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Influence of smartphone use styles on typing performance and biomechanical exposure
Ergonomics
Abstract
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.
... The popularity of mobile devices has led to changes in the way people use electronic devices. Compared with desktop computers, mobile devices offer greater flexibility and convenience to users, as people may choose varied body postures and typing styles in the use of mobile devices (Ko et al., 2016;Liang and Hwang, 2016). It is common that people hold mobile devices with one or both hands in sitting, walking and reclining postures, and type with thumb or index fingers (Kietrys et al., 2015). ...
... While previous studies have adopted one or two tying styles in their experimental tasks, a few of studies have compared muscle activities, kinematics and musculoskeletal symptoms among different typing styles (Gustafsson et al., 2010(Gustafsson et al., , 2011Kietrys et al., 2015). For example, Ko et al. (2016) found that typing styles had significant effects on typing performance, neck and elbow flexion and muscle activities in the shoulder and upper limb. In particular, one-thumb typing was slower, and had increased muscle activities in shoulder and upper limb, compared with two-thumb typing. ...
... • The load would be greater for twohanded texting than for onehanded browsing. (Gustafsson et al., 2011(Gustafsson et al., , 2018Ko et al., 2016;Xie et al., 2016), larger mobile devices (e.g., tablets) that cannot be held for typing by one hand seems to be ignored. For larger mobile devices, index finger typing could be more appropriate. ...
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.
... There is no graphomotor component as typing/ tapping requires only the press of a button; the only difference between irrespective letters is their physical locations on the keyboard and the fingers used to press them. This involves much less muscle activity than writing and does not require fine motor control (Ko et al., 2015). Haptic feedback varies depending on the choice of keyboard and disappears altogether in the case of smartphones which have virtual keypads. ...
... Comparing Writing vs. Smartphone Tapping Speed addition, while tapping style impacted performance, keyboard typing skills (i.e., touch-typing ability) did not. Support for these findings can be found from an ergonomic perspective, as two-handed typing at chest level has been shown to activate the least muscle activity in the trapezius (the muscles which connect the shoulders and neck) and the fastest typing speed, with the slowest being single-hand thumb tapping (Ko et al., 2015). Interestingly, Palin et al., (2019) suggested that intelligent text entry methods of smartphones affected performance in various ways; autocorrection positively affected speed while word prediction actually hindered it. ...
... Smartphone tapping speed is an area that has still yet to be thoroughly investigated. While some studies have sought to measure the various speeds of different tapping styles or body positions (e.g., Ko et al., 2015;Palin et al., 2019), this is the first known study which examined how tapping speed compared to writing speed in participants' L1 versus an L2. To measure writing speeds without confounding variables such as creativity, lexical choice/knowledge, and spelling proficiency, graded passages were created for participants to transcribe, either by hand or by smartphone. ...
As COVID-19 pushes the world into emergency remote teaching mode, many teachers struggle with designing online or computer-mediated language learning activities due to having little to no prior experience. It is imperative to understand how the use of technology affects not only the processes of learning, but also the outcomes. Particularly in Japan, where smartphone ownership among adults aged 18-34 topped 96% in 2018 (Pew Research Center, 2019), many students use their phones to access their schools’ learning management systems (LMS) and complete assignments (i.e., mobile learning). The current study therefore sought to elucidate how different writing media can affect the execution of a simple writing task by examining the differences in transcription speeds between handwriting and ‘tapping’ on a smartphone. A total of 176 participants were divided into 3 groups (L1-English, writing in English; L1-Japanese, writing in Japanese; and L1-Japanese, writing in English), and their times-on-task were recorded. While no difference was found for the L1-English group, the L1-Japanese groups were found to be significantly faster at one task than the other (tapping in Japanese and writing in English). Pedagogical implications suggest the need for instructors to be aware of the extreme difficulty language learners may have when using mobile devices for writing tasks.
... All the invited subjects were right-handed and it may be interpreted that this was a compensatory behavior to bend their neck toward the non-dominate hand. A study conducted by Ko et al. showed that head flexion was similar in one-and two-handed grips [44]. However, they just focused on typing task. ...
... Comparison of number of typed words showed that the pace of tapping on touch screen with one thumb is lower than two thumbs. Previous studies demonstrated that in one-handed grip, right thumb needed to reach all the touchscreen, and access to further keys from base of thumb cause more pauses and as a result, number of typed words was lower [44,48]. Meanwhile, the result of the present study was in line with that of other studies which showed that holding an SP with the right hand and pressing buttons on the left side of the touchscreen was one of the main reasons for having misspellings [45,49]. ...
... Meanwhile, the result of the present study was in line with that of other studies which showed that holding an SP with the right hand and pressing buttons on the left side of the touchscreen was one of the main reasons for having misspellings [45,49]. In another study, right hand holding/typing was not favored, due to increased muscle activities and slower typing speed [44,50]. Having fully extension and flexion in thumb during one-handed grip is stated as another reason for a higher amount of errors in this task. ...
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 the musculoskeletal system.
Objectives:
This study explored head forward flexion, lateral bending angle, and viewing distance while working with an 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, reading) in sitting and standing postures. Performance was evaluated by number of typed words, amount of errors, and total read words in typing and reading.
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 an SP in a sitting posture creates greater head forward flexion and lower lateral bending in all tasks and grip types. The findings of this study can be used to provide recommendations for SP users.
... In view of RULA (second risk level) as well as the comfort zone described DIN 9241-303 these are to be regarded as critical. Ko et al. [20] measured the head tilt, depending on four different smartphone positions, while seated. If the phone was kept at eye level or in the lap, with the arms supported on the thighs and the trunk inclined, the neck was held without much flexion. ...
... Despite a neck flexion angle around zero the postures were not described as unproblematic because auf the trunk or the elbow flexion involved. For two other variations in smartphone position, Ko et al. [20] reported neck flexion angles around 20 • . Using mobile phones with keypads, Gustafsson et al. [21] detected a flexion below 20 • only for every seventh participant. ...
... In all seated conditions, like in the studies of Kietrys et al. [17] (smartphone, mini-tablet, and tablet) and Young et al. [25] (tablet) the activities found lay below 5% MVC. Equally for three out of four smartphone positions, Ko et al. [20] reported muscle activities lower than 5% MVC. However, holding the phone at about eye level while texting resulted in activities above 6% MVC. ...
Background:
Smart mobile devices gain increasing importance at work. Integrating these smart mobile devices into the workplace creates new opportunities and challenges for occupational health and safety.
Objectives:
Therefore the aim of the following scoping review was to identify ergonomic challenges with the use of smart mobile devices at work with respect to physical problems.
Method:
A review of 36 papers based on literature including January 2016 was conducted.
Results:
Biomechanical measures in the reviewed studies demonstrated i.e., head flexion angles exceeding 20° in 20 out of 26 different conditions described. Furthermore, laterally deviated wrists were frequently noted and thumb and finger flexor muscle activities generally greater than 5% MVC were reported.
Conclusion:
The reviewed literature indicated an elevated biomechanical risk, especially for the neck, the wrists and thumb. This was due to poor posture, ongoing and intermitted muscle tension, and/or repetitive movements. Papers addressing specific risks for smartphone and tablet use in different work environments are scarce. As the technology, as well as the use of smart mobile devices is rapidly changing, further research, especially for prolonged periods in the workplace is needed.
... Moreover, we assumed that people choose their operating styles based on comfort and performance. From the prospective of biomechanical loads, same-hand typing has a higher muscle load for the wrist extensors of the finger/thumb flexors than both-hands typing because of the increased effort needed for stability while holding the phone and operating it simultaneously [23][24][25]. It also rendered a slower texting speed [25]. ...
... From the prospective of biomechanical loads, same-hand typing has a higher muscle load for the wrist extensors of the finger/thumb flexors than both-hands typing because of the increased effort needed for stability while holding the phone and operating it simultaneously [23][24][25]. It also rendered a slower texting speed [25]. However, for people standing, it remained the preferred posture, possibly due to the need to use the other hand to carry things or hold poles/handstraps and the low demand on typing while browsing on the mobile phone. ...
... Our results revealed that more than 60% of the phone users had their upper limbs supported while sitting, especially in the both-hands group. The rationale was supported by the reduced muscle activities of the trapezius and biceps brachii for phone users with their elbows supported on their laps [25]. What was different from the designed posture in laboratory settings was that quite a few people had their elbows or wrists supported on their personal belongings on the MRT, instead of in their laps. ...
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.
... Smartphones, as ubiquitous communication and entertainment tools in people's daily life, have been widely used, and it has become an indispensable smart device to help people get information and engage in recreational activities quickly [1]. Because the smartphone needs to be held by hand while using, and people usually do not lift the phone to a position parallel to the line of sight of the human head, this directly increases the fatigue burden on the neck muscles [2][3][4][5]. In recent years, some studies also have shown a correlation between changes in the angle of the human head and neck comfort in the use of smartphones [3,[6][7][8]. ...
... Because the smartphone needs to be held by hand while using, and people usually do not lift the phone to a position parallel to the line of sight of the human head, this directly increases the fatigue burden on the neck muscles [2][3][4][5]. In recent years, some studies also have shown a correlation between changes in the angle of the human head and neck comfort in the use of smartphones [3,[6][7][8]. Lee et al. mentioned in the paper that changes in head posture have an important effect on pain caused by neck muscle pressure [9]. At the same time, several previous studies have shown that prolonged neck flexion due to the use of smartphones increases the likelihood of neck pain [5,6]. ...
Objectives:
The objective of this study was to explore the relationship between seat armrest height and human neck comfort when using a smartphone while sitting on a passenger seat during the flight.
