Do different sitting postures affect spinal biomechanics of asymptomatic individuals?

Distribution of scoliosis in 2.22 million adolescents in mainland China: A population-wide analysis

Background

The characteristics of scoliosis afflicting school children and adolescents in mainland China are still unclear. Therefore, we conducted a systematic review to estimate scoliosis's prevalence and characterise its distribution in China.

Methods

We screened PubMed, Scopus, WanFang, China National Knowledge Infrastructure, National Science and Technology Library, and WeiPu databases for mainland China articles published between 1 January 1980 and 31 October 2022. Among them, we identified population-wide scoliosis studies in school children and adolescents. The main outcomes were the positive rate of primary screening and the prevalence of final screening. Primary screening mainly included general examination with/without the forward bending test in school. The final screening entailed clinical diagnosis by Röntgen radiation in a hospital (based on primary screening). A meta-analysis of scoliosis distribution by gender was performed to calculate the odds ratios (ORs) and 95% confidence intervals (CIs). Further, we analysed the distributions of scoliosis by age, region, aetiological type, and severity of curvature, in addition to the correlation between its prevalence and altitude or latitude.

Results

77 studies with 2 224 320 participants were included. The positive rate through primary screening was 3.97%, whereas the prevalence of scoliosis at final screening was 1.20%. Analysing the data revealed a higher prevalence of scoliosis in girls (OR = 1.57; 95% CI = 1.38-1.81). The age-wise peak rate of scoliosis was 15-16 years (1.07%) in boys and 13-14 years (1.42%) in girls. The mean prevalence of scoliosis was 1.07% in the western region, 1.54% in the central, and 1.35% in the eastern. Scoliosis prevalence was not correlated with either altitude or latitude. The prevalence of idiopathic and congenital scoliosis was 1.18 and 0.03%. Among all subjects with scoliosis, 79.10 and 16.80% had mild and medium disease severity.

Conclusions

According to this comprehensive study using data sets of scoliosis in adolescents across mainland China, the mean prevalence of scoliosis is 1.20%, yet 1.57 times higher in girls than boys, and is most prevalent in the middle region. Overall, scoliosis in adolescents could pose a burden to public health in mainland China.

Registration

PROSPERO CRD42021231987.

Work-Related Musculoskeletal Disorders in Endoscopic Sinus and Skull Base Surgery: A Systematic Review With Meta-analysis

OBJECTIVE

Endoscopic sinus and skull base surgery has led to significant improvements in patient outcomes, yet may have come at a cost to surgeons' musculoskeletal (MSK) health. We aimed to determine the prevalence and characteristics of work-related MSK disorders (WRMDs) in endoscopic sinus and skull base surgeons; to investigate contributing factors for WRMD in this population; and to evaluate the effectiveness of ergonomic interventions on the severity or prevalence of WRMD in this population.

DATA SOURCES

Medline, Embase, CINAHL, Web of Science, and Scopus from inception to April 2, 2024. A bibliographic examination was performed for further papers.

REVIEW METHODS

Inclusion criteria included original peer-reviewed papers with work-related MSK outcomes (prevalence, contributing factors, and interventions) relating to endoscopic sinus and/or skull base surgeons in any language.

RESULTS

Of 25,772 unique citations, 37 studies met the inclusion criteria. The pooled lifetime, point, and 12-month prevalences of WRMD were 75.9% (95% confidence interval; I2, 67.2%-83.6%, I2 95.6%), 80.8% (77.0%-84.3%, I2 98.0%), and 82.0% (71.8%-90.3%, I2 60.96%) respectively. The neck, lumbar spine, and thoracic spine were the most commonly involved areas. One of 9 studies on contributing factors investigated discomfort as an outcome. The remainder focussed on surrogate outcomes (eg, posture, hand dysfunction). Two of the 13 intervention studies investigated pain or fatigue as an outcome. The remainder targeted posture, muscle activity, or workload.

