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

Abstract

BACKGROUND:

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

OBJECTIVES:

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

METHODS:

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

RESULTS:

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

CONCLUSION:

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

Keywords

Paediatrics forward head posture electronic media ergonomics screen viewing

1. Introduction

Poor posture during growth spurts is one of the key indicators for future health-related quality of life [1]. Electronic media became a mainstay of modern life, characterized by prolonged screen viewing time (SVT), especially in children [2]. Indeed, the percentage of children aged 0–8 years in the USA who own smartphones has nearly doubled from 38% to 72% over the last few years [3]. Likewise, Kabali et al. [4] examined an urban group of 350 children, finding that by age 4, three-quarters owned smartphones.

Prolonged smartphone use can lead to musculoskeletal problems. Neck, shoulder, and thumb pain are common in smartphone users, and their severity increases with prolonged duration of use [5]. Postural deviations such as forward head posture (FHP), slumped posture, or rounded shoulders are common end-results of prolonged smartphone use [6]. In addition, prolonged FHP posture has been associated with various musculoskeletal disorders of the cervical and lumbar spine [7].

Individuals using small-monitor devices such as smartphones and tablets usually gaze downward, which bends their head more than does use of desktop computers, which increases neck extensor and shoulder muscle activities [8]. Thus, correct posture and regular $\geqslant$ 20 min breaks are recommended when using smartphones, given that muscle fatigue and pain intensity worsen with prolonged smartphone use [9].

Children aged 8–14 years are at greater risk than adults for developing musculoskeletal problems because of increasingly earlier mobile phone use in children [10]. Nevertheless, 18.8% of adults over the age of 20 have been found to experience symptoms related to a musculoskeletal disorder from smartphone use, and that symptoms were exacerbated by prolonged duration of use [11]. Fatigue and pain of the upper trapezius muscle can be caused by the increased cervical flexion angle during smartphone use [12]. Moreover, prolonged smartphone usage can provoke changes in cervical and lumbar spine posture and proprioception in the cervical spine [13].

Smartphone addiction is characterized by daily use of prolonged durations. The percentage of adolescents and adults who use a smartphone for $>$ 4 h/day was reported to be 40% [14]. Individuals who use a smartphone for $>$ 4 h/day have been found to have problems in psychosocial functioning and increased rates of musculoskeletal abnormalities relative to smartphone users averaging $<$ 4 h/day of use [14]. A previous study has investigated the head, neck, and trunk angles in various smartphone use postures, finding that that head and neck flexion angles were elevated in all postures studied, with the highest head and neck flexion angles occurring when sitting without back support [15].

The posture of the cervicothoracic region is often affected by the position of the thoracolumbar region during sitting postures. The tonic labyrinthine and optical righting reflexes are responsible for maintaining the head vertical orientation during upright activities; these reflexes typically appear immediately at birth and persist throughout the lifespan. Keeping the head upright over the sacrum will successfully fix problematic head postures, which is a functional rather than structural modification. When the head is kept upright over the feet, all parts of the axial skeleton and lower extremities work together as parts of a closed chain; movement in one joint will produce movement in at least one additional link in the chain [16]. Motor activity and head, cervical, and thoracolumbar posture have a clear association with one another [17], and are affected by sitting and standing postures [18].

In a dynamic and rapidly evolving digital age, the negative health consequences of screen time remain an area of research interest, especially in pediatric populations. However, there are scarce data concerning factors associated with prolonged SVT, such as acceptable viewing duration, postural changes, and incidental effects on upper spinal posture. Therefore, we aimed to investigate the effects of SVT on head and neck posture during and after smartphone use in either a standing or sitting position. This may provide insight into effective strategies for minimizing the harmful effects of extended periods of mobile screen use in early and middle childhood.

2. Materials and methods

2.1 Participants

Participants were recruited through an advertisement posted for a duration of six months in two primary schools in Jeddah, Kingdom of Saudi Arabia. A total of 34 male children ranging from 5–12 years in age, met the inclusion criteria and were enrolled in the study. The study was approved by the Batterjee Medical College ethics review board (Res-2019-0023). The parents of children read and signed a consent form that complied with the Declaration of Helsinki. G*Power 3.1 software (University of Düsseldorf, Germany) was used for sample size calculation, with two-tailed comparisons of the difference between two independent means. The sample size was determined as 34 participants according to $\alpha=$ 0.05, power $=$ 0.80, and effect size $=$ 1.0.

