Does Using a Chair Backrest or Reducing Seated Hip Flexion Influence Trunk Muscle Activity and Discomfort? A Systematic Review

Influence of weight-bearing on the 3D movement of lumbar facet joints in the sitting position

OBJECTIVE

To analyze the motion characteristics of lumbar facet joints and to observe the effect of weight-bearing on lumbar facet joints in the sitting position.

METHODS

Ten normal subjects (5 males and 5 females) were recruited and scanned by CT, and their lumbar 3D models were reconstructed by software. The images of flexion and extension of lumbar facet joints in the sitting position were collected without weight-bearing and weight-bearing 10 kg, and the 2D model was constructed by software. The 2D-3D model was matched to restore the flexion and extension motion changes of the subjects' lumbar spine in the sitting position. Coordinates were established in the middle of the vertebral body and copied to the facet joints. Measure and record the lumbar facet joint movement distance through coordinate system. The relevant data of facet joints were collected.

RESULTS

In the L3/4 segment, after weight loading, the displacement of the left facet joint in the X axis became larger, while that in the Y axis and Z axis decreased. The displacement of the right facet joint in the X axis and Y axis increased, and the Z axis displacement decreased. The rotation angle of the bilateral facet joints also decreased. In the L4/5 segment, after loading, the displacements of the X, Y, and Z axis displacements of both sides increase, while the rotation angles of α and β increase, while the rotation angle of γ decreases. In the L5/S1 segment, the displacements of the X, Y, and Z axes on the left side decrease. The displacement of the X and Y axes on the right side decreases, while the displacement on the Z axis increases. The rotation angles of α and γ increase, and the rotation angle of the β axis decreases.

CONCLUSION

When sitting, the flexion and extension distance and rotational displacement of lumbar facet joints are not affected by weight-bearing. In addition, there is asymmetry in the movement of the left and right facet joints, and weight bearing has no effect on the asymmetry of the motion.

Prolonged slumped sitting causes neck pain and increased axioscapular muscle activity during a computer task in healthy participants - A randomized crossover study

INTRODUCTION

Sitting posture may contribute to spinal pain. Effects of postures on pain, sensitivity and muscle activity during computer tasks were investigated.

METHODS

Twenty-five healthy participants, seated at a workstation without backrest, completed four, 15-min typing tasks: A)Upright with forearm-support; B)Upright without forearm-support; C)Slumped with forearm-support; D)Slumped without forearm-support. Participants rated pain every minute on a numerical rating scale (NRS). RMS-EMG was recorded from upper/lower trapezius (UT, LT), serratus anterior and anterior/middle deltoid. At baseline and after tasks, pressure pain thresholds (PPTs) were recorded bilaterally over the head, UT, and leg.

RESULTS

All tasks caused clinically relevant increased NRS (≥2/10) compared to baseline (P < 0.001). NRS was higher in Task-D (P < 0.003) and lower in Task-B (P < 0.005) than others. PPTs did not change from baseline. Task-D caused higher UT and LT RMS-EMG (P < 0.02) than other tasks.

CONCLUSION

A 15-min task caused pain irrespective of posture with some causing larger changes than others.

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.

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.

Effectiveness of workplace active rest programme on low back pain in office workers: a stepped-wedge cluster randomised controlled trial

OBJECTIVE

This study aimed to investigate the effectiveness of workplace active rest programme (WARP) on chronic low back pain (LBP) among office workers.

DESIGN

A closed cohort, stepped-wedge cluster randomised trial was conducted. The total duration of the study was 16 weeks (4 weeks for each step). Sequence allocation was randomised, but no one was blinded.

SETTING

This study was conducted in three offices in a Japanese electronics company. One office was for the administrative department, the others are for the engineering department.

PARTICIPANTS

We recruited 29 office workers with LBP greater than 3 months. LBP due to specific injury or disease was excluded. The median age was 38 years, and 26 (90%) were male. All participants completed the study.