CONCLUSION

WRMDs are highly prevalent in endoscopic sinus and skull base surgeons. Further studies focusing on the direct outcomes of WRMD such as pain are needed.

Assessing the Preservation of Lumbar Lordotic Curvature in Everyday Sitting Conditions Assessed with an Inertial Measurement System

Background/Objectives: Lumbar lordotic curvature (LLC), closely associated with low back pain (LBP) when decreased, is infrequently assessed in clinical settings due to the spatiotemporal limitations of radiographic methods. To overcome these constraints, this study used an inertial measurement system to compare the magnitude and maintenance of LLC across various sitting conditions, categorized into three aspects: verbal instructions, chair type, and desk task types. Methods: Twenty-nine healthy participants were instructed to sit for 3 min with two wireless sensors placed on the 12th thoracic vertebra and the 2nd sacral vertebra. The lumbar lordotic angle (LLA) was measured using relative angles for the mediolateral axis and comparisons were made within each sitting category. Results: The maintenance of LLA (LLAdev) was significantly smaller when participants were instructed to sit upright (-3.7 ± 3.9°) compared to that of their habitual sitting posture (-1.2 ± 2.4°) (p = 0.001), while the magnitude of LLA (LLAavg) was significantly larger with an upright sitting posture (p = 0.001). LLAdev was significantly larger when using an office chair (-0.4 ± 1.1°) than when using a stool (-3.2 ± 7.1°) (p = 0.033), and LLAavg was also significantly larger with the office chair (p < 0.001). Among the desk tasks, LLAavg was largest during keyboard tasks (p < 0.001), followed by mouse and writing tasks; LLAdev showed a similar trend without statistical significance (keyboard, -1.2 ± 3.0°; mouse, -1.8 ± 2.2°; writing, -2.9 ± 3.1°) (p = 0.067). Conclusions: Our findings suggest that strategies including the use of an office chair and preference for computer work may help preserve LLC, whereas in the case of cueing, repetition may be necessary.

Effect of a slump posture on pain, proprioception, and electrical activity of the muscles in office workers with chronic non-specific neck pain. A retrospective study

BACKGROUND

The impact of computer typing in a slump posture on pain, proprioception and muscle recruitment has not been extensively investigated. Therefore, the purpose of this study was to evaluate the extent of pain, proprioception and muscle activity resulting from computer typing in a slump posture in women who already suffer from chronic neck pain.

METHODS

This cross-sectional study was conducted between May 20 to July 10, 2021. A total of 15 female 42-(±4.96)-year-old office workers with chronic non-specific neck pain participated in this study. Before and after 60 min of computer typing in a slump posture, proprioception and pain were measured using an inclinometer and visual analog scale (VAS), respectively. The activity of the cervical erector spine (CES) and upper trapezius (UT) muscle was also measured before and after the slump-posture computer typing, in upright, forward, and slump postures. RESU: lts: Paired-samples t-tests showed that pain was increased and proprioception in all directions (flexion, extension, right and left lateral flexion, and right, and left rotation) was less accurate (P < 0.05) after 60 min computer typing. The CES and UT muscle activity were elevated more in the forward head and slump posture than in the upright posture (P < 0.05).

CONCLUSION

Sixty minutes computer typing in a slump posture increased neck pain, resulted in a decreased proprioception in the neck and was accompanied by an increased activity of the neck musculature.

Don't Just Stand There. Rethinking the Ideal Body Posture for Otorhinolaryngologists

Surgeons have a high rate of work-related musculoskeletal injuries; an area that has received little attention. These injuries result in surgeons performing less efficiently, needing to take time off work, suffering higher rates of burnout, and may ultimately lead surgeons to retire earlier than planned. Otorhinolaryngologists are at particular risk for work-related musculoskeletal injuries. Beyond the clinician, sustaining such injuries can negatively impact patient safety. Ergonomic interventions have been used effectively to reduce work-related musculoskeletal injuries in other professions, yet not in surgery. With traditional teachings of ideal body postures to avoid injury and manual handling training being re-evaluated, it is important to explore evidence based interventions for reducing work-related musculoskeletal injuries in otorhinolaryngologists. New research encourages us to shift the focus away from the traditional one-size-fits-all approach to ergonomics and toward postural recommendations and education that promote a dynamic, individualized approach to avoiding sustained, static and awkward postures.

