The influence of a semi-reclined seated posture on head and neck kinematics and muscle activity while reading a tablet computer

Comparison of Cervical Spine Kinematics and Clinical Neck Symptoms Between Mobile Device and Desktop Computer Use

The widespread use of mobile devices and desktop computers has been associated with mechanical neck symptoms, yet few studies have compared cervical kinematics and clinical symptoms between them. In this study, 15 participants (27.7 ± 4.4 years, 12 male) performed four randomly ordered 20 min tasks: two mobile (smartphone and tablet) and two desktop computer (keyboard and mouse) tasks. Kinematic variables, including neck flexion, lateral bending, axial rotation, anterior translation, and total distance moved, were measured using an optical motion capture system, while clinical symptoms, including discomfort, pain, tension, and fatigue, were assessed using a visual analog scale. Paired t-tests and linear mixed models were used for analysis. Results showed that mobile device users exhibited greater neck flexion (38.9° [32.1-45.6°] vs. -0.2° [-4.3-3.9°], p < 0.001) and anterior translation (21.0 cm [12.0-30.1] vs. 1.6 cm [-4.4-7.7], p < 0.001) compared to desktop users. All clinical symptoms were significantly higher during mobile device use (p < 0.05), with neck flexion and anterior translation strongly correlating with symptom severity. In conclusion, mobile device use leads to more severe neck symptoms compared to desktop computer use, which is associated with increased flexion and forward head posture. To reduce neck symptoms, avoiding sustained flexion and forward head positions during mobile device use is recommended.

The influence of chair recline and head and neck position on upper trapezius activity and stiffness during seated computer work

Increasing chair recline during seated computer work may reduce the load placed on the upper trapezius (UT), a common location of pain for those with idiopathic chronic neck pain. This study determined the effect of increasing chair recline on UT stiffness and muscle activity during computer work in people with and without idiopathic chronic neck pain. Surface electromyography and ultrasound shear wave elastography were collected from three subdivisions of the UT in 15 individuals with idiopathic chronic neck pain and 15 sex-matched healthy controls. Participants sat in a standardized computer-work setup while chair recline (0°, 25°, 45°) and head and neck position (self-selected, neutral, flexed) were systematically adjusted and maintained for 2.5-min intervals. Repeated-measures ANOVAs were completed for each sex, muscle, and data type, with group (chronic neck pain, control), chair recline (0°,25°,45°), head and neck position (self-selected, flexed, neutral), and side of collected data (dominant, non-dominant) as fixed factors. Men with idiopathic chronic neck pain demonstrated greater UT stiffness in the cranial subdivision when compared to healthy men. Additionally, the 25° and 45° recline levels increased the stiffness of men's dominant UT compared to men's non-dominant UT. Women's UT was more affected by head and neck position, and a neutral head and neck position resulted in lower UT activation, but higher UT stiffness for the cranial subdivision and midway between C-7 and the acromion process. Overall, our findings suggest that the commonly suggested neutral position may not be a beneficial prompt when positioning someone during seated computer work.

Alterations in Cervical Nerve Root Function during Different Sitting Positions in Adults with and without Forward Head Posture: A Cross-Sectional Study

The current study aimed to determine whether participants with and without forward head posture (FHP) would respond differently in cervical nerve root function to various sitting positions. We measured peak-to-peak dermatomal somatosensory-evoked potentials (DSSEPs) in 30 participants with FHP and in 30 participants matched for age, sex, and body mass index (BMI) with normal head posture (NHP), defined as having a craniovertebral angle (CVA) >55°. Additional inclusion criteria for recruitment were individuals between the ages of 18 and 28 who were in good health and had no musculoskeletal pain. All 60 participants underwent C6, C7, and C8 DSSEPs evaluation. The measurements were taken in three positions: erect sitting, slouched sitting, and supine. We identified statistically significant differences in the cervical nerve root function in all postures between the NHP and FHP groups (p < 0.001), indicating that the FHP and NHP reacted differently in different positions. No significant differences between groups for the DSSEPs were identified for the supine position (p > 0.05), in contrast to the erect and slouched sitting positions, which showed a significant difference in nerve root function between the NHP and FHP (p < 0.001). The NHP group results were consistent with the prior literature and had the greatest DSSEP peaks when in the upright position. However, the participants in the FHP group demonstrated the largest peak-to-peak amplitude of DSSEPs while in the slouched position as opposed to an erect position. The optimal sitting posture for cervical nerve root function may be dependent upon the underlying CVA of a person, however, further research is needed to corroborate these findings.

