Prolonged Standing-Induced Low Back Pain Is Linked to Extended Lumbar Spine Postures: A Study Linking Lumped Lumbar Spine Passive Stiffness to Standing Posture.

Postural assessments of the lumbar spine lack valuable information about its properties. The purpose of this study was to assess neutral zone (NZ) characteristics via in vivo lumbar spine passive stiffness and relate NZ characteristics to standing lumbar lordosis. A comparison was made between those that develop low back pain during prolonged standing (pain developers) and those that do not (nonpain developers). Twenty-two participants with known pain status stood on level ground, and median lumbar lordosis angle was calculated. Participants were then placed in a near-frictionless jig to characterize their passive stiffness curve and location of their NZ. Overall, both pain developers and nonpain developers stood with a lumbar lordosis angle that was more extended than their NZ boundary. Pain developers stood slightly more extended (in comparison to nonpain developers) and had a lower moment corresponding to the location of their extension NZ boundary. Overall, in comparison to nonpain developers, pain developers displayed a lower moment corresponding to the location of their extension NZ boundary which could correspond to greater laxity in the lumbar spine. This may indicate why pain developers have a tendency to stand further beyond their NZ with greater muscle co-contraction.

Musculoskeletal pain latent classes and biopsychosocial characteristics among emerging adults.

BACKGROUND: Emerging adults (aged 18-29) report high levels of musculoskeletal pain; however, it is unknown if body location and intensity patterns are related to different biopsychosocial characteristics. This study identified patterns of self-reported musculoskeletal pain among emerging adults and assessed if there were differences in their lifestyle and psychological characteristics. METHODS: Data from survey responses from a large public university and a large medical university in the United States were used (n = 1,318). Self-reported pain location and intensity at five body regions were assessed, and latent class analysis identified classes separately for men and women. Mental health, physical activity, and sleep outcomes were compared between the classes. RESULTS: Four classes were identified for men and women. Three of the classes were consistent between genders - "no pain," (women = 28% of their sample; men = 40% of their sample) "mild multisite pain," (women = 50%; men = 39%) and "moderate-severe multisite pain" (women = 9%; men = 7%). The fourth class for women was "moderate spine pain," (13%) and for men was "mild extremity pain" (13%). For both men and women, the "moderate-severe multisite" pain classes reported the highest levels of depression, anxiety, and stress, poorer sleep, and higher work physical activity than the "no pain" class. The "mild multisite" and "moderate spine" (women only) pain classes fell between the "no pain" and "moderate-severe" pain classes. The characteristics of the "mild upper extremity pain" class for men was similar to the "no pain" class. CONCLUSIONS: The identified classes provide unique information on pain location and intensity in emerging adults. The high prevalence of "mild multisite pain" (n = 593; 45% of the total sample) demonstrates an intervention opportunity during this age range to prevent further increases in musculoskeletal pain later in life. Future work should assess the longitudinal outcomes of these pain classes, the impact of interventions for this age group, and the balance between leisure and occupational physical activity when addressing musculoskeletal health.

Examining Potential User Experience Trade-Offs Between Common Computer Display Configurations.

OBJECTIVE: To determine how ultrawide (UW) and dual displays configurations can influence neck biomechanics and performance compared to a single display. BACKGROUND: Studies have assessed neck kinematics and performance when using dual displays, but these studies have used screen sizes smaller than today's display size, have inconsistent participant placement, and few have assessed these two variables together. METHODS: Seventeen participants completed five tasks on six display configurations. Neck kinematics and performance were tracked for each configuration. RESULTS: Centered configurations produced significantly different median neck rotation angles compared to secondary configurations (p < .001) for three of the tasks. A 34" curved UW display with a longer viewing distance produced similar neck kinematics to a single 24" display with the potential to also reduce screen interactions. When compared to single, the benefit of secondary versus centered monitors was dependent on the type of task being performed. Users may prefer the UW, centered dual, and secondary dual configurations over the single display. CONCLUSION: The benefit of secondary versus centered displays is dependent on the type of task being performed. Dual displays are still beneficial but should be used with a monitor arm to switch between centered and secondary configurations as necessary. Future work should look at larger UW displays to see if these results hold compared to dual display configurations. APPLICATION: The results can be used to make evidence-based guidelines for displays based on size and task. Researchers can use this information to design future studies looking at specific configurations.

Defining the lumbar and trunk-thigh neutral zone from the passive stiffness curve: application to hybrid sit-stand postures and chair design.