Biomechanical response of lumbar intervertebral disc in daily sitting postures: a poroelastic finite element analysis

This study aims to establish and validate a poroelastic L4-L5 finite element model to evaluate the effect of different sitting postures and their durations on the mechanical responses of the disc. During the sustained loading conditions, the height loss, fluid loss and von-Mises stress gradually increased, but the intradiscal pressure decreased. The varying rates of aforementioned parameters were more significant at the initial loading stage and less so at the end. The predicted values in the flexed sitting posture were significantly greater than other postures. The extended sitting posture caused an obvious von-Mises stress concentration in the posterior region of the inter-lamellar matrix. From the biomechanical perspective, prolonged sitting may pose a high risk of lumbar disc degeneration, and therefore adjusting the posture properly in the early stage of sitting time may be useful to mitigate that. Additionally, upright sitting is a safer posture, while flexed sitting posture is more harmful.

Biomechanical Effects of Different Sitting Postures and Physiologic Movements on the Lumbar Spine: A Finite Element Study

This study used the finite element method(FEM) to investigate how pressure on the lumbar spine changes during dynamic movements in different postures: standing, erect sitting on a chair, slumped sitting on a chair, and sitting on the floor. Three load modes (flexion, lateral bending, and axial rotation) were applied to the FEM, simulating movements of the lumbar spine. Results showed no significant difference in pressure distribution on the annulus fiber and nucleus pulposus, representing intradiscal pressure, as well as on the cortical bone during movements between standing and erect sitting postures. However, both slumped sitting on a chair and sitting on the floor postures significantly increased pressure on the nucleus pulposus, annulus fibrosus, and cortical bone in all three movements when compared to standing or erect sitting on a chair. Notably, sitting on the floor resulted in even higher pressure on the nucleus pulposus and annulus fibers compared to slumped sitting on a chair. The decreased lumbar lordosis while sitting on the floor led to the highest increase in pressure on the annulus fiber and nucleus pulposus in the lumbar spine. In conclusion, maintaining an erect sitting position with increased lumbar lordosis during seated activities can effectively reduce intradiscal pressure and cortical bone stress associated with degenerative disc diseases and spinal deformities.

Significance of Lower Body Postures in Chair Design

OBJECTIVE

This study examined a system-level perspective to investigate the changes in the whole trunk and head postures while sitting with various lower extremity postures.

BACKGROUND

Sitting biomechanics has focused mainly on the lumbar region only, whereas the anatomy literature has suggested various links from the head and lower extremity.

METHOD

Seventeen male participants were seated in six lower extremity postures, and the trunk kinematics and muscle activity measures were captured for 5 s.

RESULTS

Changes in the trunk-thigh angle and the knee angle affected the trunk and head postures and muscle recruitment patterns significantly, indicating significant interactions between the lower extremity and trunk while sitting. Specifically, the larger trunk-thigh angle (T135°) showed more neutral lumbar lordosis (4.0° on average), smaller pelvic flexion (1.8°), smaller head flexion (3.3°), and a less rounded shoulder (1.7°) than the smaller one (T90°). The smaller knee angle (K45°) revealed a more neutral lumbar lordosis (6.9°), smaller pelvic flexion (9.2°), smaller head flexion (2.6°), and less rounded shoulder (2.4°) than the larger condition (K180°). The more neutral posture suggested by the kinematic measures confirmed significantly less muscular recruitment in the trunk extensors, except for a significant antagonistic co-contraction.

CONCLUSION

The lower and upper back postures were more neutral, and back muscle recruitment was lower with a larger trunk-thigh angle and a smaller knee angle, but at the cost of antagonistic co-contraction.