Material and methods:
The authors used a wireless angle-measuring instrument and subjective comfort scale to evaluate the changes of head flexion angle and neck comfort level of 24 young smartphone users in an aircraft simulated cabin.
Results:
The study results indicated that using a smartphone while sitting on a passenger seat during the flight would pose a larger discomfort to the neck, and the discomfort would be higher for gaming than reading tasks. Seat armrest height is related to the comfort level of the neck when using a smartphone, increasing the height of the armrest can effectively alleviate discomfort in this state.
Conclusions:
Considering the prevalence of passengers using smartphones in aircraft, a seat armrest that can be properly adjusted in height, which can effectively reduce the risk of passenger head flexion angle and neck discomfort. Int J Occup Med Environ Health. 2022;35(2):199-208.
... If they were largely driven by an urge to reduce risk, they may hold the phone higher to reduce the viewing angle between the screen and the road. If they are primarily driven by their habit and biomechanical comfort, then we would expect them to demonstrate the same behavior as when seated, which typically involves a lower phone position and substantial neck flexion (Eitivipart et al., 2018;Ko et al., 2016). If the primary motivation is to avoid detection by law enforcement, then we might reasonably expect them to hold the phone lower to minimize the device visibility. ...
... Drivers appear to use their phones in a manner consistent with their regular seated behavior, phone held lower, with significant neck flexion (Ko et al., 2016), but largely by holding the wheel with their outside hand, regardless of handedness. The major contributor to phone-height, per Figure 5, was age, with older drivers more likely to hold the phone high. ...
Objective
Research shows frequent mobile phone use in vehicles but says little regarding how drivers hold their phone. This knowledge would inform countermeasures and benefit law enforcement in detecting phone use.
Methods
934 participants were surveyed over phone-use prevalence, handedness, traffic-direction, and where they held their device.
Results
The majority (66%) reported using their phone while driving. Younger drivers were more likely to use their device. Of device-users, 67% preferred their passenger-side hand, 25% driver-side, and 8% both. Height- wise: 22% held in-lap, 52% even with the wheel, and 22% at wheel-top. Older drivers were more likely to hold the phone in the highest position The three most popular combinations were passenger-middle (35%), passenger-low (19%), and passenger-high (13.9%). There was insufficient evidence of differences based on handedness, prevalence, or traffic-direction.
Conclusion
Driver-preferred attention regions often require substantial neck flexion and eye-movement, which facilitates distraction detection. However, behavior may change in response to future interventions.
... Moreover, with the development of electronic technology, many studies are now focused on investigating the effects of electronic devices on musculoskeletal load risk. Ko et al. [42] found using the right hand for one-handed typing produced greater muscle activity and predisposed the fingers to muscle fatigue and injury risk by measuring sEMG data for the upper trapezius (UT), biceps brachii (BB), common finger extensors (EDC), superficial finger flexors (FDS), and short thumb flexors (FPB). Onyebeke et al. [43] suggested that in the condition with a forearm-supported platform, there were fewer occurrences of forced postures of the wrist and smaller levels of activation of shoulder muscles.Alhaag et al. [44] used the response of myoelectric signals on the facial surface to investigate the effects of display type, viewing distance, and viewing time on visual fatigue and concluded that 3D displays produced less visual fatigue stress compared to 2D displays. ...
Recently Work-Related Musculoskeletal Disorders (WMSD) and Fatigue are taking on an important role especially in the progressive increase and tightening of the human-machine interface. Many ergonomists are currently using surface electromyographic (sEMG) signals techniques to investigate and assess muscle fatigue. Therefore, this paper provides a narrative review of current research on sEMG techniques in the field of human factors and ergonomic muscle fatigue.Evaluate and summarize studies related to the use of sEMG in human factors and ergonomics to probe muscle fatigue.Selected articles included publications in journals, books, and conference proceedings between 2012 and 2022 and assessed muscle activity in research using surface EMG techniques, intervention studies in real human subjects, quantitative research methods and evaluation tools, and authoritative study design.The final review included 32 articles and found that surface EMG studies in the field of human factors and ergonomic muscle fatigue mainly included risk assessment of work-related musculoskeletal disorders, workplace layout design assessment, usability assessment, and exoskeleton optimization assessment. Moreover, the current EMG experiments have significant variability in ideal and realistic conditions, and the lack of standardization of data and methods, which limits the development and application of EMG signals in human factors and ergonomic studies.The findings of this study can help ergonomists to understand the current research progress of sEMG techniques in this field in order to better select suitable, reliable, and accurate methods for human factors and ergonomic muscle fatigue assessment.
... In addition, data show that in the past few decades, the prevalence of neck pain among adolescents has constantly increased [4]. A survey of 140 college students shows that 98% of participants spend more than 3.5 hours on mobile phones every day, which increases the risk of neck disease [5]. The lifetime prevalence of neck pain among adults aged 20 to 69 was 66.7% [6]. ...
Objectives To provide reference for the evaluation and diagnosis of chronic neck pain (CNP) syndrome.
Methods 22 patients with CNP and 22 healthy people were recruited from South China Normal University, who were all college students. The subjects’ neck extensor muscle strength in head neutral position, natural anteversion position and maximum forward flexion position was measured by a tester for isometric muscle strength respectively. The static electromyography (EMG) of the subjects’ splenius capitis muscles and upper trapezius muscles was detected by a surface EMG device during isometric contractions of muscles, and the dynamic EMG of the subjects’ splenius capitis muscles and upper trapezius muscles was detected during head and neck flexion and extension. Neck extensor muscle strength, average electromyography (AEMG), integral electromyography (iEMG), rate of EMG contribution and flexion extension ratio (FER) in patients and healthy subjects were compared to find out electromyographic characteristics of neck muscles in college students with CNP.
Results (1) There were very significant differences in the maximum isometric muscle strength of neck extensor muscles between patients with CNP and healthy subjects in head neutral position, head natural forward position and head maximum flexion position (P < 0.001). (2) There were very significant differences in the average EMG of the neck muscle, which was isometrically contracted, between patients with CNP and healthy subjects in the head neutral position, head natural forward position, and head maximum flexion position (P < 0.001). (3) There were significant differences in the integral electromyography of the neck muscle, which was isometrically contracted, between patients with CNP and healthy subjects in the head neutral position, head natural forward position, and head maximum flexion position (P < 0.005). (4) In the head neutral position of patients with CNP and healthy people, the rates of integral electromyography contribution were respectively 51.5% and 53.9% (splenius capitis muscle)，and were respectively 48.4% and 45.3% (trapezius muscle) during an isometric contraction of neck muscles. In the natural anteversion position of the head，the values were respectively 49.1% and 54.0% (splenius capitis muscle)，and were respectively 50.8% and 45.9% (trapezius muscle). In the maximum anteflexion position of the head，the values were respectively 47.7% and 52.6% (splenius capitis muscle)，and were respectively 52.1% and 47.3% (trapezius muscle). (5) During neck muscles anteflexion of patients with CNP and healthy people，the averaged electromyography of splenius capitis muscles and trapezius muscles adds respectively up to 62.99 μv and 55.79 μv. There was a significant difference（P＜0.007）. During backward extension, the averaged electromyography adds respectively up to 64.75 μv and 79.22 μv. There was a significant difference ( P < 0.001 ). The flexion extension ratios of neck muscles in the two groups were respectively 0.95 and 0.62 on average. There was a significant difference（P＜0.001）.
Conclusions (1) Both neck extensor muscle strength and EMG level of college students with CNP were significantly lower than those of healthy college students. (2) Both splenius capitis muscles and trapezius muscles of college students with CNP had functional damage, and the functional damage of the former was severer. (3) During head and neck flexion and extension, FER of neck extensor muscle EMG in college students with CNP significantly increased, indicating that the active activity functions of neck extensor muscles of college students with CNP were insufficient and the flexion-relaxation responses were weakened.
... Therefore, occupational therapy in NEURO is recommended to provide more challenging exercises, such as those for adjusting the speed of joint movements, for complex movements that require multiple joints, and for resistance exercises. Regarding ADL, it is possible to aim to acquire activities that require hand dexterity and upper limb motor coordination, such as cooking, brushing teeth, operating smartphones and PCs, and putting on and taking off necklaces and earrings [65,66]. In addition, this can be expected to improve the quality of ADLs to a level desired by the patient. ...
Citation: Sakamoto, D.; Hamaguchi, T.; Murata, K.; Ito, H.; Nakayama, Y.; Abo, M. Upper Limb Function Recovery by Combined Repetitive Transcranial Magnetic Stimulation and Occupational Therapy in Patients with Chronic Stroke According to Paralysis Severity. Brain Sci. 2023, 13, 284. https://doi. Abstract: Repetitive transcranial magnetic stimulation (rTMS) with intensive occupational therapy improves upper limb motor paralysis and activities of daily living after stroke; however, the degree of improvement according to paralysis severity remains unverified. Target activities of daily living using upper limb functions can be established by predicting the amount of change after treatment for each paralysis severity level to further aid practice planning. We estimated post-treatment score changes for each severity level of motor paralysis (no, poor, limited, notable, and full), stratified according to Action Research Arm Test (ARAT) scores before combined rTMS and intensive occupational therapy. Motor paralysis severity was the fixed factor for the analysis of covariance; the delta (post-pre) of the scores was the dependent variable. Ordinal logistic regression analysis was used to compare changes in ARAT subscores according to paralysis severity before treatment. We implemented a longitudinal, prospective, interventional, uncontrolled, and multicenter cohort design and analyzed a dataset of 907 patients with stroke hemiplegia. The largest treatment-related changes were observed in the Limited recovery group for upper limb motor paralysis and the Full recovery group for quality-of-life activities using the paralyzed upper limb. These results will help predict treatment effects and determine exercises and goal movements for occupational therapy after rTMS.