Table 1
The demographic data of participants

	Group A (more than 4 hours), n:18 Mean $\pm$ SD	Group B (less than 4 hours), n:16 Mean $\pm$ SD	$p$ -value
Age, year	8.66 $\pm$ 1.79	8.29 $\pm$ 1.72	0.587
Height, cm	132.69 $\pm$ 8.50	131.71 $\pm$ 8.23	0.431
Weight, kg	30.88 $\pm$ 5.56	29.17 $\pm$ 5.64	0.762
BMI, kg/m ${}^{2}$	17.39 $\pm$ 1.22	16.66 $\pm$ 1.42	0.156
Duration, hours	6.06 $\pm$ 1.01	2.42 $\pm$ 1.06	0.001

Data are presented as mean $\pm$ standard deviation. Unpaired $t$ test: $p<$ 0.05 means significant difference.

Prospective participants were included if they had a minimum of six months of experience using smartphones, could follow the researcher’s instructions, and were physically active (at least 1 h of physical activity of moderate to vigorous intensity daily) [19]. They were excluded if they had any history of musculoskeletal or neurological disorders, back or neck pain, previous trauma or surgery to the neck region or the upper or lower extremities [2], involvement in a formal physical activity program, or were obese, according to the universal standard definition of child overweight and obesity, as the body mass index (BMI) cutoff point of overweight is 17.42–21.22 for boys between the ages of 5 and 12 years [20].

Based on parental reports, participants were classified into one of two groups depending on the number of hours spent daily using a smartphone: Group A comprised 18 children who averaged $>$ 4 h/day of smartphone use (6.06 $\pm$ 1.01 h), and group B comprised 16 children who averaged 1–4 h/day of use (2.42 $\pm$ 1.06 h) [21]. The demographic data of both groups are presented in Table 1.

2.2 Photography

A digital camera (Sony Alpha a6000 Mirrorless Digital Camera-24 MP) was used to capture a lateral photograph of each child. Kinovea software (which was used to evaluate the head and neck angles) is a reliable and valid tool for assessing the cervical range of motion (CROM) [22, 23]. Also, it is an accurate measurement tool at angles ranging from 45 ${}^{\circ}$ –90 ${}^{\circ}$ and distances up to 5 m [24].

Participants were told to adopt their typical sitting and standing postures during and after smartphone use. The camera was placed over the tripod at a distance of 80 cm from the child’s feet, while its height was adjusted according to the child’s height such that the camera was positioned perpendicular to the sagittal plane of the child’s external auditory meatus [25]. The tragus of the child’s ear, seventh spinous process (C7), and canthus of the eye were marked [26]. Participants adopted a natural standing and sitting position with their back unsupported for 20 min while browsing, gaming, or watching videos on their smartphone [2]. Digital photographs of the head and neck angles were analyzed with Kinovea software by independent physical therapists who were blinded to the purpose of the study.

2.3 Procedures

To assess head and neck postures, the following angles were examined: 1) the head flexion angle, which is the angle between a vertical line through the tragus of the ear and the line connecting the tragus and the lateral corner of the eye (canthus of the eye) [25]; 2) neck flexion angle, which is measured between a perpendicular line through C7 and another line from C7 to the tragus of the ear [25]; 3) craniocervical angle, which is formed by the intersection between two lines, the first connecting the tragus of the ear to the canthus of the eye, and the second joining the ear tragus to C7 [27]; and 4) the gaze angle, which lies between the line connecting the eye with the center of the smartphone screen and a horizontal line passing through the canthus [26, 28] (Fig. 1).

Figure 1.

Head flexion, neck flexion, craniocervical and gaze angles.