APPLICATION

The costs and benefits of each lower extremity posture can be used to design an ergonomic chair and develop an improved sitting strategy.

Effects of Using a Shoulder/Scapular Brace on the Posture and Muscle Activity of Healthy University Students during Prolonged Typing-A Randomized Controlled Cross-Over Trial

Laptop use appears to contribute to poor working postures and neck pain among university students. Postural braces have the potential to improve upper back/neck posture and therefore might have a role as an ergonomic aid for this population. Therefore, the purpose of this study was to assess the short-term effects of scapular bracing on pain, fatigue, cervicothoracic posture, and the activity of the neck and upper-back muscles in healthy college students. A randomized controlled crossover trial was conducted to evaluate the self-reported pain and fatigue, the amplitude and median frequency of surface electromyography in neck extensors, upper trapezius, and lower trapezius, as well as the neck and shoulder sagittal alignment (measured by inertial sensors and digital photographs) during a 30-min typing task in a sample of young, healthy university students with or without a scapular brace. The brace condition resulted in significantly smaller levels of bilateral trapezius muscle activity (p < 0.01). Rounded shoulder posture was slightly better in the brace condition, but these differences were not significant (p > 0.05). There were no significant immediate differences in pain or fatigue scores, neck alignment, or the electromyographic activity of the other muscles tested between brace and non-brace conditions (all p > 0.05). However, bracing appears to immediately reduce the electromyographic activity of the lower trapezius muscles (p < 0.05). These findings shed some light on the possible advantages of scapular bracing for enhancing laptop ergonomics in this group of individuals. Future studies are warranted to evaluate the effects of different types of braces, the importance of matching the brace to the user, and the short- and long-term effects of brace use on computer posture and muscle activity.

The effects of Pilates exercise in comparison to other forms of exercise on pain and disability in individuals with chronic non-specific low back pain: A systematic review with meta-analysis

OBJECTIVE

To compare the effects of Pilates exercise (PE) with other forms of exercise on pain and disability in individuals with chronic non-specific low back pain (CNSLBP) and to inform clinical practice and future research.

STUDY DESIGN

Systematic review with meta-analysis conducted and reported in line the Preferred Reporting Items for Systematic review and Meta-analysis.

LITERATURE SEARCH

Six electronic databases were searched from inception to April 2021.

STUDY SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing the effect of PE with other forms of exercise for adults with CNSLBP on pain and disability.

DATA SYNTHESIS

Two reviewers assessed the risk of bias of the trials, guided by the Cochrane RoB2 tool. Available data were extracted for meta-analysis with subgroup analysis. Pilates exercise was compared to general exercise (GE), direction-specific exercise (DSE) and spinal stabilisation exercise (SSE). Certainty of evidence was interpreted following the Grading of Recommendations Assessment, Development and Evaluation approach.

RESULTS

Eleven RCTs were included. A low certainty of evidence supported PE was more effective than GE in pain reduction [Effect size (ES) 0.44]. Moreover, very low levels of certainty were revealed for effectiveness of PE compared with DSE for pain reduction (ES 0.65) and equivalence of PE and SSE for pain and disability.

CONCLUSIONS

This review found no strong evidence for using one type of exercise intervention over another when managing patients with CNSLBP. Existing evidence does not allow this review to draw definitive recommendations. In the absence of a superior exercise form clinicians should work collaboratively with the patient, using the individual's goals and preferences to guide exercise selection. Further appropriately designed research is warranted to explore this topic further.

Dose-response relationship between daily screen time and the risk of low back pain among children and adolescents: a meta-analysis of 57831 participants

BACKGROUND

The risk of low back pain (LBP) increases steeply during adolescence, and adolescents with LBP are more likely to have low back pain in their adult years. This study aimed to investigate the dose-response relationship between daily screen time and the risk of low back pain among children and adolescents.

