Low back pain scores correlate with the cytokine mRNA level in lumbar disc biopsies: a study of inflammatory markers in patients undergoing lumbar spinal fusion.

PURPOSE: The molecular mechanism behind pain in degenerative disc disease (DDD) and chronic low back pain (LBP) patients is largely unknown. This present study examines the association of LBP and disability to mediators of the inflammatory cascade, as indexed by mRNA gene expression of pro-inflammatory cytokine markers in the intervertebral disc (IVD). METHODS: Biopsies of the annulus fibrosus (AF) and the nucleus pulposes (NP) from patients with DDD undergoing 1-2 level fusion surgery at L4/L5 or L5/S1 were obtained from total of 34 patients [9 M, 25 F] with average age of 53 [32-63]. The mRNA expression of TNF-α, IL-1ß, and IL-6 in the AF and NP was analyzed using quantitative real-time polymerase chain reaction (RT-qPCR), and the expression level of these markers was correlated to the visual analogue scale (VAS) and Oswestry Disability Index (ODI) scores (0-100) for pain and disability. RESULTS: We report a statistically significant positive correlation between pain intensity (VAS score) and the expression of TNF-α in both the AF (r = 0.54, p = 0.001) and NP (r = 0.40, p = 0.02), similarly with IL-1ß in AF (r = 0.37, p = 0.02) and IL-6 in NP (r = 0.40, p = 0.02). In addition, we found significant positive correlation observed between disability score (ODI) and expression of IL-6 in both AF (r = 0.36, p = 0.03) and NP (r = 0.41, p = 0.01). CONCLUSION: We conclude that the intensity of LBP and disability is associated with the level of inflammation in the disc.

The reproducibility of quantitative measurements in lumbar magnetic resonance imaging of children from the general population.

STUDY DESIGN: Quantitative lumbar magnetic resonance imaging (MRI) measurements in children were taken twice and analyzed for intra- and intertester reproducibility. OBJECTIVE: To evaluate the reproducibility of a variety of lumbar quantitative measurements taken from MRIs of children from the general population. SUMMARY OF BACKGROUND DATA: The reproducibility of lumbar quantitative measurements has never been tested on MRIs of children from the general population. This is a prerequisite for a reliable anatomic characterization of the immature spine in normal and pathologic conditions. METHODS: Lumbar quantitative measurements from 40 T2-weighted lumbar (L1-S1) MRIs of children from the general population were taken twice by 1 tester for intratester reproducibility and compared with the same measurements (L4-S1) of the same MRIs taken by a second tester for intertester reproducibility. The following parameters were measured using the iQ-VIEW system (IMAGE Information Systems Ltd., version 1.2.2, Plauen, Germany): Linear measurements--zygoappophyseal facets and interfacet widths, and vertebral body (VB), pedicle and intervertebral discs heights, widths, and lengths. Angular measurements--zygoappophyseal tranverse superior facet angles, sagittal VB, and disc wedging, lumbar lordosis, and sacral inclination. Statistical analysis included the concordance correlation coefficient (CCC), and Bland and Altman's limits of agreement (LOA). RESULTS: A total of 6160 measurements were analyzed. Good to excellent intratester reproducibility (0.75 < or =CCC < or =0.99) was indicated for all linear measurements (except for pedicle heights) (LOA: -4.76; 5.74 mm) and for angular measurements related to the facets orientation, lumbar lordosis, and sacral inclination (LOA: 11.22 degrees ; 12.34 degrees). VB and disc sagittal wedging manifested poor intratester reproducibility (CCC < 0.75). Good to excellent intertester reproducibility was indicated for 70% of all linear measurements (LOA: -5.83; 4.59 mm) and for all angular measurements in the lumbar spine (L4-S1) (LOA: -9.96 degrees ; 14.62 degrees) except for VB and disc sagittal wedging at L5 (CCC < 0.75). CONCLUSION: Quantitative lumbar MRI measurements in children from the general population were found to be reproducible indicating a good visualization of immature vertebral anatomic margins on MRIs and an accurate definition of the measurement protocol.

Clinical assessment of prognostic factors for long-term pain and handicap after whiplash injury: a 1-year prospective study.

BACKGROUND AND PURPOSE: Physical mechanisms are the possible factors involved in the development and maintenance of long-term handicaps after acute whiplash injury. This study prospectively examined the role of active neck mobility, cervical and extra-cervical pains, as well as non-painful complaints after a whiplash injury as predictors for subsequent handicap. METHODS: Consecutive acute whiplash patients (n = 688) were interviewed and examined by a study nurse after the median of 5 days after injury, and divided into a high- or a low-risk group by an algorithm based on pain intensity, number of non-painful complaints and active neck mobility [active cervical range of motion (CROM)]. All 458 high-risk patients and 230 low-risk patients received mailed questionnaires after 3, 6 and 12 months. Two examiners examined all high-risk patients (n = 458) and 41 consecutive low-risk patients at median 11, 109, 380 days after injury. The main outcome measures were: handicaps, severe headaches, neck pain and neck disability. RESULTS: The relative risk for a 1-year disability increased by 3.5 with initial intense neck pain and headaches, by 4.6 times with reduced CROM and by four times with multiple non-painful complaints. CONCLUSION: Reduced active neck mobility, immediate intense neck pain and headaches and the presence of multiple non-painful complaints are the important prognostic factors for a 1-year handicap after acute whiplash.

