups and genders. Users spend many hours per day on the SPs for different purposes, which imposes significant stress on their musculoskeletal system.

OBJECTIVES

This study explored head forward flexion, lateral bending angle, and viewing distance while working with a SP in sitting/standing postures and one-handed/two-handed grips. The users' performance as well as pain development were also investigated.

METHODS

Participants answered a questionnaire on pain experience before and after SP usage. Neck kinematics of 20 SP users were monitored by a motion analysis system while doing three tasks (typing, video watching, and reading) in sitting and standing postures. Performance was evaluated by number of typed words, amount of errors in typing, and total read words.

RESULTS

The results indicated a significant increase in pain complaints in neck and upper limbs after test completion. Working with SPs in sitting and standing postures were, respectively, associated with greater head forward flexion for watching and viewing distance for two-handed typing tasks. Higher left lateral bending values were measured for one-handed watching and reading tasks in standing posture. The performance measures were superior for two-handed grips in all conditions.

CONCLUSIONS

Overall, using SPs in sitting posture creates greater head forward flexion and lower lateral bending angles in all tasks and grip types. The findings of this study can be used to provide recommendations for SP users.

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 field study on spinal postures and postural variations during smartphone use among university students

This field study compared the real-time spinal movements and postural variations during smartphone-use versus non-use in university students. Ten males and eight females (mean age of 21.5 ± 2.6 years) participated, with similar daily phone use time between the two sexes. Five inertial motion sensors were attached to the cervical, thoracic and lumbar spinal regions, and kinematics was recorded for 3 h while participants went about their usual academic activities within the university campus. Significantly greater degrees of cervical and upper thoracic flexion were adopted during phone use versus non-use time (p < 0.01). There were also significantly greater frequency of postural variations (zero crossing per min) in all spinal regions in the sagittal plane (all p < 0.05), and in some of the movements in transverse and frontal planes comparing phone use vs non-use. The postural variables also showed some significant correlations with self-reported pre-existing neck and upper back pain scores.

A prospective longitudinal study of mobile touch screen device use and musculoskeletal symptoms and visual health in adolescents

This study aimed to examine prospective associations of mobile touch screen device (i.e. smartphone, tablet) use and patterns of use with musculoskeletal symptoms and visual health among adolescents. A representative sample of 1691 adolescents in Singapore (51% girls; 10-19 years) completed an online questionnaire at baseline and one-year follow-up. After adjusting for potential confounders, prospective associations were found between baseline smartphone use and follow-up neck/shoulder (OR = 1.61(95%CI = 1.06-2.44)) and low back (OR = 1.86(1.10-3.14)) symptoms; tablet use was also associated with neck/shoulder, low back and arms symptoms (OR = 1.33(1.04-1.71)to1.52(1.18-1.95)). No associations were observed between the duration of smartphone/tablet use and symptoms. Baseline patterns of use (bout length, certain types of activities, multitasking) were associated with follow-up musculoskeletal symptoms. Smartphone/tablet use was not related to visual outcomes (visual symptoms, wearing glasses/contact lenses, myopia) at follow-up. These findings suggest that patterns of smartphone/tablet use (though not the duration of use) can pose a prospective risk for musculoskeletal symptoms.

Prevalence of MSDs and Postural Risk Assessment in Floor Mopping Activity Through Subjective and Objective Measures

Background

Residential and commercial cleaning is a part of our daily routine to maintain sanitation around the environment. Health care of professionals involved in such cleaning activities has become a major concern all over the world. The present study investigates the risk of musculoskeletal disorders in professional cleaners involved in floor mopping tasks.

Methods

A cross-sectional study was performed on 132 mopping professionals using a modified Nordic questionnaire. The Pearson correlation test was implemented to study the association of perceived pain with work experience. The muscle strain and postural risk were evaluated by means of three-channel electromyography and real-time motion capture respectively of 15 professionals during floor mopping.

Results

Regarding musculoskeletal injuries, risk was reported majorly in the right hand, lower back, left wrist, right shoulder, left biceps, and right wrist of the workers. Work experience had a low negative association with MSDs in the left wrist, right wrist, right elbow, lower back, and right lower arm (p < 0.01). Surface EMG showed occurrence of higher muscle activity in upper trapezius and biceps brachii (BB) muscles of the dominant hand and flexor carpi radialis and BB muscles of the nondominant hand positioned at the upper and lower portion of the mop rod, respectively.