METHODS

PubMed, the Cochrane Library, Embase, and Web of Science were searched to collect relevant studies on daily screen time and the risk of low back pain from the establishment of the database up to December 2022. Two investigators independently screened the literature, extracted data, and evaluated the risk of bias in the included studies. Stata16.0 was used to perform a dose-response meta-analysis and the methodological quality evaluation of the included studies.

RESULTS

The results of the meta-analysis showed that there is a positive correlation between daily computer time (OR = 1.32, 1.05-1.60), daily mobile phone time (OR = 1.32, 1.00-1.64), daily TV watching (OR = 1.07, 1.04-1.09) and the risk of low back pain, separately. The dose-response meta-analysis showed that there is a linear relationship between daily computer use and low back pain. The risk of low back pain increased by 8.2% for each 1-hour of daily computer use.

CONCLUSIONS

Screen time is related to the risk of low back pain, and there is a linear relationship between daily computer use and the risk of low back pain. A number of strategic measures should be taken to prevent adolescents from developing severe low back pain.

Recommended maximum holding time of common static sitting postures of office workers

PURPOSE

A posture maintained for a long period can be harmful to the health of office workers. This study aimed to estimate the recommended ergonomic duration for maintaining different sitting postures.

MATERIALS AND METHODS

Forty healthy male and female students participated in this experiment designed to measure perceived discomfort caused by maintaining common static sitting postures of office workers in a simple ergonomic setup for four minutes. The Borg CR10 scale was given to the participants to assess the discomfort in different body parts, before and after each experiment. Based on the mean group discomfort level of 2, the recommended holding time of each posture was estimated.

RESULTS

The recommended holding time and its discomfort score for each studied posture were tabulated. The shortest holding time of a posture was obtained for the moderate neck flexion (1.61 minutes), and the longest holding time was obtained for legs posture with 90-degree knee flexion (6.45 minutes).

CONCLUSIONS

The recommended holding time in this study may help to assess the risk of Musculoskeletal Disorders in office workers and train the individuals involved in office tasks in proper sitting behavior.

Associated Risk Factors with Low Back Pain in White-Collar Workers-A Cross-Sectional Study

Objective: The purpose of the study was to compare the pressure pain threshold (PPT) of soft tissue and the curvatures of the spine in a sitting position and to estimate associated physical risk factors with low back pain (LBP) in young adults. Subjects: White-collar workers (n= 139), both women (n = 51) and men (n = 88) were separated into a control group (n = 82) and a low-intensity LBP (NRS < 3) (n = 57). Methods: The PPTs were tested utilizing the Wagner algometer. The curvatures of the spine were measured employing the photogrammetric method. In the logistic regression model, the odds ratio (OR) was estimated with ±95% confidence interval (CI) indicating the probability of the reported LBP. Results: The PPTs of soft tissue (OR = 1.1; CI = 1.02−1.19; p < 0.05) and the angle of the thoracolumbar spine in the everyday, habitual sitting position (OR = 1.19; CI = 1.05−1.34; p < 0.05) were associated with low-intensity LBP in female subjects. Additionally, the low intensity LBP were associated with the angles of the torso (OR = 1.14; CI = 1.01−1.29; p < 0.05) and the lumbosacral spine in the corrected sitting position (OR = 1.06; CI = 0.98−1.15; p > 0.05) and BMI (OR = 1.56; CI = 0.84−2.90; p > 0.05) in male subjects. Conclusion: Individual risk factors were associated with the low-intensity LBP only in females utilizing the PPT and the thoracolumbar angle in the habitual sitting position study factors. Men from the LBP group did not effectively correct the lumbosacral angle. Therefore, re-educated, self-corrected posture with specific postural training would be expected to improve proprioception in postural control capacity and result in decreasing pain.