Modic changes, possible causes and relation to low back pain.

UNLABELLED: In patients with low back pain (LBP) it is only possible to diagnose a small proportion, (approximately 20%), on a patho-anatomical basis. Therefore, the identification of relevant LBP subgroups, preferably on a patho-anatomical basis, is strongly needed. Signal changes on MRI in the vertebral body marrow adjacent to the end plates also known as Modic changes (MC) are common in patients with LBP (18-58%) and is strongly associated with LBP. In asymptomatic persons the prevalence is 12-13%. MC are divided into three different types. Type 1 consists of fibro vascular tissue, type 2 is yellow fat, and type 3 is sclerotic bone. The temporal evolution of MC is uncertain, but the time span is years. Subchondral bone marrow signal changes associated with pain can be observed in different specific infectious, degenerative and immunological diseases such as osseous infections, osteoarthritis, ankylosing spondylitis and spondylarthritis. In the vertebrae, MC is seen in relation to vertebral fractures, spondylodiscitis, disc herniation, severe disc degeneration, injections with chymopapain, and acute Schmorl's impressions. The aim of this paper is to propose two possible pathogenetic mechanisms causing Modic changes. These are: A mechanical cause: Degeneration of the disc causes loss of soft nuclear material, reduced disc height and hydrostatic pressure, which increases the shear forces on the endplates and micro fractures may occur. The observed MC could represent oedema secondary to the fracture and subsequent inflammation, or a result of an inflammatory process from a toxic stimulus from the nucleus pulposus that seeps through the fractures. A bacterial cause: Following a tear in the outer fibres of the annulus e.g. disc herniation, new capilarisation and inflammation develop around the extruded nuclear material. Through this tissue it is possible for anaerobic bacteria to enter the anaerobic disc and in this environment cause a slowly developing low virulent infection. The MC could be the visible signs of the inflammation and oedema surrounding this infection, because the anaerobic bacteria cannot thrive in the highly aerobic environment of the MC type 1. PERSPECTIVES: One or both of the described mechanisms can - if proven - be of significant importance for this specific subgroup of patients with LBP. Hence, it would be possible to give a more precise and relevant diagnosis to 20-50% of patients with LBP and enable in the development of efficient treatments which might be antibiotics, special rehabilitation programmes, rest, stabilizing exercise, or surgical fixation, depending on the underlying cause for the MC.

Are smooth pursuit eye movements altered in chronic whiplash-associated disorders? A cross-sectional study.

OBJECTIVE: To evaluate whether smooth pursuit eye movements differed between patients with long-lasting whiplash-associated disorders and controls when using a purely computerized method for the eye movement analysis. DESIGN: Cross-sectional study comparing patients with whiplash-associated disorders and controls who had not been exposed to head or neck trauma and had no notable neck complaints. METHODS: Smooth pursuit eye movements were registered while the subjects were seated with and without rotated cervical spine. SUBJECTS: Thirty-four patients with whiplash-associated disorders with symptoms more than six months after a car collision and 60 controls. RESULTS: Smooth pursuit eye movements were almost identical in patients with chronic whiplash-associated disorders and controls, both when the neck was rotated and in the neutral position. CONCLUSION: Disturbed smooth pursuit eye movements do not appear to be a distinct feature in patients with chronic whiplash-associated disorders. This is in contrast to results of previous studies and may be due to the fact that analyses were performed in a computerized and objective manner. Other possible reasons for the discrepancy to previous studies are discussed.

Nonorganic pain drawings are associated with low psychological scores on the preoperative SF-36 questionnaire in patients with chronic low back pain.

The Short Form 36 questionnaire (SF-36) measures general health and well-being. Within the last 5 years it has been used increasingly to characterise patients in the medical literature. Relatively few studies have used the SF-36 on patients with chronic low back pain undergoing preoperative evaluation, but results suggest that it may be predictive of surgical outcome. Pain drawings are a routine part of evaluation prior to spinal surgery in several centres, since their classification of organic or nonorganic has been shown in some studies to correlate well with psychological characteristics predicting poor outcome. The purpose of the present study was to assess possible correlations between nonorganic pain drawings and the psychological scales in the SF-36. We included 128 patients in the study, all of them referred from other hospitals. Previous spinal surgery had been undergone by 25%, and 59% required daily medication because of low back pain. All patients completed pain drawings using predefined symbols These pain drawings were scored dichotomously as organic or nonorganic based on a brief description of a typical nonorganic characteristics. Patients also completed the Danish version of the SF-36 questionnaire. Statistical analysis was performed using logistic regression analysis. The pain drawing classification was used as the dependent variable and scores on the eight scales of the SF-36 as independent variables. P values of <0.05 were considered significant. The mean scores of the patient population on all eight scales were significantly lower than Danish norms. The only scales that correlated with the presence of nonorganic pain drawings were emotional role (RE) and mental health (MH), both measuring psychological health. The odds ratio (OR) of receiving a nonorganic pain drawing was 22 (95% confidence interval, or CI, 7-65) if the scores on RE and MH were more than 2 standard deviations (SD) below the Danish norm. This is the first study providing evidence that pain drawing ratings are influenced by the psychological scales of the SF-36. The clinical relevance of this observation regarding prediction of outcome after spinal surgery should be assessed in future studies.