Effects of typing positions on the upper trapezius and neck extensor muscles electromyography in office employees: A single-blind cross-sectional study

BACKGROUND

Holding incorrect postures over a long period could lead to chronic nonspecific neck pain (CNNP) in office employees.

OBJECTIVE

The present study aimed to evaluate the effects of different typing positions on the activity of the neck extensor and upper trapezius (UT) muscles of office employees diagnosed with CNNP.

METHODS

This assessor-blinded cross-sectional study was performed on 22 female subjects with the mean age of 39.95±5.30 years. The neck extensors and UT muscle activities of the participants were assessed in the upright, forward, and slouching postures by electromyography (EMG). In addition, neck proprioception and the performance of the cervical stabilizer muscles were evaluated using an inclinometer and biofeedback pressure unit, respectively.

RESULTS

A significant difference was observed between the cervical erector spine (CES) and UT muscle activities in the upright, forward, and slouching typing positions (P < 0.05). In addition, a difference was observed between the upright and slouching postures in these muscles. A positive correlation was denoted between CES muscle activity in the slouching and forward postures and the activation index of neck muscles (P < 0.05). Furthermore, a significant, negative correlation was observed between the UT muscle activity in the slouching posture and neck proprioception (P < 0.05). A positive correlation was also noted between the pain index and repositioning error rates (P < 0.05).

CONCLUSION

CES muscle activity increased in a forward head posture, which could damage neck proprioception through causing early fatigue and stimulating a cumulative damage cycle.

Effects of lying posture and task type on muscle fatigue, visual fatigue, and discomfort while using a smartphone on the bed

BACKGROUND

Neck-shoulder and arm musculoskeletal disorders in smartphone use have attracted increasing attention.

OBJECTIVE

This study aimed to examine the effect of different lying postures and task types by comparing the electrooculography (EOG) responses, perceived discomfort, and the activity of neck-shoulder and arm muscles while using a smartphone on the bed.

METHODS

Twenty participants were recruited to perform 30-min tasks (texting/ watching video) while holding the smartphone in three different lying postures (half-lying/lying/side-lying). Subjective discomfort, muscular activities including the abductor pollicis brevis (APB), upper trapezius (UT), and extensor carpi radialis (ECR), and EOG signals were simultaneously monitored.

RESULTS

The results showed that the perceived discomfort of measured body parts increased significantly over time in all postures. Watching video significantly increases muscle activities of APB and UT and decreases blink frequency and blink duration. Compared to lying or half-lying, the side-lying posture has the highest blink frequency, blink duration, and muscle activities in ECR and UT.

CONCLUSION

The findings of this study indicate that side-lying posture should be avoided while using a smartphone on the bed. It provides an understanding of the association between the postures of using smartphones on the bed and fatigue, which can help prevent muscle and visual fatigue in smartphone use.

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

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

Differences in upper body posture between individuals with and without chronic idiopathic neck pain during computerised device use: A 3D motion analysis study

BACKGROUND

Computer use is associated with poor postures and increased risk of developing neck pain. Evaluating differences in working posture of individuals with and without chronic neck pain may assist the development of strategies to lessen or prevent pain.

OBJECTIVE

To identify if upper body kinematics differs between individuals with and without chronic idiopathic neck pain during four conditions (tablet, laptop, and desktop computer sitting and standing).

METHODS

Three-dimensional (3D) motion capture measured upper body kinematics in 44 individuals with chronic idiopathic neck pain > 90 days (Cases n = 22) and without pain (Control n = 22), during a typing task under four conditions: tablet, laptop, desktop computer (sitting and standing). Differences between groups were evaluated using generalised linear mixed models.