Investigation of office workers' sitting behaviors in an ergonomically adjusted workstation

Objectives. Common ergonomic office workstations are designed for a few optimum postures. Nonetheless, sitting is a dynamic activity and the ideal sitting posture is rarely maintained in practice. Therefore, the present study aimed to investigate the sitting behavior of office workers in an actual working environment using ergonomically adjusted workstations to examine whether they promote maintaining appropriate sitting postures. Methods. Sitting behaviors (frequency of postures and position changes in different body parts) were explored among 26 office workers during a 60-min sitting duration, using the posture recording and classification method developed by Graf et al. The rapid upper limb assessment (RULA) method was also used to assess postural load. Then, the results of the RULA method were compared with the results from investigating the sitting behavior of office workers. Results. Common ergonomic workstations were effective in eliminating some awkward postures. However, some important risk factors such as holding postures with an inappropriate lumbar spine curve (86% of the observations) and maintaining a posture for a long time (for 7-12 min) were observed in the participants' sitting behaviors, while they were neglected in the RULA method. Conclusions. The common ergonomic workstations could not guarantee the users' appropriate sitting behaviors.

Effects of the Multidimensional Treatment on Pain, Disability, and Sitting Posture in Patients with Low Back Pain: A Randomized Controlled Trial

The purpose of this study was to investigate the effects of multidimensional approach model on the pain, disability, and sitting posture in patients with nonspecific low back pain (LBP). Sixty LBP patients were recruited and were randomly divided into two groups: multidimensional treatment (MT) group (n = 30) and unimodal treatment (UT) group (n = 30). All participants underwent 48 sessions of treatment (40 min/session, two sessions per day, 2 days per week) for 12 weeks. The MT group conducted a core stability exercise twice a day and additionally provided training on pain principles and management methods. The UT group only performed a core stability exercise twice a day. The visual analog scale (VAS) and Oswestry Disability index (ODI) were used to measure pain intensity and disability. Thoracolumbar kyphosis and lumbar lordosis in the sitting position were measured using a motion capture system. After training, the pain and disability in the MT group improved significantly greater than the UT group (p < 0.05). In the MT group, the pain relief effect persisted 3 months after the end of training. Thoracolumbar kyphosis and lumbar lordosis in the MT group were significantly improved compared to the UT group (p < 0.05). Thus, MT combined with core stability exercise may be used to improve the pain, disability, and sitting posture in patients with LBP.

Lumbopelvic sagittal standing posture associations with anthropometry, physical activity levels and trunk muscle endurance in healthy adults

Background

Various factors, inherited and acquired, are associated with habitual spinal postures.

Objective

The purpose of this study was to identify the relationships between trunk muscle endurance, anthropometry and physical activity/inactivity and the sagittal standing lumbopelvic posture in pain-free young participants.

Methods

In this study, 112 healthy young adults (66 females), with median (IQR) age of 20 years (18.2-22 years), without low back pain, injury or trauma were included. Lumbar curve (LC) and sacral slope (SS) angles were measured in standing with a mobile phone application (iHandy level). Anthropometric, physical activity/inactivity levels (leisure-time sport involvement and sitting hours/day) and abdominal (plank prone bridge test) and paraspinal (Sorensen test) isometric muscle endurance measures were collected.

Results

LC and SS angles correlated significantly ( r = 0 . 80 , p < 0 . 001 ). Statistically significant differences for both LC ( p = 0 . 023 ) and SS ( p = 0 . 013 ) angles were identified between the male and female participants. A significant negative correlation was identified between the abdominal endurance time and LC ( r =- 0 . 27 , p = 0 . 004 ); however, the power of this result (56%) was not sufficiently high. The correlation between abdominal endurance and SS was non-significant ( r =- 0 . 17 , p = 0 . 08 ). In addition, no significant associations were identified between either of the sagittal lumbopelvic angles (LC-SS) in standing and the participants' body mass index (BMI), paraspinal endurance, leisure-time sport involvement or sitting hours/day.

Conclusion

The potential role of preventive exercise in controlling lumbar lordosis via enhancement of the abdominal muscle endurance characteristics requires further confirmation. A subsequent study, performed in a larger population of more diverse occupational involvement and leisure-time physical activity levels, is proposed.