Conclusion

Ergonomic mediations should be executed to lessen the observed risk of musculoskeletal injuries in this professional group of workers.

Evaluating hand performance and strength in children with high rates of smartphone usage: an observational study

[Purpose] This study investigated the interaction effects between the levels of smartphone use and hand dominance on handgrip, pinch strengths, and functional hand performance in children. [Participants and Methods] A total of 60 children aged between 9 and 15 were assigned into two groups: Group A (high-frequency smartphone users) and Group B (low-frequency smartphone users). Use levels were determined according to the smartphone addiction scale-short version. A hand dynamometer and pinch gauge were used to measure handgrip and pinch strength respectively. Functions of the upper extremity and hand were scored using the Quick Disabilities of the Arm, Shoulder, and Hand questionnaire. [Results] Group A participants had reduced measurements in hand grip and pinch strength, especially in the dominant hand. However, Quick Disabilities of the Arm, Shoulder, and Hand scores indicated that hand function was decreased in the dominant hand whether the child was a high- or low-frequency smartphone user. [Conclusion] Results indicated that high levels of smartphone use diminished hand and pinch-grip strengths as well as and hand function. That is, hand and pinch-grip strengths were reduced in the dominant hands of high-frequency smartphone users. However, hand functions were affected in the dominant hands among both high and low-level smartphone users.

Cervical spine joint loading with neck flexion

Cervical spine flexion is a common posture for those using computers, tablets, and smartphones; the latter being dubbed 'text-neck' in recent years. Coincidentally, flexion has been flagged as a significant mechanical risk factor for the development of chronic neck pain. Unfortunately, few modelling endeavours have attempted to quantify the intervertebral joint loads throughout the cervical spine in flexion, while still accounting for muscular activation. Eight healthy male subjects undertook five trials beginning in a neutral posture, flexed to 45 degrees, and returned to a neutral posture. 3 D head-trunk angles and surface electromyography from 10 neck muscles (5 bilaterally) were used as inputs into an inverse dynamic cervical spine model based on a 50th percentile male to compute the compression and anteroposterior (AP) shear forces for this flexion task. In general, compression increases cranially to caudally throughout the cervical spine, but levels off at the C5-C6 level. Conversely, in a neutral posture, there is a constant 18 N of anterior shear at each joint level. Compression increased twofold throughout the cervical spine with flexion, whereas anterior shear increased fourfold in the upper cervical spine and dramatically decreased caudally. The dramatic change in joint kinetics provides some mechanical evidence for the role of posture and interplay with muscle activity in the development of chronic neck pain. Results from this study can reinforce the need for appropriate workstation and monitor configurations and support the increased loading hypothesised to occur in 'text neck' postures. Practitioner summary: The purpose of this investigation was to quantify the compression and shear forces in the neck in 45 degrees of flexion compared to neutral. Flexion increased compression throughout the cervical spine 1.6-fold compared to a neutral posture. In the upper cervical spine, AP-shear increased four-fold compared to neutral. Abbreviation: AP: anteroposterior.

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.

Mobile touch screen device use and associations with musculoskeletal symptoms and visual health in a nationally representative sample of Singaporean adolescents

This study aimed to describe contemporary technology use, especially smartphones and tablets (mobile touch screen devices), and examine associations with musculoskeletal symptoms and visual health among adolescents in Singapore. A representative sample of 1884 adolescents (50.4% girls) from grades primary 5 to post-secondary (10-18 years old), recruited from 13 schools, completed an online questionnaire in class. Total technology use was high, with smartphone duration being highest (mean = 264 [SD = 243] min/day). Patterns of use, including multitasking and bout length, were influenced by gender, school level, type of device and activities. Musculoskeletal discomfort and visual symptoms were commonly reported. After adjusting for potential confounders, more hours/day of smartphone use was associated with increased risk of neck/shoulders, upper back, arms and wrist/hand discomfort (OR = 1.04[95%CI = 1.01-1.07] to 1.07[1.03-1.10]) and visual symptoms (OR = 1.05[1.02-1.08]), but was associated with decreased odds of myopia (OR = 0.97[0.94-0.99]). No significant associations were found for tablet use. Practitioner Summary: 1884 adolescents in Singapore completed an in-depth questionnaire regarding their use of technology. The smartphone was the device with the highest usage, and greater smartphone use was associated with increased odds of musculoskeletal and visual symptoms. High use of smartphones has physical health implications for adolescents.