The majority of the post-fatigue recovery of the cervical spine occurs within the first 30 min. Approximately 79–95% of recovery occurred within the first 15 min, and a further 5–11% over the ensuing 15 min [29]. To assess any lasting effects after ceasing smartphone use, the same angles were re-photographed 30 min after ceasing phone use by using the same photographic procedures while sitting and standing without holding a smartphone. The order of standing or sitting positions was randomly selected to avoid familiarization effects. Three shots were taken, and the mean average was documented. Standing and sitting positions were conducted on two different days to avoid the effect of fatigue.

Table 2

The effect of smartphone using status (while using and after using it for 30 minutes) in standing and sitting positions

Table 3

The effect of body position on head and neck angles while using a smartphone and after using it for 30 minutes

2.4 Statistical analysis

Statistical Package for the Social Sciences v. 20.0 (SPSS; IBM Corp., Armonk, NY, USA) was used for data analysis. Unpaired $t$ -test was used to distinguish between age, height, and weight in both groups, while multivariate analysis of variance (MANOVA) was used to examine the effect of smartphone use duration and of body position on the head and neck angles. The level of significance with an alpha level of 0.05 was considered to be statistically significant with 95% confidence intervals.

3. Results

No statistically significant differences were found between groups in age, height, weight, and BMI ( $p>$ 0.05). The smartphone use duration of group A was significantly higher than that of group B ( $p<$ 0.05; Table 1).

3.1 Effect of smartphone use status

No significant differences were found in head flexion, neck flexion, craniocervical, and gaze angles while using a smartphone and 30 min after ceasing its use in group A in either a standing or sitting posture ( $p>$ 0.05). For group B, the head flexion, neck flexion, and gaze angles during smartphone use were significantly higher than 30 min after its use in either a standing or sitting posture, and the craniocervical angle during smartphone use was significantly lower than 30 min after its use in either a standing or sitting posture ( $p<$ 0.05; Table 3).

3.2 Effect of body position

In a sitting position, the values of head flexion, neck flexion, and gaze angles for both groups were significantly higher than when standing, both during and 30 min after smartphone use. However, the craniocervical angle in a sitting position was significantly lower than when standing, both during and 30 min after smartphone use ( $p<$ 0.05; Table 3).

3.3 Effect of smartphone use duration per day

The values of the head flexion, neck flexion, and gaze angles of group A were significantly higher than those of group B in either a sitting or standing position during and 30 min after smartphone use. Conversely, the craniocervical angle of group A was significantly lower than that of group B in both a sitting and standing position during and 30 min after smartphone use ( $p<$ 0.05; Tables 3 and 3).

4. Discussion

This study was conducted to assess the effects of prolonged SVT on head and neck posture in children during and after using a smartphone while assuming standing and sitting positions. The results indicated that using a smartphone, $<$ 4 h/day is associated with decreased head and neck flexion posture and eye gaze angle in both studied postures relative to those who average $>$ 4 h/day of smartphone use. Furthermore, the limited posture deviations that happened in the group using a smartphone, $<$ 4 h/day during phone use returned to the baseline resting posture within 30 min. These results can help develop realistic screen time exposure guidelines. The American Academy of Pediatrics recently loosened its guidelines, which previously recommended no more than 2 h/day of screen time for children aged 8–12 years. The amended guidelines no longer contain specific exposure duration guidelines, but do recommend at least 1 h of physical activity daily and 8–12 h of sleep, depending on age [30]. The current findings also emphasize the importance of posture during phone use in order to minimize the side-effects of excessive screen time.

Our data further revealed that using a smartphone for $>$ 4 h/day is significantly associated with increased the head and neck flexion posture while in a sitting and standing position, which can be attributed to fatigue of the trunk and neck muscles. The control of an erect posture while sitting and standing requires sustained activation of postural muscles to generate and maintain low levels of force necessary to counteract external forces (e.g., gravity). Coordinated activation of the trunk muscles has been considered necessary for maintenance of an upright posture with minimal postural sway or deviation [31]. Muscular fatigue may disturb the posture control by its adverse effects on the accuracy of sensory information, integration of peripheral afferents within the CNS, and efficacy of motor command recruitment [32]. Moreover, decreased proprioceptive accuracy of the trunk muscles following fatigue has been proposed as a potential contributor to fatigue-induced postural control deficits [33].