Monitoring of Sitting Postures With Sensor Networks in Controlled and Free-living Environments: Systematic Review

BACKGROUND

A majority of employees in the industrial world spend most of their working time in a seated position. Monitoring sitting postures can provide insights into the underlying causes of occupational discomforts such as low back pain.

OBJECTIVE

This study focuses on the technologies and algorithms used to classify sitting postures on a chair with respect to spine and limb movements, using sensors and wearables such as inertial measurement units, pressure or piezoresistive sensors, accelerometers or gyroscopes, combined with machine learning approaches.

METHODS

A total of three electronic literature databases were surveyed to identify studies classifying sitting postures in adults. Quality appraisal was performed to extract critical details and assess biases in the shortlisted papers.

RESULTS

A total of 14 papers were shortlisted from 952 papers obtained after a systematic search. The majority of the studies used pressure sensors to measure sitting postures, whereas neural networks were the most frequently used approaches for classification tasks in this context. Only 2 studies were performed in a free-living environment. Most studies presented ethical and methodological shortcomings. Moreover, the findings indicate that the strategic placement of sensors can lead to better performance and lower costs.

CONCLUSIONS

The included studies differed in various aspects of design and analysis. The majority of studies were rated as medium quality according to our assessment. Our study suggests that future work for posture classification can benefit from using inertial measurement unit sensors, since they make it possible to differentiate among spine movements and similar postures, considering transitional movements between postures, and using three-dimensional cameras to annotate the data for ground truth. Finally, comparing such studies is challenging, as there are no standard definitions of sitting postures that could be used for classification. In addition, this study identifies five basic sitting postures along with different combinations of limb and spine movements to help guide future research efforts.

Differences in oscillometric blood pressure readings between unsupported and supported back conditions

Appropriate body posture is important for accurate blood pressure (BP) measurement. However, the impact of an unsupported back on BP readings is currently controversial. This study included 224 subjects (18-86 years old, 54.5 ± 15.5 years old, 105 males). BP was measured with an oscillometric BP device randomly following one of two protocols for back support conditions: (1) supported-unsupported-supported-unsupported, or (2) unsupported-supported-unsupported-supported. The average of the two systolic BP (SBP) and diastolic BP (DBP) readings in the same position was recorded as the final BP value. The differences in BP between the unsupported and supported back conditions were calculated as delta BP. Moreover, the percentage variation in BP (PV) was calculated with the formula delta BP/BP with an unsupported back. Multivariable regression analysis evaluated the impact of age, sex, hypertension history and supported BP level on PV. The SBP/DBP levels measured with an unsupported back were slightly higher than those when the back was supported (132.7 ± 19.5/79.6 ± 12.9 mmHg vs. 130.3 ± 20.0/78.5 ± 14.3 mmHg), and the delta SBP (2.3 mmHg) was statistically significant. The multivariable regression analysis showed that age was a positive factor but supported SBP level as a negative factor for systolic PV, while age and supported DBP level were positive factors, but hypertension history was a negative factor for diastolic PV. For a group participant, the mean difference in oscillometric SBP/DBP in the unsupported back position was 2.3/1.0 mmHg higher than that in the supported back position.

Effects of Prolonged Sitting with Slumped Posture on Trunk Muscular Fatigue in Adolescents with and without Chronic Lower Back Pain

Background and Objectives: This study investigated the effects of prolonged sitting on trunk muscular fatigue and discomfort in participants with and without chronic lower back pain (LBP). Material and Methods: This study included 15 patients with LBP and 15 healthy controls. All participants were instructed to sit on a height-adjustable chair with their knee and hip joints bent at 90° for 30 min, in slumped sitting postures. Surface electromyography was used to assess the median frequency of the internal obliques (IO)/transversus abdominis (TrA) and multifidus (MF) muscles. Perceived discomfort was measured using a Borg category ratio-scale. Median frequency of the trunk muscles and perceived discomfort after 30 min of sitting were compared with baseline. Result: There were no significant differences within the group and between both groups in the median frequency of bilateral IO and MF muscles. The LBP group showed significantly greater perceived discomfort after prolonged sitting, as compared to the control group. Conclusions: Prolonged sitting with slumped posture could increase the risk of experiencing lower back discomfort.