... Therefore, occupational therapy in NEURO is recommended to provide more challenging exercises, such as those for adjusting the speed of joint movements, for complex movements that require multiple joints, and for resistance exercises. Regarding ADL, it is possible to aim to acquire activities that require hand dexterity and upper limb motor coordination, such as cooking, brushing teeth, operating smartphones and PCs, and putting on and taking off necklaces and earrings [65,66]. In addition, this can be expected to improve the quality of ADLs to a level desired by the patient. ...
Repetitive transcranial magnetic stimulation (rTMS) with intensive occupational therapy improves upper limb motor paralysis and activities of daily living after stroke; however, amount of improvement according to paralysis severity remains unverified. Target activities for daily living using patients’ upper limb functions can be established by predicting the amount of change after treatment for each severity level of upper limb motor paralysis and further aid practice planning. This study estimated post-treatment score changes for each severity level of motor paralysis (no, poor, limited, notable, and full) stratified according to Action Research Arm Test (ARAT) scores before combined rTMS and intensive occupational therapy. Severity of motor paralysis was the fixed factor for analysis of covariance, delta (post-pre) of the scores was the dependent variable. Ordinal logistic regression analysis was used to compare changes in ARAT subscores in patients, divided according to paralysis severity before treatment. A multicenter retrospective cohort dataset analyzed 907 patients with stroke hemiplegia. Largest treatment-related changes in scores were observed in the Limited recovery group for upper limb motor paralysis and Full recovery group for quality-of-life activities using paralyzed upper limb. These results will help predict treatment effects and determine exercises and goal movements for occupational therapy after rTMS.
... In the study by Xie et al. (2015), no significant differences were found in right and left upper trapezius muscles while working with SPs with one and twohands. Lee et al. (2015a) and Ko et al. (2016) found that one-handed grip operations on SP were associated with higher muscular activity in the upper trapezius. ...
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.
... Teknolojik cihaz kullanımı sırasındaki farklı tutma pozisyonları da kasiskelet sistemine etki etmektedir (P.-H. Ko, Hwang, & Liang, 2016;Young, Trudeau, Odell, Marinelli, & Dennerlein, 2013). Cihazların tek elle tutulması, iki elli tutmaya kıyasla bileklerde ve parmaklarda daha yüksek kas aktivitesine neden olmaktadır. ...
Günümüzde çocuklar hem geleneksel hem de modern teknolojiyle birlikte büyümektedirler. Televizyon, bilgisayar, cep telefonu ve tablet gibi teknolojik cihazların kullanım sıklığı her geçen gün daha da artmaktadır. Artan kullanım süresi ve sıklığı beraberinde birtakım sağlık sorunlarının ortaya çıkmasına sebep olmaktadır. Fiziksel aktivite düzeyinde azalma, obezite, kas-iskelet sistemi problemleri, uyku bozuklukları ve bağımlılık dijital teknoloji kullanımı ile ilişkili başlıca sağlık riskleridir. Bu bölümde, artan dijital teknoloji kullanımı sonucu karşılaşılabilecek sağlık problemleri özetlenmeye çalışılarak bu problemlerle başa çıkmaya yardımcı olacak bilgiler paylaşılmıştır.
... Smartphones have many apps and functions, such as games, internet access, and cameras for photos and videos. 1,2 These devices are produced annually in the order of millions, and a recent Brazilian study 3 predicted that by the end of 2017, Brazil would have one smartphone per inhabitant. ...
... Also, from previous studies when subjects with right hand dominance were many tasks in same time of using smartphones like writing, cooking, driving with calling or texting the static posture was taken by left side to carry and hold the smartphone during calling or texting but if no task performed with calling or texting most of subjects prefer to hold the smartphone by right dominant side during call and use bilateral hand texting. Right-hand holding/typing was not favored, due to increased muscle activities and slower typing speed [18]. ...
... The high portability of smartphones allows for their use in a great variability of postures. The optimal posture for smartphones use is not yet well established, but some studies findings provide information for users to keep the smartphone at eye level with a neutral spine postures, change their posture regularly, and reduce the time of smartphone use of possible [21][22][23]. ...
Purpose
The aim of the current study was to investigate the extent of smartphone use, possible correlation with neck pain and/or psychological impairment in office workers.
Method
A convenience sample of 1,602 office workers who were using smartphone for prolonged periods (≥ 4 years) participated in a cross-sectional report of a cohort study, assessing demographic, abnormal symptoms of pain in the neck, physical activity, and psychological behavior characteristics. Participants were assessed using a short version of the Smartphone Addiction Scale (SAS-SV), Depression, Anxiety and Stress Scales (DASS-42) questionnaire, as well as International Physical Activity Questionnaire-Short Form (IPAQ-SF). Multiple logistic regression model was conducted to evaluate the adjusted effect of smartphone overuse on nuchal symptoms.
Results
The prevalence of neck pain among the office workers was 30.1%. Significantly more female (33.3% vs. 24.5%) and younger (42.2 vs. 43.2 years) employees reported to have neck pain. Overall in 326 (20.3%, 95% CI: 18.4%–22.4%) of studied subjects had, SAS score ≥ 31 and ≥ 33 for male and females, respectively, and so smartphone overuse (SO) was diagnosed. The results of multiple logistic regression model revealed that those with SO were approximately 6 times more likely to have neck pain (95% CI: 4.44–8.09, P < 0.001).
Conclusions
Smartphone overuse in office workers significantly increases the chance of neck pain by 6 times. Hence SO has been associated with, not only somatic complaints, but also psychological distress such as anxiety, stress, and depression. This may necessitate adherence to neck-school, when smartphone use is associated with neck pain.
... Explore possible options for placing smartphones at the ideal height, especially when watching movies, webinars, and listening to educational content. Reduce single hand-holding and typing activities as it produces increased muscle activity [25]. ...
COVID-19 pandemic resulted in social mobility and travel restrictions to contain the infection. It has been reported
that there happened post-pandemic surge in the use of the internet and social media as people rely on it more often
for entertainment, work, and learning purposes. It is also being used as an unhealthy coping strategy for pandemic
related stress. The smartphone was found to be the most common gadget used for accessing internet-based
services. Owing to the postural alterations related to smartphones' small screen size, neck pain was reported very
commonly among smartphone users. Neck pain among smartphone users is a public health concern needing
immediate attention in the pandemic time. Many of the risk factors leading to neck pain among smartphone users are
modifiable. The authors outline preventive strategies that are mostly self- regulated. The strategies recommended
include reducing Smartphone usage time (Smartphone-Free Time, Smartphone-Free Zone), maintaining ideal
posture (Focus Breaks, Mobility Breaks, How am I keeping my posture?, Hands-free alternatives), doing regular
exercises, preparing and following an activity schedule, and inculcating healthy habits.
... O ver the last decade, the use of mobile phones has changed drastically with the advent of more technologically advanced smartphones. 1 Mobile phones are no longer used primarily as devices for talking but rather for text messaging, reading the news, drafting emails, browsing websites, and connecting with others on social media. Considering the increased utility and popularity of social media along with the greater reliance on smartphones, individuals in the United States and worldwide are undoubtedly spending more time on their handheld devices. 2 With the increase in use and overuse of smartphones, many aspects of society and health are likely affected. ...
As smartphones continue to gain popularity, skin changes to the fifth digit caused by extended use of these devices will become more prevalent. A 20-item survey was designed to assess smartphone use and skin changes that may be associated with smartphone use. This study is an initial step in uncovering a possible phenomenon of smartphone use affecting the digits, namely the fifth digit.
... Repetitiveness and prolonged gripping while texting cause hand pain-a phenomenon so prevalent among BlackBerry users that that condition was accorded its own term, that is, "BlackBerry thumb" (or hand) [29,30]. Finger and wrist positions influence deformity in the median nerve, which causes numbness and clumsiness in hand movements involved in daily routines [12,[31][32][33]. The SP-related neck pain known as text neck syndrome is a result of maintained and awkward posture while texting, especially when a user is holding a heavy SP for a long period as his/her neck is flexed [2,34]. ...
... Intensive electronic device users who assume a fixed posture for a long term are prone to developing exhaustion and neck and shoulder pain [9]. The activity of the upper trapezius was significantly associated with neck and elbow flexion angles while using the cellphones [10]. In addition, upper trapezius fatigue became more serious during neck flexion of 0°to 50° [11]. ...
Background
Neck and shoulder complaints caused by poor posture may influence upper trapezius stiffness. The relationship between the shear elastic modulus of the upper trapezius and cervical flexion angles is unknown. Therefore, it is essential to assess upper trapezius stiffness during cervical flexion. The objectives of this study were to (1) determine the intra- and interoperator reliabilities of evaluating upper trapezius stiffness and calculate the minimal detectable change (MDC); (2) examine the elastic modulus alterations of the upper trapezius during cervical flexion; and (3) explore the difference of upper trapezius stiffness between the dominant and nondominant sides.
Methods
Twenty healthy male participants were recruited in this study. The shear modulus of the upper trapezius was evaluated by two independent investigators using shear wave elastography (SWE) during cervical flexion at 0° and 50°.
Findings
The intraoperator (intraclass correlation coefficient (ICC) = 0.85–0.86) and interoperator (ICC = 0.94–0.98) reliabilities for measuring the shear elastic modulus of the upper trapezius during the cervical flexion ranged from good to excellent. An increase of 35.58% in upper trapezius stiffness was found at 0° to 50° of cervical flexion, and the MDC was 7.04 kPa. In addition, a significant difference was obtained in the elastic modulus of the upper trapezius muscle between the dominant and nondominant sides (P < 0.05).