INTERVENTIONS

In the intervention phase, participants performed WARP comprising frequent stand-up and individualised brief exercise/physical activity during work. Physical therapists held an LBP workshop and developed tailor-made programmes before introducing WARP. We instructed participants to perform WARP at five timings during work. Control phase was set before the intervention and participants stayed as usual.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome was pain intensity of LBP assessed using the Brief Pain Inventory. The secondary outcomes were work productivity loss measured using the Work Limitations Questionnaire, LBP disability assessed using the Roland-Morris Disability Questionnaire, psychosocial subscale assessed using the STarT Back Screening Tool and physical activity measured using triaxial accelerometers. These outcomes were collected at baseline and at 4-month follow-up evaluation.

RESULTS

In the intention-to-treat analysis, WARP did not show any significant effects on pain intensity (β, 0.01; 95% CI -0.50 to 0.52) and on the secondary outcomes. The median adherence to WARP was 28.6% (IQR, 16.8-41.1), which was equal to 1.43 times per day. No adverse effect was observed.

CONCLUSIONS

The present study was unable to confirm the effectiveness of active rest in improving LBP. Hence, further study needs to investigate its effectiveness.

TRIAL REGISTRATION NUMBER

UMIN000033210.

The effects of chair intervention on lower back pain, discomfort and trunk muscle activation in office workers: a systematic review

Objectives. The chair is a standard piece of workstation equipment in an office. Previous studies showed that a suitable chair may reduce musculoskeletal symptoms. This review investigated the effect of chair intervention on lower back pain (LBP), discomfort and trunk muscle activation among office workers. Methods. Five electronic databases from 1980 to May 2020 were searched for relevant randomized and non-randomized controlled trials. The methodological quality of the included studies was assessed using the 13-item Cochrane risk of bias tool. Quality of evidence was assessed and rated according to Grading of Recommendations, Assessment, Development and Evaluations (GRADE) guidelines. Results. Two randomized controlled trials, 10 repeated-measures studies and two prospective cohort studies were included in this review. Nine studies were rated as high quality. The results indicated very low-quality to low-quality evidence for the conflicting effect of chair intervention on pain and discomfort reduction as well as trunk muscle activation among office workers. When stratified by chair type, the level of evidence for health benefits derived from any type of chair was still of very low to low quality. Conclusion. Unless supplementary high-quality studies provide different evidence, chair interventions are not recommended to reduce LBP or discomfort and activate trunk muscles.

Is active sitting on a dynamic office chair controlled by the trunk muscles?

Today’s office chairs are not known to promote active sitting or to activate the lumbar trunk muscles, both of which functions are ergonomically recommended. This study investigated a newly developed dynamic office chair with a moveable seat, specifically designed to promote trunk muscle controlled active sitting. The study aimed to determine the means by which the seat movement was controlled during active sitting. This was accomplished by quantifying trunk and thigh muscular activity and body kinematics. Additionally, the effect of increased spinal motion on muscular activity and body kinematics was analysed. Ten subjects were equipped with reflective body markers and surface electromyography on three lumbar back muscles (multifidus, iliocostalis, longissimus) and two thigh muscles (vastus lateralis and medialis). Subjects performed a reading task during static and active sitting in spontaneous and maximum ranges of motion in a simulated office laboratory setting. The temporal muscle activation pattern, average muscle activity and body segment kinematics were analysed and compared using Friedman and post-hoc Wilcoxon tests (p≤0.05). Active sitting on the new chair significantly affected the lumbar trunk muscles, with characteristic cyclic unloading/loading in response to the seat movement. Neither thigh muscle activity nor lateral body weight shift were substantially affected by active sitting. When participants increased their range of motion, the lumbar back muscles were activated for longer and relaxation times were shorter. The characteristic activity pattern of the lumbar trunk muscles was shown to be the most likely dominant factor in controlling seat movement during active sitting. Consequently, the new chair may have a potential positive impact on back health during prolonged sitting. Further studies are necessary to analyse the frequency and intensity of active sitting during daily office work.