Differences in Proprioception Between Young and Middle-Aged Adults With and Without Chronic Low Back Pain

Introduction: While young adults with chronic low back pain (CLBP) exhibit impaired lumbar proprioception, it remains unclear if the same phenomenon is observed in middle-aged adults with CLBP. Objectives: This study aimed to investigate whether young or middle-aged adults with CLBP displayed different proprioception ability as compared to age-matched asymptomatic controls. Methods: Sixty-four young adults with [median age:34 [interquartile range (IQR): 29-37] years] and without [median age:29 (IQR; 23-34) years] CLBP, and 87 middle-aged adults with [median age:53 (IQR: 49-58) years] and without [median age: 54 (IQR: 45-64) years] CLBP underwent postural sway tests on a force-plate with (unstable surface) and without a foam (stable surface), while bilateral L5/S1 multifidi and triceps-surae were vibrated separately. An individual's proprioception reweighting ability was estimated by relative proprioceptive reweighting (RPW). Higher RPW values indicate less reliance on lumbar multifidus proprioceptive signals for balance. Participants also underwent lumbar repositioning tests in sitting to determine repositioning errors in reproducing target lumbar flexion/extension positions. Results: Young adults with CLBP demonstrated significantly higher median RPW values than age-matched asymptomatic controls for maintaining standing balance [stable surface: CLBP: 0.9 (IQR: 0.7-0.9), asymptomatic: 0.7 (IQR: 0.6-0.8), p < 0.05; unstable surface: CLBP: 0.6 (IQR: 0.4-0.8), asymptomatic: 0.5 (IQR: 0.3-0.7), p < 0.05]. No significant differences in repositioning error were noted between young or middle-aged adults with and without CLBP (p > 0.05). RPW values were unrelated to repositioning errors in all groups (p > 0.05). Conclusion: Young adults with CLBP, and middle-aged adults with and without CLBP had inferior proprioceptive reweighting capability. This finding may indicate potential age-related deterioration in central and peripheral processing of lumbar proprioceptive signals. Future studies should use advanced imaging and/or electroencephalogram to determine mechanisms underlying changes in proprioceptive reweighting in middle-aged adults.

Association of Exposures to Seated Postures With Immediate Increases in Back Pain: A Systematic Review of Studies With Objectively Measured Sitting Time

OBJECTIVE

The purpose of this study was to conduct a systematic review of studies to determine whether sitting time measured objectively (by laboratory controlled time trial, direct observation, or wearable sensor) is associated with the immediate increase in low back pain (LBP) (determined by pain scale rating) in people >18 years of age.

METHODS

Four databases (PubMed, EMBASE, SPORTDiscus, and Cumulative Index to Nursing and Allied Health Literature) were searched from inception to September 1, 2018. Randomized controlled trials and cohort and cross-sectional studies, where objectively measured sitting time was temporally matched with a measure of LBP in adults, were included. Studies without a control session conducted on a separate day were excluded. Screening, full-text review, data extraction, and risk of bias assessment (Quality In Prognosis Studies) of included papers were performed independently by 2 reviewers, with a third available to resolve disagreements.

RESULTS

In total, 609 articles were identified, 361 titles/abstracts were screened,75 full-text articles were assessed for eligibility, and 10 met the inclusion criteria. All but 1 reported sitting time to be associated with an immediate increase in LBP. Six of these reported clinically relevant pain levels (n = 330). Half of the included studies were rated as having a low risk of bias and the remaining were rated as having a moderate risk of bias.

CONCLUSION

Prolonged sitting increases immediate reporting of LBP in adults; however, no conclusion between sitting and clinical episodes of LBP can be made. Based upon these findings, we recommend that future prospective studies should match objectively measured sitting with temporally related pain measurements to determine whether prolonged sitting can trigger a clinical episode of LBP.