Overloading and fatigue of the neck extensors and shoulder muscles were reported during excessive screen viewing, as smartphone users tend to bend their heads more as they accommodate a relatively small screen size [34]. Consequently, the viewing distance to the smartphone becomes closer with time progression. As confirmed by the Kinovea software measurement, the viewing distance of group (A) was considerably smaller than group (B) in both sitting and standing. Long et al. [35] identified an inverse relationship between viewing time and viewing distance in previous research. Maximal muscle force has been shown to be lower in children than in adults, even when the size-normalized to muscle cross-sectional area [36]. This may explain why easy fatigability and consequent loss of postural control occurred after 4 h of smartphone use.

The results showed that the increase in the head, neck flexion, and gaze angles with a decrease of craniocervical angle during sitting is more pronounced than when standing in children who average $>$ 4 h/day of smartphone use. This is referred to as a static position, and when combined with an unsupported back and arms, could lead to abnormal alignment of the neck and shoulders. One of the potential risk factors for musculoskeletal disorders is a static and asymmetric position during smartphone use [37, 38]. The alterations in angles during sitting compared to standing could also be explained by the difference in the thoracolumbar posture between sitting and standing. The work of Claus et al. [39] has shown that after a 10-min computer task while sitting, spinal angles flexed 24 degrees at lumbar and 12 degrees at thoracolumbar regions relative to standing, which is mechanically compensated by increased head and neck flexion angles.

These results are consistent with those of D’Anna et al. [40] who studied the effect of different smartphone use durations on posture while sitting or standing, finding that neck angle variations were significantly higher when seated than when standing; suggesting that the alteration of the neck angle during smartphone usage may depend on the posture. Corroborating these results are the findings of Kuo et al. [15] who studied 41 healthy adults aged 18–25 years. They investigated the head, neck, and trunk angles in different postures during smartphone use, concluding that smartphone use increased the angles of the head and neck flexion in all positions, and that an unsupported sitting position resulted in greater head and neck flexion angles.

Regarding group comparisons, the results indicated that when the head and neck flexion are corrected 30 min after ceasing smartphone use, the head and neck flexion posture nonetheless remains higher in children averaging $>$ 4 h/day of use than the flexion posture of children averaging 1–4 h/day in either position. Using a smartphone for $>$ 3 h/day alters the kinematics of the neck and of the trunk [40]. Prolonged use of a smartphone could cause micro-trauma to the muscle fibers, leading to overactivity and accumulative damage to the muscles of the neck and shoulders [9].

These results align with those of Kim et al. [13], who concluded that prolonged smartphone use results in increased cervical and lumbar spine flexion angles relative to brief-duration smartphone use, a finding corroborated by Lee et al. [41], who found increased cervical angles in asymptomatic individuals while using a monitor in the workplace. Furthermore, the prolonged smartphone usage periods could result in more physical abnormalities [11]. In line with this result, Lee et al. [42] showed that neck flexion angle in the standing position was higher than when sitting on a chair or on the floor, and that neck flexion angle increases as smartphone duration use increases. Also, a decline in the sensory discrimination of neck positions was noticed during prolonged smartphone use [43].

Moreover, the present study reported that children averaging $>$ 4 h/day of smartphone use have a more flexed head and neck posture, even 30 min post-smartphone use, compared to children with less daily use, a conclusion also supported by Lee et al. [43], who reported a decline in the sensory discrimination of neck positions in individuals with prolonged smartphone use [44]. Furthermore, Kim et al. [13] found posture changes in the cervical and lumbar vertebrae as well as proprioception deficits in the neck region as a result of extended smartphone use. Moreover, severely phone-addicted individuals exhibited the greatest reposition error in the neck region [43]. Another explanation for the maintained flexed posture 30 min after smartphone use is muscle imbalance that develops into a posture disorder [45].