Musculoskeletal disorder and pain associated with smartphone use: A systematic review of biomechanical evidence

The number of smartphone users is growing dramatically. Using the smartphone frequently forces the users to adopt an awkward posture leading to an increased risk of musculoskeletal disorders and pain. The objective of this study is to conduct a systematic review of studies that assess the effect of smartphone use on musculoskeletal disorders and pain. A systematic literature search of AMED, CINAHL, PubMed, Proquest, ScienceDirect using specific keywords relating to smartphone, musculoskeletal disorders and pain was conducted. Reference lists of related papers were searched for additional studies. Methodological quality was assessed by two independent reviewers using the modified Downs and Black checklist. From 639 reports identified from electronic databases, 11 were eligible to include in the review. One paper was found from the list of references and added to the review. The quality scores were rated as moderate. The results show that muscle activity of upper trapezius, erector spinae and the neck extensor muscles are increased as well as head flexion angle, head tilt angle and forward head shifting which increased during the smartphone use. Also, smartphone use in a sitting position seems to cause more shift in head-neck angle than in a standing position. Smartphone usage may contribute to musculoskeletal disorders. The findings of the included papers should be interpreted carefully in light of the issues highlighted by the moderate-quality assessment scores.

Texting with touchscreen and keypad phones - A comparison of thumb kinematics, upper limb muscle activity, exertion, discomfort, and performance

This study aimed to compare thumb kinematics and upper limb muscle activity, and the influence of hand size, when texting on a keypad smartphone and a touchscreen smartphone. Furthermore, the study compared exertion, discomfort, and performance when texting on the two phones. The thumb kinematics were tracked using a 3D motion analysis system and muscle activity was registered in six upper limb muscles using surface electromyography in 19 participants. When texting on the touchscreen phone compared to the keypad phone thumb flexion (p = 0.008) and flexion/extension range of motion were smaller (p = 0.02), the thumb was on average less internally rotated (p = 0.02), and activity (50th and 90th percentile) of the thumb and forearm muscles was lower (p ≤ 0.05). The differences in thumb flexion were found only in the group with shorter hands and the differences in muscle activity was found only in the group with longer hands. These findings suggest there are differences in risks for developing musculoskeletal disorders during smartphone use with different key activation mechanisms and different hand sizes.

A preliminary study of the influence of sagittal plane neck alignment on mylohyoid activity during oropharyngeal swallowing: A surface electromyographic analysis

OBJECTIVE

Forward head posture lengthens mylohyoid muscles, but its impact on swallowing is unknown. This study determined the effect of sagittal plane neck alignment on surface electromyographic parameters from mylohyoid muscles during oropharyngeal swallowing in healthy, young women.

METHODS

Surface EMG over bilateral mylohyoid muscles was recorded in 10 female subjects (22-37 y, Mean = 30 (5.1)) for average peak amplitude (μV). Percent time to peak activity and duration [s] were recorded in three different sitting postures: habitual posture (HP), exaggerated forward head posture (FHP), and optimal posture (OP) with head positioned in alignment with the spine.

RESULTS

Paired t-tests revealed that HP produced lower mylohyoid average peak amplitude than the FHP or OP. OP had greater average percent time to peak mylohyoid activity than HP.

DISCUSSION

HP yielded the most efficient mylohyoid activity. Muscle activation during swallowing should be addressed when training young women about OP.

Spinal kinematics during smartphone texting - A comparison between young adults with and without chronic neck-shoulder pain

To advance our understanding about the association between smartphone use and chronic neck-shoulder pain, the objective of this study was to compare spinal kinematics between different text-entry methods in smartphone users with and without chronic neck-shoulder pain. Symptomatic (n = 19) and healthy participants (n = 18) were recruited and they performed three tasks: texting on a smartphone with one hand, with two hands, and typing on a desktop computer. Three-dimensional kinematics were examined in the cervical, thoracic and lumbar regions for each task. This study suggests that altered kinematics may be associated with pain since significantly increased angles of cervical right side flexion during smartphone texting and greater postural changes in cervical rotation were found during all text-entry tasks in the symptomatic group. Two-handed texting was associated with increased cervical flexion while one-handed texting was correlated with an asymmetric neck posture, indicating both text-entry methods are not favorable in terms of spinal postures.