RESULTS

Across all conditions and compared to controls, cases had significantly less flexion between their head-neck and upper trunk segments (between group mean difference 7.15°, 2.1, 12.2, p = .006), greater upper trunk flexion relative to the laboratory (-6.15°, -10.9, -1.3, p = .012), greater shoulder flexion bilaterally (left 12.35°, 6.7, 17.9, p < .001; right 13.49°, 7.9, 19.1, p < .001) and less right elbow flexion (-6.87°, -12.1, -1.7, p = .010). Approaching significance, the case group had less left elbow flexion (between group mean difference -5.36°, -10.9, 0.1, p = .056) and a smaller mean craniocervical angle for the seated desktop condition (group x condition interaction -6.37°; 95% CI -12.7, -0.1, p = .052).

SIGNIFICANCE

Individuals with neck pain consistently used different upper body postures compared to individuals without pain when working on computerised devices under varying workstation conditions. This finding suggests that people with neck pain work in potentially aggravating postures that may be associated with their pain.

Spine Posture, Mobility, and Stability of Top Mobile Esports Athletes: A Case Series

Professional esports athletes spend a long time in the same sitting posture during training and competition. Mobile esports may exacerbate potential postural problems because of the closer and unsupported arms and because athletes spend more time in a forward-/flexed-head posture. Prolonged sitting in these postures carries significant health risks and may lead to musculoskeletal problems and injuries. The objective of this retrospective study is to assess the posture, mobility, and stability of the spine for professional mobile esports athletes. We collected spine-assessment data from 48 athletes participating in a top-tier league on a real-time-strategy battle-arena online game. The spinal assessment was conducted using the SpinalMouse® under upright standing and trunk flexion in addition to the Matthiass test. Measurements were converted into Idiag Scores by the SpinalMouse® software. The Idiag Posture, Idiag Mobility, and Idiag Stability scores were 62.50 (IQR: 21), 63.50 (IQR: 19.5), and 54.50 (IQR: 14.5), respectively, and were significantly lower (p < 0.001) than the reference normative value (100). Age was found to have a weak positive correlation with the posture score (ρ = 0.29, p = 0.048). Although career duration appeared to lower the scores, the association was insignificant (p > 0.05). The scores also had no significant association with body height, body mass, body mass index, and esports team (p > 0.05). It was anticipated that mobile-based esports would attenuate the biomechanics of the spine and increase the likelihood of musculoskeletal problems, such as neck and back pain.

Evaluating the impact of writing surface and configuration on muscle activation level during a handwriting task: An exploratory study

BACKGROUND: Tablets are ubiquitous in workplaces and schools. However, there have been limited studies investigating the effect tablets have on the body during digital writing activities. OBJECTIVE: This study investigated the biomechanical impact of writing interface design (paper, whiteboard, and tablet) and orientation (horizontal, 45°, and vertical) on tablet users. METHODS: Fourteen adults (7 male, 7 female) participated in a study during which they performed simple writing tasks. Surface electromyography (sEMG) sensors were used to measure upper extremity muscle activation. RESULTS: Results indicate that the effects of writing surface type were most pronounced in forearm muscle activation. Specifically, in the extensor carpi radialis (ECR), where muscle activity was lower on the tablet PC surface. The effects of writing configuration were prominent in the shoulder and forearm. The activation of the flexor carpi ulnaris (FCU) and trapezius muscles was significantly lower in the 45° configuration. An exception to the efficacy of this configuration was the anterior deltoid muscle, which exhibited the lowest muscle activity in the horizontal orientation. CONCLUSIONS: Tablet surface and the 45° configuration resulted in the lowest muscle activation levels. Future studies should include longer experiment duration to investigate the effects of continuous writing.