Conclusions
Our findings revealed that SWE could quantify the elastic modulus of the upper trapezius and monitor its changes. Therefore, further studies are required to delineate the modulation in upper trapezius muscle stiffness among subjects with neck and shoulder pain.
... Of the students, 407 (77.97%) indicated typing in a nonrecommended way, which is when they were using both hands to hold the smartphone and typing on the screen only with their thumbs. Ko et al. 38 recommend holding the smartphone with just one hand and typing with the other hand using the index finger and avoiding using only the thumbs. In our data, only 1.53% of those who reported holding the device with the right hand and typing with the left and 3.07% of those holding with the left hand and typing with the right were doing so as recommended by the researchers. ...
Background:
Smartphones offer a variety of mobile applications for diverse purposes and access to services that contribute to an increased time of interaction with the device, influencing the users' health and behavior.Introduction: The time of interaction with smartphones is more intense with the younger generation, and physical, psychological, and social complications are reported. This research aims at identifying the factors associated with musculoskeletal symptoms due to the use of smartphones in university students in Brazil.Materials and Methods: The study has a quantitative transversal type approach, with 522 college students between the ages 18 and 26. A structured questionnaire was applied in 2017, to characterize the sociodemographic profile, composed of information regarding the use of smartphones added to the Nordic questionnaire of musculoskeletal symptoms.Results: One of the main results found was a tendency for participants to have symptoms of musculoskeletal pain with regards to their typing methods on smartphones. When asked about the cases when such symptoms were considered to be related to the use of the device, most cited the cervical region (43.87% of cases). It was also found that those who type on their phones with the head at 45° and 60° angles are about twice as likely to have higher scores of severe symptoms than those typing with their neck at 0° (anatomical position).Conclusion: Within the university student population the typing position on a smartphone and time of use are associated with the presence of pain in the cervical region.
... Sitting and standing are typical working postures in different workstation settings. Prior research found the posture effect on task performance when people use physical keyboards, computers, trackballs and touchscreens (Ghesmaty, Gustafson, and Cavuoto 2016;Liao and Drury 2000;Kar and Hedge 2016;Ko, Hwang, and Liang 2016;Schedlbauer, Pastel, and Heines 2006). Difference in muscle activity was found between sitting and standing when people use computers (Lehman, Psihogios, and Meulenbroek 2001;O'Sullivan et al. 2002). ...
This study aimed to determine the touch characteristics during tapping tasks on membrane touch interface and investigate the effects of posture and gender on touch characteristics variables. One hundred participants tapped digits displayed on a membrane touch interface on sitting and standing positions using all fingers of the dominant hand. Touch characteristics measures included average force, contact area, and dwell time. Across fingers and postures, males exerted larger force and contact area than females, but similar dwell time. Across genders and postures, thumb exerted the largest force and the force of the other four fingers showed no significant difference. The contact area of the thumb was the largest, whereas that of the little finger was the smallest; the dwell time of the thumb was the longest, whereas that of the middle finger was the shortest. Relationships among finger sizes, gender, posture and touch characteristics were proposed. The findings helped direct membrane touch interface design for digital and numerical control products from hardware and software perspectives.
Practitioner Summary: This study measured force, contact area, and dwell time in tapping tasks on membrane touch interface and examined effects of gender and posture on force, contact area, and dwell time. The findings will direct membrane touch interface design for digital and numerical control products from hardware and software perspectives.
... This may be related to differences in tactile feedback and visual demands. Since the touchscreen phone do not provide tactile feedback (Hoggen et al., 2008), the users may either lift the phone or bend their head forward in order to get visual feedback which may result in a higher muscle activity in the trapezius muscle (Ko et al., 2016;Lee et al., 2015;Straker et al., 2008a). ...
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 exer-tion, 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 electro-myography 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.
... The user interface (UI) affects biomechanics and motor performance for both gestures. Studies have explored how upper extremity biomechanics and performance are affected by factors such as touch target size and location during tapping tasks (Park & Han, 2010;Ko, Hwang, & Liang, 2016;Jeong & Liu, 2017). In addition, Jeong & Liu (2017) found horizontal swipes using the index finger had better self-reported performance and lower physical demands than vertical swipes. ...
Tablet computers' hardware and software designs may affect upper extremity muscle activity and postures. This study investigated the hypothesis that forearm muscle activity as well as wrist and thumb postures differ during simple gestures across different tablet form factors and touchscreen locations. Sixteen adult (8 female, 8 male) participants completed 320 tablet gestures across four swipe locations, with various tablet sizes (8″ and 10"), tablet orientations (portrait and landscape), swipe orientations (vertical and horizontal), and swipe directions (medial and radial). Three-dimensional motion analysis and surface electromyography measured wrist and thumb postures and forearm muscle activity, respectively. Postures and muscle activity varied significantly across the four swipe locations (p < .0001). Overall, swipe location closest to the palm allowed users to swipe with a more neutral thumb and wrist posture and required less forearm muscle activity. Greater thumb extension and abduction along with greater wrist extension and ulnar deviation was required to reach the target as the target moved farther from the palm. Extensor Carpi Radialis, Extensor Carpi Ulnaris, Flexor Carpi Ulnaris, Extensor Policis Brevis, and Abductor Pollicis Longus muscle activity also increased significantly with greater thumb reach (p < 001). Larger tablet size induced greater Extensor Carpi Radialis, Extensor Carpi Ulnaris, Flexor Carpi Ulnaris, Flexor Carpi Radialis, and Abductor Pollicis Longus muscle activity (p < .0001). The study results demonstrate the importance of swipe locations and suggest that the tablet interface design can be improved to induce more neutral thumb and wrist posture along with lower forearm muscle load.
... Different MTSD handhold positions were examined in one case-control and some experimental laboratory studies. One experimental laboratory study found significantly higher neck and elbow flexion while handholding a smartphone at chest level, compared to at eye or knee level (with the trunk bent forward and elbows resting on the thighs) [49]. Muscle activity of the upper trapezius muscle was, however, significantly higher at eye level than at knee and chest level. ...
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.
... Recent studies showed that smartphone operation with 1 hand caused greater upper trapezius pain and induced increased upper extremity muscle activity than operation with both hands. 40,41 A study by _ Inal and colleagues 7 also showed enlargement of the median nerve in highly active smartphone users who have a habit of single-handheld smartphone use. They further demonstrated that not only the median nerve but also tendons were significantly larger in the dominant hand of smartphone users than in the dominant hand of nonusers. ...
Introduction:
This study investigates the results of a questionnaire, provocative tests, and ultrasonographic measurements of carpal tunnel morphological parameters in intensive and nonintensive electronic device users.
Methods:
Forty-eight university students (equal numbers of intensive and nonintensive users, ≥5 h/day and <5 h/day of electronic device usage, respectively) were randomly selected after questionnaire responses were received and evaluated clinically and by ultrasonography. All participants were right-handed.
Results:
Intensive users had significantly more positive results in Phalen's and Durkan's tests and reported more wrist/hand pain compared with nonintensive users (P < 0.05). Intensive users also had significantly larger median nerve cross-sectional areas, flattening ratios, and perimeters as well as greater bowing of the transverse carpal ligament compared with nonintensive users (P < 0.05).
Discussion:
Overuse of electronic devices may adversely affect the median nerve within the carpal tunnel and the transverse carpal ligament, resulting in numbness, tingling, and pain in the hand. Caution may be warranted when using handheld electronic devices. Muscle Nerve, 2017.
Background
In recent years, smartphones have become popular worldwide and are used in daily life. Consequently, the musculoskeletal discomfort associated with smartphone use has become a problem. Neck pain, also known as text neck syndrome, develops due to neck flexion posture.
Objective
The present study determined how the neck flexion angle increases with the difficulty of a task performed on a smartphone. This study also assessed the factors associated with the neck flexion angle while using a smartphone.
Methods
Subjects were 24 healthy adults. Using the VICON motion analysis system, neck flexion angles while using a smartphone were measured under three conditions: normal standing (control), standing while watching a video (watching), and standing while typing (typing).
Results
The neck flexion angles (mean ± standard deviation) were 0.71 ± 7.05° for the control, 26.02 ± 6.28° for watching, and 30.52 ± 7.83° for typing, indicating a significant difference (p < 0.001). Significant differences were also observed between the control-watching, control-typing, and watching-typing conditions (p < 0.001). A correlation was found between average daily smartphone usage time and the neck flexion angle of typing (r = 0.531, p = 0.008).
Conclusions
The neck flexion angle increased with the difficulty of the task performed on the smartphone. People with a longer average daily smartphone usage time were more likely to adopt a neck flexion posture while using their smartphones than those with a shorter average usage.
Background
Posture during smartphone use is an important factor that affects musculoskeletal pain.
Objective
To investigate the prevalence and characteristics of musculoskeletal pain in the neck, trunk, and upper extremities during smartphone use.
Methods
A total of 326 Chinese and Korean smartphone users participated in an online survey on smartphone posture, addiction, and musculoskeletal pain.
Results
The neck, shoulder, and lower back were most frequently affected, whereas the elbow, lower back, and forearm showed the highest level of discomfort. Stiffness was the predominant type of discomfort in most body parts. Numbness surpassed stiffness in the elbow and hand, whereas throbbing surpassed stiffness in the wrist. Body posture influenced upper arm and lower back discomfort, with a right-sided lying posture resulting in the highest level of lower back pain (p < 0.05). Using a smartphone with a more flexed neck posture increased neck discomfort (p < 0.05). Holding a smartphone with one hand, while controlling the screen with the opposite finger, increased hand pain (p < 0.05).
Conclusion
The inferences obtained from this study indicate that smartphone usage posture significantly affects musculoskeletal discomfort. The suggested posture for minimizing musculoskeletal discomfort is to use the smartphone in a left-side-lying position, hold it vertically with both hands, and utilize both thumbs for texting and scrolling.