Workplace interventions for increasing standing or walking for decreasing musculoskeletal symptoms in sedentary workers

BACKGROUND

The prevalence of musculoskeletal symptoms among sedentary workers is high. Interventions that promote occupational standing or walking have been found to reduce occupational sedentary time, but it is unclear whether these interventions ameliorate musculoskeletal symptoms in sedentary workers.

OBJECTIVES

To investigate the effectiveness of workplace interventions to increase standing or walking for decreasing musculoskeletal symptoms in sedentary workers.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, OSH UPDATE, PEDro, ClinicalTrials.gov, and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) search portal up to January 2019. We also screened reference lists of primary studies and contacted experts to identify additional studies.

SELECTION CRITERIA

We included randomised controlled trials (RCTs), cluster-randomised controlled trials (cluster-RCTs), quasi RCTs, and controlled before-and-after (CBA) studies of interventions to reduce or break up workplace sitting by encouraging standing or walking in the workplace among workers with musculoskeletal symptoms. The primary outcome was self-reported intensity or presence of musculoskeletal symptoms by body region and the impact of musculoskeletal symptoms such as pain-related disability. We considered work performance and productivity, sickness absenteeism, and adverse events such as venous disorders or perinatal complications as secondary outcomes.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened titles, abstracts, and full-text articles for study eligibility. These review authors independently extracted data and assessed risk of bias. We contacted study authors to request additional data when required. We used GRADE considerations to assess the quality of evidence provided by studies that contributed to the meta-analyses.

MAIN RESULTS

We found ten studies including three RCTs, five cluster RCTs, and two CBA studies with a total of 955 participants, all from high-income countries. Interventions targeted changes to the physical work environment such as provision of sit-stand or treadmill workstations (four studies), an activity tracker (two studies) for use in individual approaches, and multi-component interventions (five studies). We did not find any studies that specifically targeted only the organisational level components. Two studies assessed pain-related disability. Physical work environment There was no significant difference in the intensity of low back symptoms (standardised mean difference (SMD) -0.35, 95% confidence interval (CI) -0.80 to 0.10; 2 RCTs; low-quality evidence) nor in the intensity of upper back symptoms (SMD -0.48, 95% CI -.096 to 0.00; 2 RCTs; low-quality evidence) in the short term (less than six months) for interventions using sit-stand workstations compared to no intervention. No studies examined discomfort outcomes at medium (six to less than 12 months) or long term (12 months and more). No significant reduction in pain-related disability was noted when a sit-stand workstation was used compared to when no intervention was provided in the medium term (mean difference (MD) -0.4, 95% CI -2.70 to 1.90; 1 RCT; low-quality evidence). Individual approach There was no significant difference in the intensity or presence of low back symptoms (SMD -0.05, 95% CI -0.87 to 0.77; 2 RCTs; low-quality evidence), upper back symptoms (SMD -0.04, 95% CI -0.92 to 0.84; 2 RCTs; low-quality evidence), neck symptoms (SMD -0.05, 95% CI -0.68 to 0.78; 2 RCTs; low-quality evidence), shoulder symptoms (SMD -0.14, 95% CI -0.63 to 0.90; 2 RCTs; low-quality evidence), or elbow/wrist and hand symptoms (SMD -0.30, 95% CI -0.63 to 0.90; 2 RCTs; low-quality evidence) for interventions involving an activity tracker compared to an alternative intervention or no intervention in the short term. No studies provided outcomes at medium term, and only one study examined outcomes at long term. Organisational level No studies evaluated the effects of interventions solely targeted at the organisational level. Multi-component approach There was no significant difference in the proportion of participants reporting low back symptoms (risk ratio (RR) 0.93, 95% CI 0.69 to 1.27; 3 RCTs; low-quality evidence), neck symptoms (RR 1.00, 95% CI 0.76 to 1.32; 3 RCTs; low-quality evidence), shoulder symptoms (RR 0.83, 95% CI 0.12 to 5.80; 2 RCTs; very low-quality evidence), and upper back symptoms (RR 0.88, 95% CI 0.76 to 1.32; 3 RCTs; low-quality evidence) for interventions using a multi-component approach compared to no intervention in the short term. Only one RCT examined outcomes at medium term and found no significant difference in low back symptoms (MD -0.40, 95% CI -1.95 to 1.15; 1 RCT; low-quality evidence), upper back symptoms (MD -0.70, 95% CI -2.12 to 0.72; low-quality evidence), and leg symptoms (MD -0.80, 95% CI -2.49 to 0.89; low-quality evidence). There was no significant difference in the proportion of participants reporting low back symptoms (RR 0.89, 95% CI 0.57 to 1.40; 2 RCTs; low-quality evidence), neck symptoms (RR 0.67, 95% CI 0.41 to 1.08; two RCTs; low-quality evidence), and upper back symptoms (RR 0.52, 95% CI 0.08 to 3.29; 2 RCTs; low-quality evidence) for interventions using a multi-component approach compared to no intervention in the long term. There was a statistically significant reduction in pain-related disability following a multi-component intervention compared to no intervention in the medium term (MD -8.80, 95% CI -17.46 to -0.14; 1 RCT; low-quality evidence).