Minimal data exist on the neutral position for the lumbar spine, trunk, and thighs when adopting a hybrid posture. This study examined sex differences in the neutral zone lumbar stiffness and the lumbar and trunk-thigh angle boundaries of the neutral zone, and determined if the standing lumbar angle fell within the neutral zone. Passive lumbar flexion and extension moment-angle curves were generated for 31 participants (13 M, 18 F), pooled from two datasets, with trunk-thigh angles available for 10 participants. The neutral zone was defined as the low stiffness zone from both the flexion and extension curves. Males demonstrated significantly greater extensor stiffness. Neutral lumbar and trunk-thigh angles ranged on average -22.2 to 0.2° and 124.2 to 159.6° for males and -17.8 to -1.3° and 143.2 to 159.5° for females, respectively. Standing lumbar angles fell outside the neutral zone for 44% of participants. These neutral zone boundaries may inform kinematics for hybrid chair designs.Practitioner summary: Adoption of a neutral spinal posture may be achieved through hybrid chair design, yet minimal data exists on a physiologically defined neutral zone. Using measures of in vivo lumbar stiffness, the lumbar and trunk-thigh angular boundaries of the neutral zone were defined for both males and females.Abbreviations: EMG: electromyography; MVC: maximal voluntary contraction.

Does Using Multiple Computer Monitors for Office Tasks Affect User Experience? : A Systematic Review.

OBJECTIVE: To compare the impact of multiple computer monitor configurations on health and performance outcomes compared to the use of a single monitor. BACKGROUND: Multiple monitor configurations are used in office settings to promote increased productivity by providing more screen space; however, it is unknown if there are health-related trade-offs to increased productivity. METHOD: A systematic review was conducted according to the PRISMA statement guidelines and adapted the best evidence synthesis. RESULTS: Eighteen studies were included in our review. There was strong evidence that implementing dual monitors is in line with users' preference. There was also moderate evidence for controlled laboratory studies demonstrating that multiple monitors may increase task efficiency with decreased desktop interaction; however, implementing multiple monitors may also result in nonneutral neck postures for users. CONCLUSION: More research needs to be conducted on biomechanical exposures when using larger displays. Longitudinal field studies should be conducted to determine the influence of monitor interventions on health, productivity, and well-being. All studies must consider task complexity and user positioning and should measure health and productivity outcomes together. Researchers must also consider up-to-date purchasing trends when choosing the monitor configurations and sizes for their studies. APPLICATION: Regulatory bodies and practitioners can use the results to develop evidence-based monitor guidelines and inform decision-making in practice, respectively. Researchers can use this information to design future studies on monitor configurations that incorporate current purchasing trends.

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.

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.

Prolonged standing increases lower limb arterial stiffness.

PURPOSE: Standing workstations have recently been promoted as a healthy alternative to sitting. However, it is unknown how prolonged standing affects arterial stiffness, a prognostic indicator of cardiovascular health. The purpose of this study was twofold: to observe changes in arterial stiffness, as assessed by pulse wave velocity (PWV), with a 2-h bout of standing, and to determine if short, intermittent walking bouts provide a comparative advantage to standing alone. METHODS: Nineteen adults had arterial stiffness assessed by pulse wave velocity. Central (CPWV), upper peripheral (UPWV), and lower peripheral (LPWV) PWV were assessed before (supine), during standing (min 10, 60, and 120), and after (supine) the 2-h standing bout. In one trial, the participants stood at a standing desk immobile for 2 h. In the other trial, participants performed 5-min walking breaks after every 25 min of standing. RESULTS: After 2-h of standing, supine (85.8 ± 90.1 cm/s) and standing (303.4 ± 390.2 cm/s), LPWV increased independent of trial (i.e., main effect of time; p < 0.001). Walking breaks during 2 h of standing did not significantly attenuate these changes. In addition, standing CPWV decreased over time (- 38.5 ± 61.5 cm/s; p = 0.04). Yet, UPWV, standing or supine, did not change over the course of standing (p > 0.05). CONCLUSIONS: These findings indicate that prolonged standing increases the measures of arterial stiffness and there is no evidence that walk breaks attenuate this response.

Influence of Input Hardware and Work Surface Angle on Upper Limb Posture in a Hybrid Computer Workstation.