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.
OCCUPATIONAL APPLICATIONS
The National Occupational Research Agenda for Musculoskeletal Health in the United States identified that with the changing nature of the traditional office environment, mobile devices are now frequently used for longer durations, warranting research on the impacts of mobile computing on musculoskeletal health. A recent study of office workers showed that those with “smartphone overuse” were six times more likely to report neck pain. Working in pain may also result in withdrawal and less proactive extra-role behaviors at work (such as making recommendations at work and willing to help colleagues). We found that 30-minutes of mobile device use resulted in pain reporting in the neck and upper back when the device was used with neck flexion. This musculoskeletal pain could lead to acute concerns during the workday and long-term problems over time.
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.
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.
Smartphones are currently among the most common handheld devices. Previous studies on such handheld touchscreen devices focused on thumb operations or reach zones by measuring individual muscle or joint angles. However, they were limited to thumb operations and did not consider grasping. In this study, we investigated the grasp types of touchscreen devices and other objects included in an existing grasp taxonomy. To this end, principal component analysis and latent profile analysis clustering were used for extracting and grouping muscle and postural synergies. Fourteen healthy subjects performed up to 15 hand grasps, including that with a smartphone. Electromyography (EMG) data were measured on six muscles in the forearm and the hand, and joint angles were measured for 22 joints in the hand. The first two muscle synergies from the EMG data and the first three postural synergies from the kinematic data were found to account for over 60% of the overall grasping. In terms of the synergies, the grasp for handheld touchscreen devices showed unique characteristics in terms of muscle and postural synergies compared to other objects. The obtained results may aid in understanding of grasping behaviors for handheld touchscreen devices in various applications.
BACKGROUND: In 2020, the number of smartphone users worldwide projected to reach 3.5 billion and in India alone 374.8 million smartphone users. Most of the young adults spend an average of 3 to 4 hours daily. The extensive usage of smartphone increases risk of disorders, including cervical, shoulder pain, etc. OBJECTIVE: The motivation behind the investigation is twofold: examine the effects caused by prolonged usage of smartphone through extensive literature survey and discuss the methods available to analyze the head posture, and neck-muscle fatigue. METHODS: Various database were investigated for literature and restricting to recent ten years (2010-2019). The chosen keywords for the research were a combination of smartphone, head flexion angle, neck muscle activity, neck pain, head posture, biomedical instrumentation, and sensor technologies. RESULTS: Posture of head, including flexion/extension angle while using smartphone, and text neck syndrome received lot of attention among international researchers. Not many studies were found in India, though our population is more vulnerable to health risk. CONCLUSION: Research on extensive usage of smartphone and associated occupational health risks lack in India. Comprehensive and systematic work is required to understand the relationship between musculoskeletal disorders, and smartphone usage.
The purpose of this study was to explore whether virtual reality (VR) and augmented reality (AR) cervical somatosensory games can effectively alleviate neck discomfort caused by mobile phones. If validation was effective, the effect of VR and AR games on neck muscle fatigue alleviation was compared. Twenty-four healthy adults between ages 19 and 25 participated in the study. Experiment 1 was to verify the fatigue of neck and shoulder muscles caused by long-term use of mobile phones. Experiment 2 explored whether the VR game and the AR game have an impact on neck muscle fatigue and compared the degree of influence. The integrated electromyography (IEMG) and median frequency (MF) of the upper trapezius, splenius cervical muscles, and sternocleidomastoid muscles were collected. Experiment 1 showed that the MF of some muscles of the participants of both the VR group and the AR group decreased with time, while the IEMG of some muscles increased with time. Experiment 2 showed that the MF of some muscles of the participants of both the VR group and the AR group showed an upward trend, while the IEMG of some muscles showed a downward trend. There were significant differences between experiment 1 and experiment 2 (P < 0.05). The results of the subjective evaluation scale of neck muscle fatigue filled in by the participants were consistent with the experimental results, which showed that both the VR group and the AR group could feel the cervical relief, and the VR game could better alleviate the neck and shoulder muscle fatigue.
This paper concerns the design of optimized single-finger keyboard layouts on smartphones. In the literature, the optimization problem associated with assigning characters to keys on a single-finger keyboard is denoted as single-finger keyboard layout problem (SK-QAP), which can be seen as a variant of the quadratic assignment problem (QAP), a classical combinatorial optimization problem. To solve it, we propose a simple yet effective local search-based metaheuristic which is composed of three neighborhood structures. Two of them were previously applied to solve the SK-QAP, whereas the third one consists of an adaptation of a QAP neighborhood and it was introduced in this work. In addition, two perturbation mechanisms were developed as diversification procedures and together with the latter neighborhood structure, they revealed to be highly beneficial for improving the performance of the algorithm. Computational experiments were carried out on benchmark instances for English, French, Italian and Spanish. The results obtained were extremely competitive both in terms of solution quality and CPU time, such that all best known solutions were found in a matter of seconds. Moreover, we developed and solved benchmark instances for Portuguese, which currently has more than 230 million speakers, as a first or second language, and also uses the Latin alphabet. We have also proposed and solved bilingual instances, combining English, one of the top spoken languages in the world, with each of the remaining four ones. In addition, we quantify the potential practical benefits of adopting alternative and smartphone-oriented optimized single-finger keyboards, when compared to well-known layouts, namely QWERTY and AZERTY, for the five languages and bilingual variants considered. Finally, we show the efficiency of the proposed algorithm when generating layouts based on other existing arrangements, namely Metropolis and FITALY.
There are concerns about the safety of texting while walking. Although evidence of negative effects of mobile phone use on gait is scarce, cognitive distraction, altered mechanical demands, and the reduced visual field associated with texting are likely to have an impact. In 26 healthy individuals we examined the effect of mobile phone use on gait. Individuals walked at a comfortable pace in a straight line over a distance of ∼8.5 m while; 1) walking without the use of a phone, 2) reading text on a mobile phone, or 3) typing text on a mobile phone. Gait performance was evaluated using a three-dimensional movement analysis system. In comparison with normal waking, when participants read or wrote text messages they walked with: greater absolute lateral foot position from one stride to the next; slower speed; greater rotation range of motion (ROM) of the head with respect to global space; the head held in a flexed position; more in-phase motion of the thorax and head in all planes, less motion between thorax and head (neck ROM); and more tightly organized coordination in lateral flexion and rotation directions. While writing text, participants walked slower, deviated more from a straight line and used less neck ROM than reading text. Although the arms and head moved with the thorax to reduce relative motion of the phone and facilitate reading and texting, movement of the head in global space increased and this could negatively impact the balance system. Texting, and to a lesser extent reading, modify gait performance. Texting or reading on a mobile phone may pose an additional risk to safety for pedestrians navigating obstacles or crossing the road.
Unlabelled:
The purpose of this study was to evaluate tablet size (weight), orientation, grip shape, texture and stylus shape on productivity, biomechanics and subjective usability and fatigue when the tablet was held with just the left hand. A total of 15 male and 15 female subjects, ages 16-64 years, tested eight tablets and three styluses. Overall, the usability, fatigue and biomechanical evaluation of tablet design features supported the use of smaller to medium-sized tablets, with a ledge or handle shape on the back and surfaced with a rubberised texture. Larger, heavier tablets had significantly worse usability and biomechanics and their use with one hand should be limited. The stylus with a tapered grip (7.5-9.5 mm) or larger grip (7.6 mm) had better usability and biomechanics than one with a smaller grip (5 mm). There were no significant differences in productivity between design features. These design parameters may be important when designing tablets.
Practitioner summary:
Different tablet and stylus design features were evaluated for usability and biomechanical properties. On the basis of short-term tasks, emulating functional tablets, usability was improved with the smaller and medium-sized tablets, portrait (vs. landscape) orientation, a back ledge grip and rubberised texture. There were no differences in productivity between design features.
When holding a tablet computer with two hands, the touch keyboard configuration imposes postural constraints on the user because of the need to simultaneously hold the device and type with the thumbs. Designers have provided users with several possible keyboard configurations (device orientation, keyboard layout and location). However, potential differences in performance, usability and postures among these configurations have not been explored. We hypothesize that (1) the narrower standard keyboard layout in the portrait orientation leads to lower self-reported discomfort and less reach than the landscape orientation; (2) a split keyboard layout results in better overall outcomes compared to the standard layout; and (3) the conventional bottom keyboard location leads to the best outcomes overall compared to other locations. A repeated measures laboratory experiment of 12 tablet owners measured typing speed, discomfort, task difficulty, and thumb/wrist joint postures using an active marker system during typing tasks for different combinations of device orientation (portrait and landscape), keyboard layout (standard and split), and keyboard location (bottom, middle, top). The narrower standard keyboard with the device in the portrait orientation was associated with less discomfort (least squares mean (and S.E.) 2.9±0.6) than the landscape orientation (4.5±0.7). Additionally, the split keyboard decreased the amount of reaching required by the thumb in the landscape orientation as defined by a reduced range of motion and less MCP extension, which may have led to reduced discomfort (2.7±0.6) compared to the standard layout (4.5±0.7). However, typing speed was greater for the standard layout (127±5 char./min.) compared to the split layout (113±4 char./min.) regardless of device orientation and keyboard location. Usage guidelines and designers can incorporate these findings to optimize keyboard design parameters and form factors that promote user performance and usability for thumb interaction.
Background:
Due to its rapid growth in popularity, there is an imminent need for ergonomic evaluation of the touch-screen tablet computing form-factor.
Objective:
The aim of this study was to assess postures of the shoulders and wrists and their associated muscle activity during touch-screen tablet use.