AUTHORS' CONCLUSIONS

Currently available limited evidence does not show that interventions to increase standing or walking in the workplace reduced musculoskeletal symptoms among sedentary workers at short-, medium-, or long-term follow up. The quality of evidence is low or very low, largely due to study design and small sample sizes. Although the results of this review are not statistically significant, some interventions targeting the physical work environment are suggestive of an intervention effect. Therefore, in the future, larger cluster-RCTs recruiting participants with baseline musculoskeletal symptoms and long-term outcomes are needed to determine whether interventions to increase standing or walking can reduce musculoskeletal symptoms among sedentary workers and can be sustained over time.

Transient perceived back pain induced by prolonged sitting in a backless office chair: are biomechanical factors involved?

It is not currently known if biomechanical factors contribute to low back pain (LBP) during prolonged sitting. Thus, this study recruited 90 participants (61 with no history of LBP, and 29 with) to sit for 1 hour where back electromyography, spine posture, and perceived pain ratings (PPR) were collected. Participants were classified as Pain Developers (PD) or Non-Pain Developers (NPD) based on their maximum PPR. PDs had significantly higher PPR (p = 0.000) and lower number of spine fidgets (p = 0.004) than NPDs. There was a significant interaction between clinical health history and pain group (p = 0.037) for PPR. Besides fidget frequency, there were no biomechanical differences between pain groups. Therefore, sitting-induced back pain does not appear to be due to posture or muscle activity; however, it may be related to micro-movement strategies. Future work should explore fidgeting further and whether healthy PDs are at risk for clinical LBP in the future. Practitioner summary: We have replicated the differential transient sitting-induced pain response observed in previous studies. Pain developers do not sit differently than non-pain developers, although they do appear to move less. More research is warranted to better understand these groups and the relationship between pain developers and future cases of back pain. Abbreviations: LBP: low back pain; PG: pain group; PD: pain developer; NPD: non-pain developer; +veHx: positive clinical history for low back pain; -veHx: negative clinical history for low back pain; RTS: right thoracic erector spinae; LTS: left thoracic erector spine; RLM: right lumbar multifidus; LLM: left lumbar multifidus; MVC: maximum voluntary contraction; Pelvic N: normalized pelvic angle; ANOVA: analysis of variance; SD: standard deviation.