OBJECTIVE: We evaluated the effect of work surface angle and input hardware on upper-limb posture when using a hybrid computer workstation. BACKGROUND: Offices use sit-stand and/or tablet workstations to increase worker mobility. These workstations may have negative effects on upper-limb joints by increasing time spent in non-neutral postures, but a hybrid standing workstation may improve working postures. METHOD: Fourteen participants completed office tasks in four workstation configurations: a horizontal or sloped 15° working surface with computer or tablet hardware. Three-dimensional right upper-limb postures were recorded during three tasks: reading, form filling, and writing e-mails. Amplitude probability distribution functions determined the median and range of upper-limb postures. RESULTS: The sloped-surface tablet workstation decreased wrist ulnar deviation by 5° when compared to the horizontal-surface computer when reading. When using computer input devices (keyboard and mouse), the shoulder, elbow, and wrist were closest to neutral joint postures when working on a horizontal work surface. The elbow was 23° and 15° more extended, whereas the wrist was 6° less ulnar deviated, when reading compared to typing forms or e-mails. CONCLUSION: We recommend that the horizontal-surface computer configuration be used for typing and the sloped-surface tablet configuration be used for intermittent reading tasks in this hybrid workstation. APPLICATION: Offices with mobile employees could use this workstation for alternating their upper-extremity postures; however, other aspects of the device need further investigation.

The influence of a seated break on prolonged standing induced low back pain development.

With the recent attention to 'sitting disease', health practitioners and scientists are promoting standing in the workplace to decrease sedentary time, despite a high prevalence of low back pain (LBP) development during prolonged standing. The purpose of this study was to assess how a seated break inserted between bouts of prolonged standing would influence LBP development, posture and movement. A total of 20 participants stood for 45 minutes, sat for 15 minutes and repeated this sequence while lumbar and thoracic angles were measured, and LBP visual analogue scale reports were taken. Of the sample, 55% participants reported LBP in standing. A stand to sit ratio of 3:1 did not provide lasting recovery of LBP from standing and pain developers utilised a limited range of their lumbar spine angle and increased thoracic extension, resulting in static postures that caused tissue aggravation that was not resolved after 15 minutes of sitting. Prolonged standing in the workplace has the potential to result in LBP for some workers and alternate ways to reduce sedentary time should be investigated.

User experience with ultrawide curved displays: A mixed methods analysis.

Due to the trend of replacing dual displays with ultrawide (UW) curved displays, we used a mixed methods analysis to investigate the user experience with UW curved displays. We conducted an experimental laboratory study that quantified user self-selected positions for three displays - 24 in. flat panel, and 34 in. and 40 in. UW curved displays. Participants were first provided with a familiarization protocol, and they then positioned the display. The self-selected UW display viewing distances were within current recommendations; however, viewing distance increased with display size, potentially challenging small work surface depths and may have been in response to feeling "overwhelmed" by larger displays. Head twist range of motion increased with display width. While all displays were within recommendations, participants commented that less head twisting was a factor in choosing the 34 in. over the 40 in. display. Practitioners should assess potential workstation limitations and the potential impact on neck twist angles when installing ultrawide displays.

Relationships between grit, physical activity, and academic success in university students: Domains of physical activity matter.

ObjectiveTo examine the relationships between contexts of physical activity, grit, and GPA in a college population.Participants:875 Undergraduate students from a large, southern university participated between October 2018 and March 2020.Methods:Participants completed an electronic survey evaluating physical activity and grit. The university provided official GPAs. Multiple linear regression models evaluated the correlations between grit, the different physical activity domains, and GPA.Results:Grit was positively associated with domestic physical activity, leisure time physical activity, and GPA. Consistency of interest had no associations with the domains of physical activity or GPA. Perseverance of effort was positively associated with walking, active transport physical activity, domestic physical activity, leisure physical activity, and GPA.Conclusion:Perseverance of effort is related to different domains of physical activity and GPA. Future studies should investigate if increasing leisure time physical activity causes increases in perseverance of effort.

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.