Using touchscreen mobile devices-when, where and how: a one-week field study

This cross-sectional study explored the objectively measured Touchscreen Mobile Device (TSMD) use in free-living conditions. Data on TSMD use, gross body posture (lying, sitting, standing, stepping), and location of use (workplace, home, other) were collected over seven consecutive days from 54 adults (mean ± SD, 38 ± 10 years). The average duration of TSMD use was 152 ± 91 min/day, with a TSMD engagement of 51 ± 35 times/day. Participants under 30 years spent significantly more time on their TSMD, averaging 230 ± 108 min/day. By location, 54 ± 17% of use occurred at home and 24 ± 15% at work. The most common posture adopted during any TSMD use was sitting (77 ± 5 2 min/day), with participants also spending considerable time lying down in the home environment (39 ± 49 min/day). These findings provide valuable insights into how adults are using TSMDs, including the postures and locations of use. Further research is needed on the health and wellbeing implications of these usage patterns. Practitioner summary: This study explored Touchscreen Mobile Device (TSMD) use in free-living conditions among 54 adults (mean ± standard deviation, 38 ± 10 years). Participants under 30 years spent significantly more time on their devices. More than half of the time spent using TSMD occurred at home while sitting and lying down.Abbreviations: TSMD: touchscreen mobile device; SD: standard deviation; MSD: musculoskeletal disorder; HDR: higher degree by research; SEES: School of Earth and Environmental Sciences; UK: The United Kingdom; USA: United States of America; SAS: statistical analysis system; ANOVA: analysis of variance; SPSS: statistical package for the social sciences; h: hour; min/d: minutes per day; d: day; ICC: intraclass correlation; CI: confidence interval; min: minute; GPS: global positioning systemsHighlightsTouchscreen mobile device use and gross body posture were quantified objectively.The most common postures for touchscreen mobile device use were lying and sitting.Touchscreen mobile devices were used around twice as much at home than at work.Use at home, with a predominance of the lying posture, needs further investigation.

Impact of digital boards on hand and neck muscle activity during online teaching process

Academicians across the globe due to Covid 19 shifted to online teaching as a mainstream method by replacing the chalk and talk method. The main objective of this study is to find the impact of different sizes of digital boards used for online teaching on muscle activity and muscle fatigue, and then results are compared with conventional writing. Initially, a questionnaire survey is conducted among 100 college professors about the issue they faced while using online teaching methods. Experimental analysis are then conducted using electromyography sensor (sEMG) among ten college professors and their muscle activity on the dominant hand and neck while writing on two commercially available digital boards namely Type 1 (small writing area) and Type 2 (large writing area). Four muscles namely Flexor carpi radialis, Extensor carpi radialis, Biceps brachii, and Sternocleidomastoid (SCM) are chosen for the study. The results are then compared with muscle activity while writing on conventional A4 sheets. Normalized root mean square (RMS) is used to assess the muscle activity and the trend line of MPF value is utilized to assess the muscle fatigue. The results show that SCM muscle has more muscle activation compared to other selected muscles followed by flexor carpi radialis. Subjective analysis is carried out using the Borg scale, which has reported that Type 2 digital board having larger working area was preferred by the participants as it reduces muscle fatigue.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Acute Pain, Neck Extensor Endurance, and Kinematic Changes Resulting from Sustained Neck Flexion during Smartphone Use

OCCUPATIONAL APPLICATIONSThe 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.

An Electromyographically Driven Cervical Spine Model in OpenSim

Relatively few biomechanical models exist aimed at quantifying the mechanical risk factors associated with neck pain. In addition, there is a need to validate spinal-rhythm techniques for inverse dynamics spine models. Therefore, the present investigation was 3-fold: (1) the development of a cervical spine model in OpenSim, (2) a test of a novel spinal-rhythm technique based on minimizing the potential energy in the passive tissues, and (3) comparison of an electromyographically driven approach to estimating compression and shear to other cervical spine models. The authors developed ligament force-deflection and intervertebral joint moment-angle curves from published data. The 218 Hill-type muscle elements, representing 58 muscles, were included and their passive forces validated against in vivo data. Our novel spinal-rhythm technique, based on minimizing the potential energy in the passive tissues, disproportionately assigned motion to the upper cervical spine that was not physiological. Finally, using kinematics and electromyography collected from 8 healthy male volunteers, the authors calculated the compression at C7-T1 as a function of the head-trunk Euler angles. Differences from other models varied from 25.5 to 368.1 N. These differences in forces may result in differences in model geometry, passive components, number of degrees of freedom, or objective functions.

Neck Muscular Load When Using a Smartphone While Sitting, Standing, and Walking

OBJECTIVE

Myoelectric activity of neck extensor muscles and head kinematic variables, when using a smartphone for one-handed browsing and two-handed texting while sitting, standing, and walking, were evaluated to compare the neck muscular load during these tasks and across the posture conditions.

BACKGROUND

There has been limited research on the relation between head-down postures and the muscular load on the neck of smartphone users.