An Instrumented Workstation to Evaluate Weight-Bearing Distribution in the Sitting Posture

Background

Sitting posture may be related to risk factors, including inadequate weight-bearing support, particularly when maintained for long periods. Considering that body weight is loaded in a closed support system composed of the seat, backrest, floor and working surface, the aims of the present study were to describe the development of an ergonomic sitting workstation to continuously record weight-bearing at the seat, chair, backrest, work surface, and floor and to test its measurement properties: reproducibility, criterion-related validity, and sensitivity.

Methods

Rigid bodies (1 to 30 kg) and participant weights were recorded to evaluate the workstation measurement properties.

Results

Rigid body tests showed variation values less than 0.050 kg on reproducibility test and errors below 5% of measured value on criterion validity tests. Participant tests showed no statistically significant differences between repeated measures (p ≥ 0.40), errors were less than 2% of participant weights and sensitivity presented statistically significant changes (p = 0.007).

Conclusion

The sitting workstation proposed showed to be reliable, valid and sensitive for use in future ergonomic studies to evaluate the sitting posture.

Managing low back pain in active adolescents

Adolescent low back pain has received limited research attention despite its potentially considerable impact on quality of life. The role of diagnostic triage to identify serious or specific pathology and/or order relevant investigations is considered. An overview of contemporary pain mechanisms is provided, with specific reference to the wide range of risk factors for persistent low back pain. Education and exercise framed within a biopsychosocial framework are the cornerstones of treatment. There is a lack of data on more comprehensive personalized treatment approaches among adolescents. One such approach - Cognitive Functional Therapy - which has shown promise in adults and active adolescents with low back pain, is described and illustrated using a case study. The most promising avenues, in practice and research, may be those that view adolescent low back pain as less of a local structural spinal issue and more of an indication of the general health of the adolescent.

Assessment of the ergonomic risk from saddle and conventional seats in dentistry: A systematic review and meta-analysis

Objective

This study aimed to verify whether the saddle seat provides lower ergonomic risk than conventional seats in dentistry.

Methods

This review followed the PRISMA statement and a protocol was created and registered in PROSPERO (CRD42017074918). Six electronic databases were searched as primary study sources. The "grey literature" was included to prevent selection and publication biases. The risk of bias among the studies included was assessed with the Joanna Briggs Institute Critical Appraisal Tool for Systematic Reviews. Meta-analysis was performed to estimate the effect of seat type on the ergonomic risk score in dentistry. The heterogeneity among studies was assessed using I² statistics.

Results

The search resulted in 3147 records, from which two were considered eligible for this review. Both studies were conducted with a total of 150 second-year dental students who were starting their laboratory activities using phantom heads. Saddle seats were associated with a significantly lower ergonomic risk than conventional seats [right side (mean difference = -3.18; 95% CI = -4.96, -1.40; p < 0.001) and left side (mean difference = -3.12; 95% CI = -4.56, -1.68; p < 0.001)], indicating posture improvement.

Conclusion

The two eligible studies for this review provide moderate evidence that saddle seats provided lower ergonomic risk than conventional seats in the examined population of dental students.

Active sitting with backrest support: Is it feasible?

Ergonomics science recommends office chairs that promote active sitting to reduce sitting related complaints. Since current office chairs do not fulfill this recommendation, a new chair was developed by inverting an existing dynamic chair principle. This study compares active sitting on the inverted chair during a simulated computer-based office task to two existing dynamic office chairs (n = 8). Upper body stability was analysed using Friedman ANOVA (p = .01). In addition, participants completed a questionnaire to rate their comfort and activity after half a working day. The inverted chair allowed the participants to perform a substantial range of lateral spine flexion (11.5°) with the most stable upper body posture (≤11 mm, ≤2°, p ≤ .01). The results of this study suggest that the inverted chair supports active sitting with backrest support during computer-based office work. However, according to comfort and activity ratings, results should be verified in a future field study with 24 participants. Practitioner Summary: This experimental laboratory study analyses the feasibility of active sitting with a backrest support during common office work on a new type of dynamic office chair. The results demonstrate that active sitting with a backrest support is feasible on the new but limited on existing chairs.