The increased flexed posture of the neck while sitting is verified by Shaghayegh Fard et al. [18] who described that the craniovertebral angle (CVA) while sitting is smaller than its normal value during standing in normal subjects and the forward FHP increases with lesser CVA. This suggests that individuals with a normal CVA while standing could be misdiagnosed in a seated position as FHP, which is consistent with the findings of Caneiro et al. [17] which showed that there is an association between motor activity and posture of the head, cervical and thoracolumbar regions. Therefore, postural changes in the thoracolumbar spine, create a feedback loop with the head and neck [16].

During the supported sitting position, the load on the lumbar spine is lighter than during sitting without support. In addition, backrests support some of the upper body’s weight, which decreases muscle activity and eases intra-disc pressure [46]. Shaghayegh Fard et al. [18] recommended assessing neck posture in a standing, rather than supported sitting position; this is based on evidence that posture changes occur during supporting sitting and induce FHP because the trunk and thoracic spine are pushed forward and the thoracic spine adopts a kyphotic posture [46]. In a supported sitting position, the head flexes during smartphone use and, for ideal vision, the head seeks the eye level and the cervical spine is extended when raising the head from the forward position, which caused greater FHP [47]. The deep cervical flexors act bilaterally and play a key postural role in straightening and stabilizing the cervical lordosis and in modulation intervertebral mobility [48, 49]. Therefore, decreasing the postural muscle activity during slumped sitting – unlike when standing – allows the cervical region to depend on the stability of the passive tissues of the vertebral column [50].

The current study found that children averaging $>$ 4 h/day of smartphone use have a more flexed head and neck in either sitting or standing positions relative to those averaging less daily use. These results are consistent with Shaghayegh Fard et al. [18] who showed a significant reduction in the CVA during sitting position compared to standing position, that was more noticeable in the normal group than the FHP group, even though their participants were adult, not children. This may denote that the severity of the FHP might be worsened by prolonged sitting posture and some of the postural changes may become permanent over time. Hence, sitting for prolonged periods of time could increase the likelihood of FHP. Most modern working environments require extended periods of sitting, which induces an inclined spine position, especially while working at a desk or on a computer.

The prolonged use of smartphone leads to slumped posture and rounded shoulders [6], which creates FHP in relation to the trunk, as the head was translated anteriorly and the lower cervical spine was flexed. The FHP may be associated with an increase in upper cervical extension [51], tightness of the cervical extensor muscles, the upper trapezius, the levator scapulae muscle, and the sternocleidomastoid muscle [52]. Rounded shoulders are a forward translation of the acromion relative to C7, and are usually accompanied with an abducted, anteriorly tilted and internally rotated scapula and shortening of the pectoralis minor muscle [53]. These posture deviations could explain the sustained flexed posture of the neck 30 min after ceasing smartphone use.

Although the aim of this study was achieved, namely characterizing the relationships between SVT and head and neck posture, some limitations should be considered. The participants were not randomly selected and all were male. Furthermore, this study’s small sample size limits the generalizability of the findings. Future research to better understand the relationship between muscle activity and biomechanical risks associated with long smartphone use durations could yield invaluable insights. More studies are needed to delineate the direct and indirect effects of smartphone use duration on the physical functioning or the strength of the upper extremities.

5. Conclusion

The findings of this study revealed that prolonged SVT is associated with increased neck and head flexion posture in children, especially in the sitting position. Parental awareness of smartphone use patterns in their children and of their postures during smartphone use is recommended to reduce the risk of developing musculoskeletal disorders. Further studies are encouraged to glean additional insight into the effects of brief periods of SVT (e.g., $<$ 4 h/day) and of alternating the screen viewing position (e.g., between sitting and standing positions) on the development of musculoskeletal disorders.

Footnotes

Conflict of interest

The authors have no conflict of interest to report.

Funding

This research did not receive any financial support.

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

Abstract

BACKGROUND:

OBJECTIVES:

METHODS:

RESULTS:

CONCLUSION:

Keywords

1. Introduction

2. Materials and methods

2.1 Participants

Table 1 The demographic data of participants

2.3 Procedures

3. Results

3.1 Effect of smartphone use status

3.2 Effect of body position

3.3 Effect of smartphone use duration per day

4. Discussion

5. Conclusion

Footnotes

Conflict of interest

Funding

References

Table 1
The demographic data of participants