METHODS

Twenty-one asymptomatic young users were asked to perform one-handed browsing and two-handed texting tasks in each of the posture conditions, and the myoelectric activities of the neck extensor muscles, head kinematic variables, and upper back posture were quantified.

RESULTS

The muscle activation level when using a phone during walking was 21.2% and 41.7% higher than that of sitting and standing on average (p < .01). Head vertical and angular accelerations were also significantly greater (p < .01) for walking than for sitting and standing conditions. Between the two conducted tasks, participants flexed their heads more significantly (p < .01) with higher activation of the neck extensor muscles (p < .01) when texting as compared to when browsing.

CONCLUSION

Results indicate that two-handed texting while walking would be the most physically demanding scenario for neck musculature, and it might be attributable to the dynamics of the head while walking with the head facing downwards.

APPLICATION

These findings can be used to better understand the potential relation between smartphone use and the occurrence of neck musculoskeletal problems and to inform the users of the ergonomic risks of using smartphones while walking.

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

Introduction

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

Method

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

Results

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

Conclusion

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

The effect of the use of smartphone while walking on the electromyography activity of the lower extremity in young students

The study aims to determine the effects of smartphone use on the muscle activity of the lower extremity when walking. Twenty-three healthy young students were asked to perform a 10-m walk test between normal walking without using a smartphone and walking while two-handed texting on a smartphone. The electromyography activities of the lower extremity were quantified. To quantitatively assess the cervical flexion range of smartphone users, the cervical flexion angle was measured using a digital goniometer. The study results indicated that the use of a smartphone while walking could lessen muscle activity on the tibialis anterior, gastrocnemius, rectus femoris, gluteus maximus, and gluteus medius than that of normal walking without using a smartphone. The walking speeds were reduced in walking while using a smartphone compared with normal walking without using a smartphone. The cervical flexion angle was greater when walking while using a smartphone compared to that of normal walking without using a smartphone. These results suggest that frequently using a smartphone while walking could be a potential risk for musculoskeletal problems.

The influence of smartphone use on spinal posture - A laboratory study

BACKGROUND

Smartphones have become increasingly more popular and complicated tasks can be performed with these devices. However, the increasing use is associated with shoulder and neck pain, as well as with psychological addiction.

RESEARCH QUESTION

Do different smartphone tasks lead to changes in spinal posture and pelvic position? Is there a relationship between smartphone addiction and changes in posture?

METHODS

A cross-sectional study including 50 participants was performed. Test subjects completed the Smartphone Addiction Scale and the SF-36 health questionnaire. Subjects spinal posture and pelvic position during different smartphone tasks were measured through a surface topography system. The different tasks were: standing in an upright position, simulating a phone call, texting with one or two hands during standing or while walking on a treadmill. Paired T-tests and ANOVA tests were performed to evaluate differences. The Kendall rank test was used to investigate the association between clinical scores and changes in spinal posture.

RESULTS

All smartphone tasks lead to a significant increase in thoracic kyphosis and trunk inclination during standing and while walking. A significant increased lumbar lordosis was also found. Texting with one or two hands correlated with increased surface rotation. No associations between smartphone addiction and changes of the spinal posture were reported.

SIGNIFICANCE

This represents the first surface topography study that investigated the influence of different smartphone tasks on the spinal posture and pelvic position during standing and while walking. With the results of this study we demonstrated that smartphone use leads to significant changes of sagittal and frontal spine parameters. Further research should focus on the evaluation of possible detrimental effects of long-term smartphone use on the spinal posture and on the development of preventive measures.

Cervical Spine Musculotendon Lengths When Reading a Tablet in Three Seated Positions

A popular posture for using wireless technology is reclined sitting, with the trunk rotated posteriorly to the hips. This position decreases the head's gravitational moment; however, the head angle relative to the trunk is similar to that of upright sitting when using a tablet in the lap. This study compared cervical extensor musculotendon length changes from neutral among 3 common sitting postures and maximum neck flexion while using a tablet. Twenty-one participants had radiographs taken in neutral, full-flexion, and upright, semireclined, and reclined postures with a tablet in their lap. A biomechanical model was used to calculate subject-specific normalized musculotendon lengths for 27 cervical musculotendon segments. The lower cervical spine was more flexed during reclined sitting, but the skull was more flexed during upright sitting. Normalized musculotendon length increased in the reclined compared with an upright sitting position for the C4-C6/7 (deep) and C2-C6/7 (superficial) multifidi, semispinalis cervicis (C2-C7), and splenius capitis (Skull-C7). The suboccipital (R2 = .19-.71) and semispinalis capitis segment length changes were significantly correlated with the Skull-C1 angle (0.24-0.51). A semireclined reading position may be an ideal sitting posture to reduce the head's gravitational moment arm without overstretching the assessed muscles.