The effect of standing vs. variants of the seated position on lumbar intersegmental angulation and spacing: a radiographic study of 20 asymptomatic subjects

Background

Pain while sitting is the primary complaint of many patients with lumbar spinal ailments, including those with discogenic low back pain and lumbar disc herniations. There has been little basic research on the different mechanical stresses that different sitting positions place on the spine. To demonstrate the effect of different sitting positions on lumbar intersegmental relationships.

Methods

Twenty healthy male volunteer subjects were recruited. Lateral X-rays of the lower lumbar spine were taken in four positions: (I) relaxed lateral standing; (II) "standard" sitting position; (III) sitting on a "kneeling" chair; and (IV) unsupported sitting on a stool. Anterior and posterior disc height, disc space angulation, L1-S1 angulation and interspinous distance were measured.

Results

The L1-S1 lordotic angle in the standing position (48.8°±14.7°) was found to be statistically significantly greater than the angle measured with any of the sitting positions: the kneeling chair (34.0°±17.7°); hard-back chair (28.6°±14.3°); and the stool (16.6°±15.6°). Total average disc height (arithmetic sum of average disc heights L2-S1) in the lumbar spine varied with position: standing (40.5±7.75 mm); hard-back chair (38.5±6.9 mm); kneeling chair (38.4±7.9 mm); stool (36.9±7.1 mm). The mean interspinous distance over all the lumbar levels was significantly greater in each of the three seated positions than in the standing position: standing 6.8±4.5 mm; 11.6°±7.5° for the kneeling chair; 12.9±5.8 mm for the hard-back chair; 16.9±7.0 mm for the stool.

Conclusions

If segmental flexion and segmental loading are the important biomechanical correlates of pain on sitting, such patients should be most comfortable in a kneeling chair, which most closely approximates the standing position. These basic findings will allow better assessment of different seating positions from an ergonomic perspective, and hopefully lead to improvements in chair design.

Occupational interventions for the prevention of back pain: Overview of systematic reviews

INTRODUCTION

We conducted an overview of systematic reviews of interventions for the prevention of low back pain (LBP) that can be conducted in a workplace setting.

METHODS

An electronic literature search was performed in Medline, EMBASE, and the Cochrane Library. Published peer-reviewed systematic reviews and meta-analyses, which described interventions for the primary or secondary prevention of LBP applicable to a workplace setting, were eligible for inclusion. The methodological quality of the included systematic reviews was assessed with the AMSTAR tool. The primary outcome of interest was the incidence of LBP; secondary outcomes were LBP-associated absenteeism, activity interference, and costs related to LBP.

RESULTS

Twenty-eight eligible articles published between 1994 and 2016 were included in a qualitative synthesis following our screening of abstracts and full-text articles. The AMSTAR rating revealed 14 reviews of high, 10 of moderate, and 4 of low methodological quality. The identified interventions included workplace modifications (6 reviews, 10 studies, 6,751 subjects); shoe insoles (4 reviews, 6 studies, 2,356 subjects); and lumbar supports and other assistive devices (15 reviews, 18 studies, 60,678 subjects). Educational interventions investigated were back schools (10 reviews, 30 studies, 9,973 subjects); manual material handling techniques/advice (6 reviews, 24 studies, 10,505 subjects); and other forms of instruction including pamphlets, booklets, and other media (four reviews, 14 studies, 11,991 subjects). Exercise interventions, investigated in 12 reviews (35 studies, 19,330 subjects), showed moderate quality evidence of effectiveness for exercise interventions alone or in conjunction with educational interventions; no other type of intervention was consistently effective in the prevention of LBP or LBP-associated outcomes of interest.

CONCLUSIONS

Our overview provides evidence of effectiveness for exercise with or without educational interventions in the prevention of LBP.

PRACTICAL APPLICATIONS

Exercise interventions with or without educational interventions that can be applied in the workplace have the potential to prevent LBP.