Smartphone form factors: Effects of width and bottom bezel on touch performance, workload, and physical demand

This study aimed at investigating the effect of two smartphone form factors (width and bottom bezel) on touch behaviors with one-handed interaction. User experiments on tapping tasks were conducted for four widths (67, 70, 72, and 74 mm) and five bottom bezel levels (2.5, 5, 7.5, 10, and 12.5 mm). Task performance, electromyography, and subjective workload data were collected to examine the touch behavior. The success rate and task completion time were collected as task performance measures. The NASA-TLX method was used to observe the subjective workload. The electromyogram signals of two thumb muscles, namely the first dorsal interosseous and abductor pollicis brevis, were observed. The task performances deteriorated with increasing width level. The subjective workload and electromyography data showed similar patterns with the task performances. The task performances of the bottom bezel devices were analyzed by using three different evaluation criteria. The results from these criteria indicated that tasks became increasingly difficult as the bottom bezel level decreased. The results of this study provide insights into the optimal range of smartphone form factors for one-handed interaction, which could contribute to the design of new smartphones.

Cumulative IT Use Is Associated with Psychosocial Stress Factors and Musculoskeletal Symptoms

This study aimed to examine the relationship between cumulative use of electronic devices and musculoskeletal symptoms. Smartphones and tablet computers are very popular and people may own or operate several devices at the same time. High prevalence rates of musculoskeletal symptoms associated with intensive computer use have been reported. However, research focusing on mobile devices is only just emerging in recent years. In this study, 285 persons participated including 140 males and 145 females (age range 18-50). The survey consisted of self-reported estimation of daily information technology (IT) exposure hours, tasks performed, psychosocial stress factors and relationship to musculoskeletal discomfort in the past 12 months. Total IT exposure time was an average of 7.38 h (±5.2) per day. The psychosocial factor of "working through pain" showed the most significant association with odds ratio (OR) ranging from 1.078 (95% CI = 1.021-1.138) for elbow discomfort, to 1.111 (95% CI = 1.046-1.180) for shoulder discomfort. Desktop time was also significantly associated with wrist/hand discomfort (OR = 1.103). These findings indicate only a modest relationship but one that is statistically significant with accounting for confounders. It is anticipated that prevalence rates of musculoskeletal disorders would rise in the future with increasing contribution due to psychosocial stress factors.

Effects of touchscreen gesture's type and direction on finger-touch input performance and subjective ratings

This study examined how finger-touch input performance (i.e. task completion time, failure status, and error rate) and subjective ratings (i.e. performance and physical demand) are influenced by touchscreen gestures' type and direction. Twenty participants performed one-touch (i.e. drag and swipe) and two-touch (i.e. pinch and spread) gesture tasks on a tablet, using several major directions (i.e. eight directions for one-touch and four directions for two-touch gestures). The results showed that swipe was approximately 4.5 times faster than drag, but pinch and spread showed no significant difference in task completion time. Dragging and pinching showed more failures or higher error rates compared to swiping and spreading, respectively. One-touch gestures in the horizontal directions were rated to have higher performance and lower physical demand than those in the vertical and diagonal directions. Two-touch gestures in the horizontal directions took the shortest time but caused more failures and higher error rates. Practitioner Summary: This study provides evidence for the effects of touchscreen gestures' type and direction on human performance and subjective ratings, which varied depending on the number of fingers used. Designers should arrange related touchscreen components accordingly, to improve touch-finger input performance and reduce user workload.

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.

Effects of Shoulder Taping on Discomfort and Electromyographic Responses of the Neck While Texting on a Touchscreen Smartphone

Background

Prolonged neck flexion during smartphone use is known as a factor of neck pain and alteration of neck muscle activity. Studies on the effects of shoulder taping on neck discomfort and neck muscle responses while texting on a smartphone are still lacking. The aim of this study was to examine the effects of shoulder taping on neck discomfort using a numerical rating scale, and neck muscle activity and fatigue using a surface electromyography during a texting task on a touchscreen smartphone.

Methods

Twenty-five healthy adolescents used the dominant hand to perform a 30-minute texting task using a touchscreen smartphone at two separate times under one of the following two conditions: taping across the upper trapezius muscle and no taping. Neck discomfort, normalized root mean square, and normalized median frequency slopes for upper trapezius, cervical erector spinae, and sternocleidomastoid muscles were recorded.

Results

The results revealed that shoulder taping provided significantly lower neck discomfort than no taping (p < 0.001). However, shoulder taping did not significantly alter normalized root mean square and normalized median frequency slope values of all muscles when compared with no taping controls.

Conclusion

Shoulder taping reduces neck discomfort but does not affect neck muscle activity and fatigue while texting on a touchscreen smartphone.