Differences in the activity of the shoulder girdle and lower back muscles owing to postural alteration while using a smartphone

The purpose of this study was to clarify the influence of different postures on the activity of the shoulder girdle and lower back muscles while using a smartphone. Sixteen healthy male participants maintained two postures while using a smartphone : a good posture in which the tragus and acromion were closer to the vertical line passing through the greater trochanter, and a poor posture in which the tragus and acromion were farther from the vertical line passing through the greater trochanter. The target muscles were the rhomboid major (Rhom), upper trapezius, middle trapezius, lower trapezius (LT), lumbar erector spinae (LES), and lumbar multifidus (LMF). The activities of the Rhom and LT were significantly lower with poor posture than those with good posture. The activities of LES and LMF were significantly higher with poor posture than those with good posture. The results of this study indicated that poor posture was associated with hypoactivity of the shoulder girdle muscles and hyperactivity of the lower back muscles when compared with good posture. Poor posture for prolonged periods while using a smartphone would lead to malfunction of the shoulder girdle muscles and musculofascial lower back pain. J. Med. Invest. 67 : 274-279, August, 2020.

Posture during the use of electronic devices in people with chronic neck pain: A 3D motion analysis project

BACKGROUND

Non-neutral postures during computerised device use coupled with increased usage may increase the risk of neck pain. Greater knowledge of postures that individuals with neck pain adopt during computerised device use is warranted.

OBJECTIVE

To evaluate neck and upper limb posture while using a tablet, laptop and desktop computer (sitting and standing) in individuals with chronic neck pain.

METHODS

Differences in three-dimensional kinematic variables were assessed during four conditions: tablet, laptop, desktop computer (sitting and standing) in 22 individuals with chronic neck pain >3 months. Differences between kinematic variables were determined using one-way repeated measures ANOVA with Bonferroni post-hoc tests.

RESULTS

Compared to the desktop (sitting), tablet and laptop use resulted in increased neck flexion (mean difference tablet - 14.42°, 95% CI - 19.88, -8.96, P < 0.001; laptop -7.19°, -12.08, -2.31, P = .020); upper trunk flexion (tablet -14.89°, -20.22, -9.56, P < 0.001; laptop -5.56°, -10.02, -1.09, P = .009) and tablet bilateral shoulder elevation (left 11.01 mm, 2.01, 20.04, P < .016; right 13.08 mm, 3.09, 23.11, P < .006).

CONCLUSIONS

Tablet and laptop use resulted in greater neck flexion, bilateral shoulder elevation and upper trunk flexion compared to a standard desktop computer, suggesting individuals with chronic neck pain should be mindful of their posture when using these smaller devices. Future research should explore how differences in posture may influence neck pain.

Sex and Height Influence Neck Posture When Using Electronic Handheld Devices

With increased tablet ownership in the United States comes increased levels of neck flexion compared to desktop or laptop computer use, and these neck postures have been linked to increases in neck pain. Importantly, tablet viewing postures can be achieved in multiple ways and could be determined by the morphology of the individual and/or other extraneous factors. In this study, we aim to preliminarily evaluate how neck postures vary during tablet use among individuals and link this variation to other factors such as sex, height, weight, presence/absence of temporomandibular joint disorder (TMD), and morphology of the head and neck. We analyzed two-dimensional landmarks placed on lateral-view radiographs of 22 participants (10 female and 12 male) seated in neutral, upright, fully flexed, semi-reclined, and reclined postures. We utilize geometric morphometric techniques, which are advantageous for evaluating shape variation and have not been extensively applied to biomechanical analyses. We found skeletal morphology to be significantly related to sex and height in all but the neutral posture (P < 0.05), and weight was marginally significantly related to shape in the semi-reclined posture (P = 0.047). Morphologically, male participants exhibited more flexion at the articulatio atlantooccipitalis than females, and females showed greater mandibular protrusion than males, although this result is likely related to height. No relationship was found between posture and TMD. This research establishes a framework for future work that uses geometric morphometric analyses to evaluate how neck postures vary in relation to TMD. Clin. Anat. 32:1061-1071, 2019. © 2019 Wiley Periodicals, Inc.