TECHNICAL ABSTRACTBackground: People commonly use their phones with a flexed neck. Such use is concerning because epidemiological studies have demonstrated a direct relationship between prolonged neck flexion and neck pain, and mobile device use is associated with neck pain development.Purpose: Determine the repeatability of neck and upper back pain symptom development among young adults (ages 18-29) during 30-minutes of smartphone use with a flexed neck and compare neck flexion range of motion, neck extensor endurance, and posture among participants who develop neck and/or upper back pain during the task compared to those who do not develop pain.Methods: Participants (n = 40) came to the lab on two days separated by one week. They completed a 30-minute smartphone use trial with the device in their lap to elicit neck flexion. Participants were separated into pain groups based on a 10-mm change in their self-reported pain reports on a 100-mm visual analog scale (VAS). Pre-post tests and kinematics during the 30-minute trial were compared between individuals who did and did not consistently develop pain.Results: Seventy-five percent of the total study sample were categorized in the same pain category in the two trials using VAS score change. Of those participants, 66% developed neck pain during 30-minutes of smartphone use with sustained neck flexion. The most common symptom description was "aching." Pain developers had a lower cervical extensor test duration after 30-minutes of smartphone use than before smartphone use.Conclusions: Two-thirds of young adults developed consistent neck and/or upper back musculoskeletal pain that they described as aching after 30-minutes of smartphone use with sustained neck flexion. Since the nontraditional work environment may result in the use of these devices, employers will need to be aware of the potential consequences of sustained postures during mobile device use and develop methods to mitigate pain.

Anti-fatigue mats can reduce low back discomfort in transient pain developers.

Complaints of musculoskeletal pain are common among employees who stand for prolonged periods. This study sought to determine if an anti-fatigue mat (AFM) could uniquely affect low back pain (LBP), low back posture, and foot-floor interface responses in individuals prone to developing LBP (termed pain developers (PDs)) during prolonged standing experiments compared to those who do not develop LBP under the same exposures (termed non pain developers (NPDs)). Sixteen volunteers (8 PDs and 8 NPDs) were recruited based on their pain-development tendencies, which were established in previous standing experiments. They visited the laboratory on two separate days for 60 min of light manual work while standing on either a rigid floor or AFM. All participants were asymptomatic at the beginning of each experimental session. The amount of LBP experienced during the standing exposure, measured via a visual analogue scale, was reduced (p = 0.03) in the PD group when on the AFM (3.6 ± 6 mm) compared to the rigid floor (6.8 ± 7 mm). LBP levels remained low and unchanged (p = 0.5) between the AFM (2.4 ± 5 mm) and rigid floor (1.6 ± 2 mm) conditions for the NPD group. Neither postural nor foot-floor interface measures correlated with this unique reduction of LBP for the PD group when standing on the AFM. The AFM did, however, increase centre of pressure excursion (NPD 55% increase; PD 35% increase) and tended to increase the number of body weight shifts (NPD 116% increase; PD 54% increase) in both the PD and NPD groups. These findings suggest that AFMs may selectively benefit individuals prone to developing standing-induced back pain by facilitating subtle movements at the foot-floor interface.

Effects of anterior shear displacement rate on the structural properties of the porcine cervical spine.

While the individual tissues of the vertebral joint demonstrate viscoelastic properties, the global viscoelastic properties of the lumbar vertebral joint are not well established. This study investigated how changes in displacement rate influenced the mechanical response of the porcine cervical spine (a surrogate or model for the human lumbar spine) exposed to acute anterior shear failure loading. Thirty porcine cervical spine specimens (15 C3-C4 and 15 C5-C6) were placed under a 1600 N compressive load and subsequently loaded in anterior shear to failure at one of three randomly assigned displacement rates (1 mm/s, 4 mm/s, or 16 mm/s). Ultimate anterior shear force, ultimate displacement, average stiffness, and energy stored until failure were calculated. Load rate in the elastic region was also calculated to compare the load rates used in this study to those used in previous studies. Changes in displacement rate affected the C3-C4 and C5-C6 specimens differently. C5-C6 specimens tested at 16 mm/s had an ultimate force that was 28% and 23% higher than at 1 (p=0.0215) and 4 mm/s (p=0.0461), respectively. The average stiffness to failure of the C5-C6 specimens tested at 16 mm/s was 52% higher than at 4 mm/s (p=0.0289). No such differences were found for the C3-C4 specimens. An increase in the anterior shear displacement rate did not necessarily demonstrate viscoelasticity of the vertebral joint. Specimen intervertebral levels were affected differently by changes in anterior shear displacement rate, which may have been a result of anatomical and postural differences between the two levels. Future studies should further investigate the effect of displacement rate on the spine and the inconsistencies between different specimen levels.

Pain symptoms are reported earlier than quantitative measures of low back pain during prolonged standing.