Fingertip forces and completion time for index finger and thumb touchscreen gestures

Users actuate touchscreen computers by applying forces with their fingers to the touchscreen, although the amount and direction of the force is unknown. Our aim was to characterize the magnitude, direction and impulse of the force applied during single finger (tapping and sliding in four directions) and two finger gestures (stretch and pinch). Thirteen subjects performed repeated trials of each gesture. Mean(±SD) resultant force was 0.50(0.09)N for tap, 0.79(0.32)N to 1.18(0.47)N for sliding gestures, 1.47(0.63)N for pinch and 2.05(1.13)N for stretch. Mean resultant force was significantly less (p<0.04) for tap than for all gestures except slide right. The direction of force application was more vertical for the two-finger gestures as compared to the single- finger gestures. Tap was the fastest gesture to complete at 133(83)ms, followed by slide right at 421(181)ms. On average, participants took the longest to complete the stretch gesture at 920(398)ms. Overall, there are differences in forces, force direction, and completion times among touchscreen gestures that could be used to estimate musculoskeletal exposure and help forge guidelines to reduce risk of musculoskeletal injury.

Prevalence and risk factors associated with musculoskeletal complaints among users of mobile handheld devices: A systematic review

This systematic review aimed at evaluating the prevalence and risk factors for musculoskeletal complaints associated with mobile handheld device use. Pubmed, Medline, Web of Science, CINAHL and Embase were searched. The methodological quality of included studies was assessed. Strength of evidence for risk factors was determined based on study designs, methodological quality and consistency of results. Five high-quality, eight acceptable-quality and two low-quality peer-reviewed articles were included. This review demonstrates that the prevalence of musculoskeletal complaints among mobile device users ranges from 1.0% to 67.8% and neck complaints have the highest prevalence rates ranging from 17.3% to 67.8%. This study also finds some evidence for neck flexion, frequency of phone calls, texting and gaming in relation to musculoskeletal complaints among mobile device users. Inconclusive evidence is shown for other risk factors such as duration of use and human-device interaction techniques due to inconsistent results or a limited number of studies.

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.

The influence of seat height, trunk inclination and hip posture on the activity of the superior trapezius and longissimus

[Purpose] This study was aimed at investigating the influence of seat height and body posture on the activity of the superior trapezius and longissimus muscles. [Subjects and Methods] Twenty two healthy subjects were instructed to perform a total of eight different body postures, varying according three main factors: seat height (low and high seat); trunk inclination (upright and leaning forward at 45°); and the hips in abduction and adduction. Electromyography of the superior trapezius and longissimus was collected bilaterally, and the average values were obtained and compared across all the postures. [Results] The activity of the superior trapezius and longissimus significantly changes according to the seat height and trunk inclination. For both seat heights, sitting with trunk leaning forward resulted in a significant increase in the activity of both muscles. When sitting in a high seat and the trunk leaning forward, the superior trapezius activity was significantly reduced when compared to the same posture in a low seat. [Conclusion] This study contributes to the knowledge on the influence of the body posture and seat configuration on the activity of postural muscles. Reducing the biomechanical loads on the postural muscles must be targeted in order to improve users’ comfort and safety.

Mobile Phone Use Behaviors and Postures on Public Transportation Systems

Mobile phones are common in our daily life, but the users’ preferences for postures or screen operating styles have not been studied. This was a cross-sectional and observational study. We randomly sampled passengers who used mobile phones on the Mass Rapid Transit (MRT) system in metropolitan Taipei. A checklist was used to observe their body postures and screen operating styles while sitting or standing. As a result, 1,230 subjects from 400 trips were observed. Overall, of all the passengers who were sitting, 41% of them were using mobile phones. The majority of the tasks involved browsing (84%) with their phones in a portrait orientation (93%). Different-hand holding/operating was the most commonly used operating style while sitting (46%) and same-hand holding/operating was the most common while standing (46%). The distribution of screen operating styles was significantly different for those sitting than for those standing and for different genders and age groups. The most frequently observed postures while sitting were having one’s trunk against a backrest, feet on the floor and with or without an arm supported (58%). As for the users who were standing, the both- and different-hands groups had a high proportion of arms unsupported, feet on the floor and either their trunk supported or not. In contrast, the same-hand group tended to have their trunk unsupported, were holding a pole or handstrap and had both feet on floor. Further studies are warranted to characterize the ergonomic exposure of these commonly used postures and operating styles, and our results will help guide the selection of experimental conditions for laboratory settings.