A comparison of biomechanical workload between smartphone and smartwatch while sitting and standing

Increasing concerns about musculoskeletal disorders in the upper back arising from excessive daily use of the smartwatch have been widely validated by the rising prevalence of discomfort. This study explored the smartwatch as a potential ergonomic intervention over the smartphone. Fourteen healthy participants completed five tasks (application setting, calling, message typing, message checking and vocal message entry) with smartphone and smartwatch in both sitting and standing postures. The neck-shoulder kinematics and muscle activation levels were monitored to assess the effects of the tasks, devices, and postures. The results indicated greater head flexion, head rotation and shoulder abduction and greater muscle activities for smartwatch use compared to smartphone use, but the performance measure (i.e., elapsed time) was superior for smartwatch use in all tasks except message typing. Collectively, only short and simple tasks such as message checking and application setting should be conducted with the smartwatch.

Naturalistic data collection of head posture during smartphone use

Association between smartphone use and head-down tilt posture has not yet been quantitatively evaluated in natural settings. This study aimed to objectively assess the angle and duration of head-down tilt posture of smartphone users during a typical working day via naturalistic data collection. Thirty-one college students conducted their typical school activities while their head posture and smartphone-app usage records were collected simultaneously for 8 hours. Participants spent 125.9 minutes (median usage duration) on their smartphones with significantly larger head-down tilt (p < .05) than when they were not using the phone. Head tilt angle greater than 30° was found to be more common when using the phone, while head tilt less than 20° was more common when they were not using the phone. Study findings provide empirical evidence that supports an association between the duration of smartphone use and the intensity of head-down tilt posture. Practitioner Summary: Head postures of young smartphone users were quantified for 8 hours continuously during a typical workday using a wearable sensor. Participants spent more time in larger head-down tilt postures (greater than 30°) when they were using their smartphones as compared to when they were not using them.

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

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

A radiographic investigation of cervical spine kinematics when reading a tablet in a reclined trunk position

The purpose of this study was to use radiographic measurements to compare cervical spine kinematics in various tablet computer reading postures. Radiographs were taken of twenty-two participants reading a tablet computer in five different postures. The lower cervical spine was more flexed in the semi-reclined (-8.2 ± 3.8°) and the reclined (-14.9 ± 4.0°) tablet positions compared to an upright (-4.43 ± 4.8°) tablet posture. Of the tablet reading positions, the reclined position had the lowest gravitational moment arm (5.2 ± 2.3 cm) and a skull angle closest to neutral (-9.4 ± 11.4°), while exhibiting the largest extension in the C1-C2 joint (34.4 ± 9.1°). Altering trunk position when reading a tablet could reduce the load required to support the head, but could put the head in a more forward head posture, stretch the cervical extensor muscles, and potentially result in pain.

High prevalence of inadequate sitting and sleeping postures: a three-year prospective study of adolescents

There is a paucity of information regarding the development of body posture during adolescence. This three-year prospective study aimed to evaluate sitting and sleeping postures among adolescents, and to determine whether these postures are associated with age and sex. We assessed 525 adolescents aged 11-16 years from the fifth to eighth grades. These adolescents were reassessed three years later. The Back Pain and Body Posture Evaluation Instrument was used to evaluate the sleeping posture and three sitting positions: sitting to write, to use a computer, and during leisure activities. Our findings indicated a low prevalence of adequate sleeping and sitting postures at baseline, with a decrease in prevalence observed after three years for all postures. These changes were similar for both sexes. Moreover, we found a strong reduction of adequate posture prevalence for younger adolescents, but the oldest adolescents demonstrated no significant differences after three years. Early, rather than late, adolescence is a critical period for establishing inadequate sitting and sleeping postures. This has implications for posture throughout adulthood; hence, interventions targeted at this age group are needed.