BACKGROUND: Along with quantitative measures, pain symptoms may help inform early interventions to prevent prolonged standing induced low back pain (LBP); however, the relationship between quantitative and qualitative measures has not been assessed. OBJECTIVE: Determine the relationship between qualitative and quantitative measures of pain development during prolonged standing induced LBP development. METHODS: Thirty-five participants performed two-hours of standing. A visual analog scale (VAS) and the Short-Form McGill Pain Questionnaire were used to assess the participant's LBP every 7.5-minutes. Participants were classified as a pain developer (PD) based on VAS scores or three consecutive pain symptom reports. RESULTS: Pain symptom reports occurred 31.3 (±24.8) minutes earlier than the VAS reports. Eight participants (44%) were non-PDs with the VAS and PDs with the symptom method (p = 0.0047). CONCLUSIONS: A subset of participants who were not categorized as LBP developers during prolonged standing using the VAS method still report LBP symptoms. The inclusion of pain symptom reporting could provide additional information for practitioners when identifying individuals who would benefit from early interventions for standing induced LBP.

Low back pain development differentially influences centre of pressure regularity following prolonged standing.

Occupations requiring prolonged periods of static standing are associated with the development of low back pain (LBP). Certain individuals are susceptible to LBP development during prolonged standing (pain developers, PDs) while others are not (non-pain developers, NPDs). Linear centre of pressure (COP) measures suggest that standing balance control is negatively influenced following prolonged standing, and that PDs and NPDs may be differentially affected. The objective of this study was to determine if nonlinear standing balance control, quantified on COP, using sample entropy, is altered after 2-h of standing. Thirty two participants stood for 2-h. Separate 2-min standing trials, performed with eyes open and eyes closed, were collected before and after the 2-h standing protocol. Sample entropy, median power frequency and RMS amplitude of the COP time-series, was calculated from the 2-min standing trials for all participants. For comparison, participants were classified, post hoc, as PDs or NPDs according to visual analog scale pain scores. Sample entropy decreased after 2-h of standing for both PDs and NPDs, however, the decrease for NPDs was only 21% of the decrease observed in PDs. This study demonstrated that nonlinear control of upright standing changes after 2- hours of standing, resulting in an increase in COP regularity post 2- hours of standing for both PDs and NPDs. PDs displayed a greater change in COP regularity, which is supported by the theory that increased COP regularity occurs with pain/pathology.

Does proactive cyclic usage of a footrest prevent the development of standing induced low back pain?

Various interventions, such as standing intermittently with one leg on a footrest, have been suggested to prevent low back pain (LBP) development during prolonged standing. To assess this standing intervention twelve participants stood for 80 min while cycling through three minute periods of level-ground standing divided by one minute periods with either the right or left leg elevated onto a platform. All participants had previously participated in a prolonged level standing protocol and were classified as pain (PD) or non-pain developers (NPD). Out of the six known PDs, only one PD developed LBP by the end of the standing intervention. The intervals of elevated leg standing resulted in increased lumbar spine flexion in comparison to level standing. In addition, over time there was an increase in lumbar spine flexion during the level standing intervals. This change in lumbar spine posture in standing pain developers likely contributed to the reduced LBP development during this prolonged standing intervention.

Walking breaks can reduce prolonged standing induced low back pain.

Standing is commonly recommended to reduce sedentary behavior in the workplace; however, constrained prolonged standing has also been linked to musculoskeletal symptoms, such as low back pain (LBP). Light physical activity breaks, such as walking, may change lumbar spine posture enough to reduce LBP during standing. This study assessed the effectiveness of inserting 5-minute walking breaks every 25 min for reducing prolonged standing-induced LBP development. Nineteen participants completed two bouts of standing lasting 2 h - one with a 5-minute walking break every 25 min and one with no breaks. Pain measures were completed throughout the trial to categorize participants as pain developers (PDs) or non-pain developers (non-PDs). Lumbar region kinematics angle and range of motion were measured continuously. In standing, 58% (11/19) of participants were PDs, compared to just 26% when walking breaks were inserted. Seventy-three percent (8/11) were categorized as non-PDs with walking breaks. Median lumbar flexion increased during walking compared to standing. Lumbar region range of motion in the coronal and transverse planes also increased during walking. The intermittent lumbar flexion may help decrease LBP during prolonged standing. These results demonstrate that walking breaks may help promote lumbar movement and reduce prolonged standing-induced LBP.

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 ±â€¯3.8°) and the reclined (-14.9 ±â€¯4.0°) tablet positions compared to an upright (-4.43 ±â€¯4.8°) tablet posture. Of the tablet reading positions, the reclined position had the lowest gravitational moment arm (5.2 ±â€¯2.3 cm) and a skull angle closest to neutral (-9.4 ±â€¯11.4°), while exhibiting the largest extension in the C1-C2 joint (34.4 ±â€¯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.