Methods:
Fifteen experienced adult tablet users completed a set of simulated software tasks on two media tablets in a total of seven user configurations. Configurations consisted of a combination of a support condition (held with one hand, two hands or in a case), a location (on the lap or table surface), and a software task (web browsing, email, and game). Shoulder postures were measured by using an infra-red LED marker based motion analysis system, wrist postures by electro-goniometry, and shoulder (upper trapezius and anterior deltoid) and forearm (flexor carpi radialis, flexor carp ulnaris, and extensor radialis) muscle activity by surface electromyography.
Results:
Postures and muscle activity for the wrist significantly varied across configurations and between hands, but not across the two tablets tested. Wrist extension was high for all configurations and particularly for the dominant hand when a tablet was placed on the lap (mean=38°). Software tasks involving the virtual keyboard (e-mailing) corresponded to higher wrist extensor muscle activity (50th percentile=9.5% MVC) and wrist flexion/extension acceleration (mean=322°/s2). High levels of wrist radial deviation were observed for the non-dominant hand when it was used to tilt and hold the tablet (mean=13°). Observed differences in posture and muscle activity of the shoulder were driven by tablet location.
Conclusion:
Touch-screen tablet users are exposed to extreme wrist postures that are less neutral than other computing technologies and may be at greater risk of developing musculoskeletal symptoms. Tablets should be placed in cases or stands that adjust the tilt of the screen rather than supporting and tilting the tablet with only one hand.
The hypothesis of this study was that arthrodesis of the thumb interphalangeal joint at a degree of flexion greater than the recommended 0 degrees to 15 degrees in the era of widespread use of handheld devices would potentially be more beneficial for the use of these devices. For patients who rely heavily on a smart-phone or handheld device and require dominant thumb arthrodesis, thumb interphalangeal arthrodesis at an angle of 10 degrees or 30 degrees will neither improve nor impede their use of the device.
A relationship between m. trapezius load measured by electromyography (EMG) and the incidence of musculoskeletal illness in the neck and shoulder regions, was investigated both for assembly workers and VDT operators. For assembly workers, the static trapezius load (probability 0.1 of the amplitude probability distribution function, APDF) was significantly reduced from 4.3% MVC (Maximum Voluntary Contraction) to 1.4% MVC as a group median value after an ergonomic adaptation of their work places. Musculoskeletal sickleave was significantly reduced from 22.9 days to 1.8 days as a medium duration per-man-labour year for the same group.Three groups of VDT operators were examined in terms of trapezius load and pain intensity and duration before and after an ergonomic intervention. All groups reported significant less intensity or duration of pain either in the neck or in the shoulder regions after the intervention. The trapezius load was reduced for all groups post vs. prior intervention. This reduction was measured in terms of a decrease in the static level of APDF and an increase in the number of periods per minute and total duration of muscle activity below 1% MVC. The results from this study indicate that the trapezius load may be a predictor for development of musculoskeletal illness in the neck and shoulder regions.
The aim of this study was to determine how head and neck postures vary when using two media tablet (slate) computers in four common user configurations.
Fifteen experienced media tablet users completed a set of simulated tasks with two media tablets in four typical user configurations. The four configurations were: on the lap and held with the user's hands, on the lap and in a case, on a table and in a case, and on a table and in a case set at a high angle for watching movies. An infra-red LED marker based motion analysis system measured head/neck postures.
Head and neck flexion significantly varied across the four configurations and across the two tablets tested. Head and neck flexion angles during tablet use were greater, in general, than angles previously reported for desktop and notebook computing. Postural differences between tablets were driven by case designs, which provided significantly different tilt angles, while postural differences between configurations were driven by gaze and viewing angles.
Head and neck posture during tablet computing can be improved by placing the tablet higher to avoid low gaze angles (i.e. on a table rather than on the lap) and through the use of a case that provides optimal viewing angles.
The aim of this study was to determine if thumb motor performance metrics varied by movement orientation, direction, and device size during single-handed use of a mobile phone device.
With the increased use of mobile phones, understanding how design factors affect and improve performance can provide better design guidelines.
A repeated measures laboratory experiment of 20 right-handed participants measured the thumb tip's 3-D position relative to a phone during reciprocal tapping tasks across four phone designs and four thumb tip movement orientations. Each movement orientation included two movement directions: an "outward" direction consisting in CMC (carpometacarpal) joint flexion or abduction movements and an "inward" direction consisting in CMC joint extension or adduction movements. Calculated metrics of the thumb's motor performance were Fitts' effective width and index of performance.
Index of performance varied significantly across phones, with performance being generally better for the smaller devices. Performance was also significantly higher for adduction-abduction movement orientations compared to flexion-extension, and for "outward" compared to "inward" movement directions.
For single-handed device use, adduction-abduction-type movements on smaller phones lead to better thumb performance.
The results from this study can be used to design new mobile phone devices and keypad interfaces that optimize specific thumb motions to improve the user-interface experience during single-handed use.
The aim of this study was to evaluate thumb postures, thumb movements and muscle activity when using mobile phones for SMS messaging and to determine whether there were differences in these exposures (a) across various mobile phone tasks, (b) between gender and (c) between subjects with and without musculoskeletal symptoms in shoulders and upper extremities. Fifty-six young adults (15 healthy and 41 with musculoskeletal symptoms) performed a series of distinct tasks on a mobile phone. Muscular load in four forearm/hand muscles in the right arm and the right and left trapezius muscles were measured using electromyography (EMG). Thumb movements were registered using an electrogoniometer. The results showed that postures (sitting or standing) and the type of mobile phone task (holding the phone versus texting) affected muscle activity and thumb positions. Females compared to males had higher muscle activity in the extensor digitorum and the abductor pollicis longus when entering SMS messages and tended to have greater thumb abduction, higher thumb movement velocities and fewer pauses in the thumb movements. Subjects with symptoms had lower muscle activity levels in the abductor pollicis longus and tended to have higher thumb movement velocities and fewer pauses in the thumb movements compared to those without symptoms.
Increased carpal-tunnel pressure has been implicated in the pathophysiology of carpal tunnel syndrome, but it is not known whether splints that immobilize the wrist in a functional position of extension minimize carpal tunnel pressure. To determine the position of the wrist that results in the lowest carpal-tunnel pressure, twenty control subjects and four patients who had carpal tunnel syndrome were evaluated with use of a new, dynamic method that continuously measures carpal tunnel pressure throughout the range of motion of the wrist. The pressure was measured by means of a pressure transducer connected to a flexible catheter that had been inserted into the carpal canal. The position of the wrist was measured simultaneously with use of a two-axis electrogoniometer. Aided by a computer monitor that displayed a moving line of real-time carpal-tunnel pressure, each subject was instructed to move the wrist throughout the range of motion and to adjust it to the position that corresponded to the lowest carpal-tunnel pressure. For the control subjects, the lowest carpal-tunnel pressure averaged 8 +/- 4 millimeters of mercury (1.07 +/- 0.53 kilopascals), and the average position of the wrist associated with the lowest pressure was 2 +/- 9 degrees of extension and 2 +/- 6 degrees of ulnar deviation.(ABSTRACT TRUNCATED AT 250 WORDS)
Small pocket computers offer great potential in workplaces where mobility is needed to collect data or access reference information while carrying out tasks such as maintenance or customer support. This paper reports on three studies examining the hypothesis that data entry by older workers is easier when the pocket computer has a physical keyboard, albeit a small one, rather than a touch-screen keyboard. Using a counter-balanced, within-subjects design the accuracy and speed with which adults over 55 years of age could make or modify short text entries was measured for both kinds of pocket computer. The keyboard computer was the Hewlett Packard 360LX (HP), but the touch-screen computers varied across studies (experiment 1: Apple Newton and PalmPilot; experiment 2: Philips Nino; experiment 3: Casio E10). All studies showed significant decrements in accuracy and speed when entering text via the touch-screen. Across studies, most participants preferred using the HP's small physical keyboard. Even after additional practice with the touch screen (experiments 2 and 3) many entries still contained errors. Experiment 3 showed that younger people were faster but not more accurate than older people at using the touch-screen keyboard. It is concluded that satisfactory text entry on palm-size computers awaits improvements to the touch-screen keyboard or alternative input methods such as handwriting or voice. Interface developments that assist older people typically benefit younger users too.
Our objectives were to estimate prevalence of musculoskeletal disorders among office workers at a newspaper in Mexico City, analyze the relationship between musculoskeletal disorders and use of the personal computer (PC) and associated ergonomic factors in the aforementioned population, and to analyze the modifying effect that psychosocial factors have on the relationship between ergonomic factors and musculoskeletal disorders and extant jobs at the newspaper.
A total of 73% (218 of 298) of office workers at a newspaper were studied. Information was collected by a questionnaire completed by participants. Cases for work-related musculoskeletal disorder in hands (WMSD-H), upper extremity (WMSD-UE), and back (WMSD-B) were established. Working conditions, computer use, and ergonomic and psychosocial factors were studied as independent variables. To study the relationship between musculoskeletal disorders and independent variables, prevalence ratios adjusted for potential confounders (sex, age, educational level, and marital status) were estimated.
Risk of musculoskeletal disorders was greater among workers at the newspaper who used computers, those involved in editing work, and those who adopted uncomfortable positions. The modifying effect of psychosocial factors was observed only in the relationship between ergonomic factors and WMSD-B because among workers with control over work, WMSD-B risk was reduced by the greater number of work breaks. Among workers without social support, increase in number of postures and rotation/inclination of the neck was associated with substantial risk increase, while amid workers under psychological demand number of PC tasks and number of rest pauses were associated with increase in WMSD-B risk.
The findings of our study showed that PC use increased risk of developing musculoskeletal disorders (WMSD-H and WMSD-UE). Such an increase is mediated by ergonomic factors such as mouse use, remaining seated for prolonged periods, adoption of inadequate or uncomfortable postures, performing certain PC tasks, and psychosocial factors.