Comparison of chairs based on HDsEMG of back muscles, biomechanical and comfort indices, for violin and viola players: A short-term study

This work investigates the effect of different seats on violin and viola players sitting postures using High-Density-surface-Electromyography techniques (HDsEMG), biomechanical and comfort indices. Five types of chairs were assessed on 18 violin and three viola players by comparing: (a) pelvic tilt and kyphosis and lordosis angles, (b) subjective comfort indices, and (c) EMG amplitude of erector spinae and trapezius. Sitting "as you like" on a standard orchestra chair is the condition with the highest subjective comfort (but not significantly different from other chairs). A saddle chair with low back support is associated to the lowest EMG of the erector spinae (p < 0.05) and a saddle stool is associated to the spinal angles closest to those of the standing posture. In 12 out of 21 (57%) musicians, the erector spinae was activated in an intermittent manner, regardless of the chair used. These findings justify further research on the selected chairs, on muscle fatigue and on the intermittent postural control strategy.

The effect of a dynamic chair on seated energy expenditure

Dynamic sitting approaches have been advocated to increase seated energy expenditure with the view of lessening the sedentary nature of the task. This study compared energy expenditure (EE) and overall body discomfort on a novel dynamic chair with a standard office chair. Fifteen pain-free participants completed a DVD viewing task on both chairs in a randomised order. Energy expenditure and discomfort were collected simultaneously. Linear mixed models were used to analyse steady-state EE recorded on each of the chairs. Differences in discomfort were analysed using Wilkoxon Signed Rank Tests. Sitting on the novel dynamic chair significantly (p = 0.005) increased energy expenditure compared to a standard office chair. The discomfort experienced was mild overall, but was significantly greater on the dynamic chair (p = 0.004). Whilst the EE was seen to be significantly higher on the dynamic chair, the MET values are still below 1.5 METS. Thus, the use of a dynamic chair does not seem to be the most effective measure to prevent sedentary behaviour. Practitioner Summary: Sitting on a dynamic chair increased energy expenditure compared to sitting on a standard office chair among pain-free participants. Whilst the EE was seen to be significantly higher on the dynamic chair, the MET values are still below 1.5 METS (low level EE).

Effectiveness of additional trunk exercises on gait performance: study protocol for a randomized controlled trial

BACKGROUND

Evidence is lacking concerning the effect of additional trunk rehabilitation on gait performance. Investigating gait performance by both clinical and biomechanical outcome measures might lead to new scientific insights into the importance of the trunk during gait rehabilitation in people suffering from stroke. This protocol was written according to the SPIRIT 2013 Statement.

METHODS AND DESIGN

An assessor-blinded randomized controlled trial will be conducted in patients with impaired trunk control after stroke. A total of 60 patients will be randomly allocated to the control or the experimental group by means of sealed opaque envelopes. They will receive either 16 h of additional trunk exercises (experimental group) or cognitive exercises (controls) for 1 h a day, 4 days a week for 4 weeks. Patients will also receive 2 h of standard care consisting of physiotherapy and occupational therapy. Gait performance will be assessed clinically by the Tinetti Test and biomechanically by means of a full body gait analysis. In addition, the effect of the exercise protocol on the trunk itself and trunk activities of daily living will be assessed by the Trunk Impairment Scale and the Barthel Index.

DISCUSSION

Despite the evidence demonstrating the importance of trunk control after stroke, studies about the effects of trunk rehabilitation on gait performance are inconsistent. In the current study, a more sophisticated treatment protocol will be used to enlarge therapeutic improvements, the relationship between clinical and biomechanical measures of gait performance can be investigated, and the sustainability of the effects of trunk exercises over time will be examined. Since clinical improvements are of greater importance to patients and physiotherapists, clinical assessment scales will be used as primary outcome measures.

TRIAL REGISTRATION

ClinicalTrials.gov, ID: NCT02708888 . Registered on 2 March 2016.