This review summarizes the knowledge regarding ergonomics and musculoskeletal disorders and the association with computer work. A model of musculoskeletal disorders and computer work is proposed and the evidence and implications of the model together with issues for future research is discussed. The model emphasizes the associations between work organization, psychosocial factors and mental stress on the one hand and physical demands and physical load on the other. It is hypothesized that perceived muscular tension is an early sign of musculoskeletal disorder, which arises as a result of work organizational and psychosocial factors as well as from physical load and individual factors. It is further hypothesized that perceptions of exertion and comfort are other possible early signs of musculoskeletal disorders in computer work. Interventions aimed at reducing musculoskeletal disorders due to computer work should be directed at both physical/ergonomic factors and work organizational and psychosocial factors. Interventions should be carried out with management support and active involvement of the individual workers.
To develop work guidelines for wrist posture based on carpal tunnel pressure. Background: Wrist posture is considered a risk factor for distal upper extremity musculoskeletal disorders, and sustained wrist deviation from neutral at work may be associated with carpal tunnel syndrome. However, the physiologic basis for wrist posture guidelines at work is limited.
The relationship of wrist posture to carpal tunnel pressure was examined in 37 healthy participants. The participants slowly moved their wrists in extension-flexion and radioulnar deviation while wrist posture and carpal tunnel pressure were recorded. The wrist postures associated with pressures of 25 and 30 mmHg were identified for each motion and used to determine the 25th percentile wrist angles (the angles that protect 75% of the study population from reaching a pressure of 25 or 30 mmHg).
Using 30 mmHg, the 25th percentile angles were 32.7 degrees (95% confidence interval [CI] = 27.2-38.1 degrees) for wrist extension, 48.6 degrees (37.7 -59.4 degrees) for flexion, 21.8 degrees (14.7-29.0 degrees) for radial deviation, and 14.5 degrees (9.6-19.4 degrees) for ulnar deviation. For 25 mmHg, the 25th percentile angles were 26.6 degrees and 37.7 degrees for extension and flexion, with radial and ulnar deviation being 17.8 degrees and 12.1 degrees, respectively.
Further research can incorporate the independent contributions of pinch force and finger posture into this model.
The method presented can provide wrist posture guidelines for the design of tools and hand-intensive tasks.
The aim of this study was to analyze the posture of the upper extremities during the use of mobile communication devices. Using various sizes of mobile devices and display characters, we examined subjective muscular loads, viewing distances, and joint angles in the head, neck, shoulder, elbow, and lower back. No postural differences were found between the use of 7-in and 10-in devices, whereas the head and neck were significantly flexed and the elbow angles were decreased during the use of the 13-in device. Character size significantly affected the viewing distance; however, no differences in body angles were found. Participants continually increased their muscular loads during the task by flexing the head and neck, despite their high subjective discomfort levels in the neck and upper arm.
Repetitive or prolonged head flexion posture while using a smartphone is known as one of risk factors for pain symptoms in the neck. To quantitatively assess the amount and range of head flexion of smartphone users, head forward flexion angle was measured from 18 participants when they were conducing three common smartphone tasks (text messaging, web browsing, video watching) while sitting and standing in a laboratory setting. It was found that participants maintained head flexion of 33-45° (50th percentile angle) from vertical when using the smartphone. The head flexion angle was significantly larger (p < 0.05) for text messaging than for the other tasks, and significantly larger while sitting than while standing. Study results suggest that text messaging, which is one of the most frequently used app categories of smartphone, could be a main contributing factor to the occurrence of neck pain of heavy smartphone users. Practitioner Summary: In this laboratory study, the severity of head flexion of smartphone users was quantitatively evaluated when conducting text messaging, web browsing and video watching while sitting and standing. Study results indicate that text messaging while sitting caused the largest head flexion than that of other task conditions.
The use of forearm and palm supports has been associated with lower neck and shoulder muscle activity as well as reduced musculoskeletal discomfort during keyboard use, however, few studies have investigated their effect during computer mouse use. Eight men and eight women completed several computer mousing tasks in six arm support conditions: Forearm Support, Flat Palm Support, Raised Palm Support, Forearm + Flat Palm Support, Forearm + Raised Palm Support, and No Support. Concurrently, an infrared three-dimensional motion analysis system measured postures, six-degree-of-freedom force-torque sensors measured applied forces & torques, and surface electromyography measured muscle activity. The use of forearm support compared to the no support condition was significantly associated with less shoulder muscle activity & torque, and the raised palm support was associated with less wrist extension. Forearm supports reduced shoulder flexion torque by 90% compared to no support. The use of either support also resulted in lower applied forces to the mouse pad. Participants reported less musculoskeletal discomfort when using a support. These results provide recommendations for office workstation setup and inform ergonomists of effective ways to reduce musculoskeletal exposures.
The Rapid Upper Limb Assessment (RULA) is an observation-based screening tool that has been used to assess postural risks of children in school settings. Studies using eye-tracking technology suggest that visual search strategies are influenced by experience in the task performed. This study investigated if experience in postural risk assessments contributed to differences in outcome scores on the RULA and the visual search strategies utilized. While wearing an eye-tracker, 16 student occupational therapists and 16 experienced occupational therapists used the RULA to assess 11 video scenarios of a child using different mobile information and communication technologies (ICT) in the home environment. No significant differences in RULA outcome scores, and no conclusive differences in visual search strategies between groups were found. RULA can be used as a screening tool for postural risks following a short training session regardless of the assessor's experience in postural risk assessments.
Unlabelled:
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.
The objectives of this study were to (a) evaluate electromyography (EMG) repeatability during maximal voluntary isometric knee extension (MKE) and (b) develop a protocol yielding the most reproducible EMG. Subjects, 11 volunteers, performed 3 MKE (1.05 rad flexion) twice, separated by at least 5 days. EMG was recorded from vastus lateralis, vastus medialis, and rectus femoris. Root-mean-square (RMS) and integrated rectified (IEMG) values were determined across 4 averaging windows (W = 100, 200, 500, 1000 ms). Coefficients of variation (CV) and intraclass correlations (ICC) described variability and reproducibility among trials and days. Error between days was assessed by the technical error of measurement (TEM) statistic. MKE was highly reproducible (ICC = 0.93). For EMG, trial-to-trial variability was lower than day-to-day for all W, and wider W (i.e., 500 or 1000 ms) minimized variability. TEM was consistently greatest for W=100 ms, indicating that more error was introduced at narrow W. No differences in repeatability were found between RMS-EMG and IEMG. To summarize, EMG variability is minimized within days by increasing W. Day-to-day variability exceeds trial-to-trial and should be considered when reporting treatment effects.
(C) 1997 National Strength and Conditioning Association
Design features of mobile computing technology such as device size and key location may affect thumb motor performance during single-handed use. Since single-handed use requires the thumb posture to vary with key location, we hypothesize that motor performance is associated with thumb and wrist joint postures. A repeated measures laboratory experiment of 10 right-handed participants measured thumb and wrist joint postures during reciprocal tapping tasks between two keys for different key pairs among 12 emulated keys. Fitts' effective index of performance and joint postures at contact with each key were averaged across trials for each key. Thumb motor performance varied for different keys, with poorest performances being associated with excessive thumb flexion such as when tapping on keys closest to the base of the thumb in the bottom right corner of the phone. Motor performance was greatest when the thumb was in a typical resting posture, neither significantly flexed nor fully extended with slight CMC joint abduction and supination, such as when tapping on keys located in the top right and middle left areas on the phone. Grip was also significantly affected by key location, with the most extreme differences being between the top left and bottom right corners of the phone. These results suggest that keypad designs aimed at promoting performance for single-handed use should avoid placing frequently used functions and keys close to the base of the thumb and instead should consider key locations that require a thumb posture away from its limits in flexion/extension, as these postures promote motor performance.
Background and Purpose
The Biometrics Flexible electrogoniometer has the potential to allow physiotherapists to record the motion of joints during dynamic functional activities. In order to make full and appropriate use of this device it is necessary to comprehend the design, attachment and measurement properties of this instrument.
Methods
The measurement properties of the Biometrics flexible electrogoniometer were investigated using a series of controlled experiments. The in vivo performance of the device was evaluated by comparing the results of the electrogoniometer to those from a TV motion analysis system while measuring knee movement during gait in five normal subjects.
Results
The results of these studies indicate that the electrogoniometers are stable, precise, accurate and repeatable in performance. Little variation exists between electrogoniometers or between the performance of an electrogoniometer at different times, on different days or in different environmental conditions. Small hysteretic effects and inaccuracies are present in the devices but these are of the order of 1 or 2 degrees. The system is not affected by environmental pollutants such as heat, electrical interference, convection currents or noise and therefore can be used in a variety of hospital settings. The device is however affected by abduction/adduction angle with angles of 40° or more giving substantial errors when associated with simultaneous flexion or extension.
Conclusions
The electrogoniometer should be attached firmly and securely across the joint in an essentially planar configuration. Provided care is taken to handle and mount the electrogoniometers appropriately they appear to record knee movement faithfully and accurately and the system is capable of giving valid and meaningful clinical data.
This research study analysed the interaction between people's postures and activities while in semi-public/leisure situations and during transportation (journey by train). In addition, the use of small electronic devices received particular emphasis. Video recordings in German trains and photographs in Dutch semi-public spaces were analysed using a variation of Branton and Grayson's (An evaluation of train seats by observation of sitting behaviour. Ergonomics, 10 (1), (1967), 35-51) postural targeting forms and photos. The analysis suggests a significant relationship between most activities and the position of the head, trunk and arms during transportation situations. The relationship during public situations is less straightforward. Watching, talking/discussing and reading were the most observed activities for the transportation and leisure situations combined. Surprisingly, differences in head, trunk, arm and leg postures were not significant when using small electronic devices. Important issues not considered in this study include the duration of the activities, the gender and age of observed subjects and the influence of the time of day. These are interesting issues to consider and include for future research. STATEMENT OF RELEVANCE: This study shows what activities people choose to carry out and their related postures when not forced to a specific task (e.g. driving). The results of this study can be used for designing comfortable seating in the transportation industry (car passenger, train, bus and aircraft seats) and semi-public/leisure spaces.
An experimental study was conducted to evaluate physical risk factors associated with the use of touchscreen in a desktop personal computer (PC) setting. Subjective rating of visual/body discomfort, shoulder and neck muscle activity, elbow movement and user-preferred positions of the workstation were quantified from 24 participants during a standardised computer use task with a standard keyboard and a mouse (traditional setting), with a touchscreen and the standard keyboard (mixed-use condition) and with the touchscreen only. The use of a touchscreen was associated with a significant increase of subjective discomfort on the shoulder, neck and fingers, myoelectric activity of shoulder and neck muscles and percentage of task duration that arms were in the air. Participants placed the touchscreen closer and lower when using touch interfaces compared with the traditional setting. Results suggest that users would need more frequent breaks and proper armrests to reduce physical risks associated with the use of a touchscreen in desktop PC settings. Statement of Relevance: In this study, subjective discomfort, work posture and muscle activity of touchscreen desktop PC users were quantitatively evaluated. The findings of this study can be used to understand potential risks from the use of a touchscreen desktop PC and to suggest design recommendations for computer workstations with the touchscreen.
Mobile device text messaging and other typing is rapidly increasing worldwide. A checklist was utilized to characterize joint postures and typing styles in individuals appearing to be of college age (n = 859) while typing on their mobile devices in public. Gender differences were also ascertained. Almost universally, observed subjects had a flexed neck (91.0%, n = 782), and a non-neutral typing-side wrist (90.3%, n = 776). A greater proportion of males had protracted shoulders (p < 0.01, χ(2) test), while a greater proportion of females had a typing-side inner elbow angle of <90°, particularly while standing (p = 0.03, χ(2) test). 46.1% of subjects typed with both thumbs (two hands holding the mobile device). Just over one-third typed with their right thumb (right hand holding the mobile device). No difference in typing styles between genders was found. Future research should determine whether the non-neutral postures identified may be associated with musculoskeletal disorders.
The study aims were, in a population of university students, staff, and faculty (n = 140), to: 1) determine the distribution of seven measures of mobile device use; 2) determine the distribution of musculoskeletal symptoms of the upper extremity, upper back and neck; and 3) assess the relationship between device use and symptoms. 137 of 140 participants (98%) reported using a mobile device. Most participants (84%) reported pain in at least one body part. Right hand pain was most common at the base of the thumb. Significant associations found included time spent internet browsing and pain in the base of the right thumb (odds ratio 2.21, 95% confidence interval 1.02-4.78), and total time spent using a mobile device and pain in the right shoulder (2.55, 1.25-5.21) and neck (2.72, 1.24-5.96). Although this research is preliminary, the observed associations, together with the rising use of these devices, raise concern for heavy users.
We compared personal histories of 57 cases and 122 age-matched controls to identify possible environmental determinants of Parkinson's disease (PD). Odds ratios (OR) adjusted for sex, age, and smoking were computed using stepwise logistic regression. We found a statistically significant increased risk for working in orchards (OR = 3.69, p = 0.012, 95% CI = 1.34, 10.27) and a marginally significant increased risk associated with working in planer mills (OR = 4.11, p = 0.065, 95% CI = 0.91, 18.50). A Fisher's exact test of the association between PD development and (1) paraquat contact, and (2) postural tremor gave statistically significant probability estimates of 0.01 and 0.03, respectively. The relative risk of PD decreased with smoking, an inverse relationship supported by many studies.
In order to analyse the effect of changing the sitting posture on the level of neck and shoulder muscular activity, an electromyographic (EMG) study of ten healthy experienced female workers from an electronics plant was undertaken. A standardized, simulated task was performed in eight different sitting work postures. Using surface electrodes, the level of muscular activity was recorded as normalized, full-wave rectified low-pass filtered EMG. The results showed that the whole spine flexed sitting posture gave higher levels of static activity in several neck and shoulder muscles than the posture with a straight and vertical spine, which in turn gave higher levels than the posture with slightly backward-inclined thoraco-lumbar spine.
The exposure to local muscular strain during work may be evaluated by vocational electromyography. The aim of the presentation is to briefly describe how electromyography may be used to analyse the muscular strain during work. Different methods for quantifying the myoelectric results are discussed. A brief description of the use of amplitude probability distribution analysis of the myoelectric signals obtained during work is given. A few examples of results obtained from the upper portion of the right and left trapezius muscle in different work situations are presented.
This study concerned the influence of 6 positions of the computer mouse on the work table on posture, muscular load, and perceived exertion during text editing.
An optoelectronic 3-dimensional motion analysis system was used to register the postures of 10 men and 10 women using video display units. Muscular load was also registered (with electromyography), as was perceived exertion (with rating scales).
A neutral posture with a relaxed and supported arm showed the least perceived exertion, and the electromyographic results showed low activity in both trapezius muscles in this position. Short operators (all women) showed a numerically higher activity in the 4 examined muscles than the tall operators (all men, except 1). This finding could be related to lower muscle force among women and to anthropometric differences, which also influence biomechanic load moments. Narrow-shouldered operators (8 women and 1 man) and short operators worked with larger outward rotation and abduction of the shoulder in a position of the mouse lateral to the keyboard than the broad-shouldered (7 men and 2 women) and tall operators did. Arm support markedly reduced muscle load in the neck-shoulder region among the operators.
The operators using video display units in this study preferred to use the mouse on a table in a close to relaxed, neutral posture of the arm in combination with arm support. Short and narrow-shouldered operators worked in more strenuous postures of the arm when the mouse was located lateral to the keyboard.
The purpose was to assess risk factors in dentistry which may contribute to musculoskeletal disorders. A questionnaire was used to identify common work tasks, and to estimate one year prevalence for troubles (65% for the neck/shoulder, 59% for the low back). In a field study working postures and electromyography (shoulder/neck) were registered during the three most common work tasks. Prolonged neck flexion and upper arm abduction were found, as well as high static muscle activity levels (splenius and trapezius muscles). No differences between work tasks were found regarding postures, frequencies of movements or muscle activity. Alterations between the three work tasks do not produce sufficient variation to reduce musculoskeletal load on the neck and shoulders.
The nature of work-related musculoskeletal disorders of the neck and upper limbs is reviewed using both scientific data and the consensus view of experts, union bodies and government agencies across the European Union. Work-related musculoskeletal disorders describe a wide range of inflammatory and degenerative diseases and disorders. These conditions result in pain and functional impairment and may affect, besides others, the neck, shoulders, elbows, forearms, wrists and hands. They are work-related when the work activities and work conditions significantly contribute to their development or exacerbation but are not necessarily the sole determinant of causation. The classification and the need for standardised diagnostic methods for assessment of neck and upper limb musculoskeletal disorders are reviewed. These disorders are a significant problem within the European Union with respect to ill health, productivity and associated costs. The pathomechanisms of musculoskeletal disorders affecting tendons, ligaments, nerves, muscle, circulation and pain perception are reviewed and conceptual models for the pathogenesis of musculoskeletal disorders affecting the neck and upper limbs are presented. The epidemiological evidence on the work-relatedness of these disorders is discussed. A relationship between the performance of work and the occurrence of neck and upper limb musculoskeletal disorders is evident. Intervention strategies in the workplace for the reduction of both exposure and effect should focus upon factors within the work organisation as well as actively involving the individual worker. The current knowledge is sufficient to enable informed decisions to be made on future research needs and prevention strategies at the societal, organisational and individual level.
With the increasing use of video display terminals (VDTs), there is growing concern over the corresponding increase in the number of health problems reported. Although much research has focused on identifying the optimal screen height, there is to date no consensus. This study aimed to investigate the effect of prolonged (89 min) VDT work at four different screen heights on head-neck posture, muscle activity and the development of muscle fatigue. The results show that lowering screen height, starting from 15 cm above the baseline (i.e. top of the screen level with eye height while sitting), decreased the ear-eye angle, increased the viewing angle, increased the viewing angle relative to the ear-eye line, and increased the muscle activity of the neck extensor muscles. There were also some significant time effects on postural angles and muscle activity. In this study there were only rare occurrences of muscle fatigue, defined as a simultaneous increase in EMG amplitude and a shift of the EMG power spectrum to lower frequencies. Muscle activity increased significantly in some muscles and for certain screen heights.
A Case with isolated pain and swelling at the base of the left thumb is reported. The problem had lasted for 2 years, and it was getting worse with increasing pain also at the base of the right thumb. The X-ray showed a subluxation and an arthritis of the first CMCJ was diagnosed in left hand. An excision arthroplasty was successfully carried out. The excessive mobile phone use with active texting had been probably the main cause of the problem. Many, especially youngsters use their phones to text and play games a lot. The purpose of this report is to make the researchers and practitioners aware of this problem and to encourage them to record these cases that may be common in future.
A Prospective Study of Computer Users: II. Postural Risk Factors for Musculoskeletal Symptoms and Disorders
- M Marcus
- F Gerr
- C Monteilh
- D J Ortiz
- E Gentry
- S Cohen
- A Edwards
- C Ensor
- D Kleinbaum
Mobile Marketing Association, and Interactive Advertising Bureau
- Ipsos Mediact