Functional restoration versus outpatient physical training in chronic low back pain: a randomized comparative study.

STUDY DESIGN: A randomized parallel-group comparative trial with a 1-year follow-up period was performed. OBJECTIVE: To compare the effect of a comprehensive functional restoration program involving intensive physical training, ergonomic training, and behavioral support (39 hours per week for 3 weeks) with the effect of outpatient intensive physical training (1.5 hours three times per week for 8 weeks). SUMMARY OF BACKGROUND DATA: Nonrandomized studies conducted in the United States favor functional restoration for patients with chronic low back pain. Two previously reported randomized studies from the authors' Back Center in Copenhagen concur with this recommendation, although the positive effects in one of the studies had faded out after 2 years. Randomized functional restoration studies in Canada and Finland have failed to demonstrate any substantive effect. METHODS: Initially, 138 patients with chronic low back pain were included in the current study. They then were randomized to either functional restoration (n = 64) or outpatient intensive physical training (n = 74). Of the initial 138 patients, 11 never started (5 and 6, respectively); 21 dropped out during treatment (8 and 13); and 7 of the graduates did not take part in the 1-year follow-up evaluation (3 and 4). The conclusions were drawn from the 99 patients (48 and 51, respectively) who graduated and participated in a 1-year follow-up evaluation. The median age of the patients was 42 years (range, 21-55 years) The female-to-male ratio was 68 to 31, and the median sick leave days during the preceding 3 years was 180 (range, 0-1080 days). The average back pain was rated 5.5 on a scale of 0 (no pain) to 10 (maximal pain). For these variables, there were no important differences between the groups. However, the functional restoration group tended to be more capable of work at baseline (58% vs 42%; P = 0.09). RESULTS: At the 1-year follow-up evaluation, overall assessment favored functional restoration. Otherwise, no significant differences were observed regarding work capability, sick leave for those at work, health care contacts,back pain, leg pain, or self-reported activities of daily living. CONCLUSIONS: Only in terms of overall assessment, the functional restoration program was superior to a comparatively short time-consuming outpatient physical training program. DISCUSSION: It may be that lower economic benefits during sick leave in the United States lead to favorable results from functional restoration programs, whereas greater benefits in Canada, Finland, and Denmark result in different conclusions. Finally, it may be that the difference in results across studies points simply to whether the studies were randomized.

The "Hawthorne effect"--what did the original Hawthorne studies actually show?

The "Hawthorne effect" is often mentioned as a possible explanation for positive results in intervention studies. It is used to cover many phenomena, not only unwitting confounding of variables under study by the study itself, but also behavioral change due to an awareness of being observed, active compliance with the supposed wishes of researchers because of special attention received, or positive response to the stimulus being introduced. At times, the term seems to be used as a social equivalent to "placebo effect". In social research, there is much critical literature indicating that, in general, the term "Hawthorne effect" should be avoided. Instead of referring to the ambiguous and disputable Hawthorne effect when evaluating intervention effectiveness, researchers should introduce specific psychological and social variables that may have affected the outcome under study but were not monitored during the project, along with the possible effect on the observed results.

[Predictive factors of the effect of multidisciplinary, intensive rehabilitation of back pain. Demographic, socioeconomic and physical factors]. / Praediktive faktorer for effekt ved tvaerfaglig, intensiv rygrehabilitering. Demografiske, socioøkonomiske og fysiske faktorer.

In order to identify possible predictive factors for success from rehabilitation in a functional restoration (FR) program for patients with chronic low back pain, pre-treatment baseline variables were correlated to different outcome parameters following treatment in either a FR program or control programs. A prospective clinical trial involving 816 patients was carried out. Of the total cohort 621 patients participated in a FR program and 195 in control groups. The results showed that different factors could be identified as useful in predicting outcome from a FR program, but most of these factors were also shown to predict success for controls of shorter outpatient programs or of no treatment.

[Back pain--from the viewpoint of medical technology. Danish National Board of Health]. / Ondt i ryggen--set i et MTV-perspektiv.

The appearance of various consensus reports, guidelines, Cochrane Centers, and other evidence-based medicine initiatives during the past decade has resulted in marked improvement in the rational utilisation of available knowledge of attitudes toward the issue of low back pain (LBP). Moreover, owing to the ready access to updated data bases, this knowledge has been disseminated with incredible speed. In the spring of 1995, the Danish National Board of Health in Denmark convinced a multidisciplinary team of back specialists to tailor data available in the international reports for Danish needs. The article outlines the findings of this team, the major recommendations being that providing information is preferable to treatment, that patients should be encouraged to remain active, that physical exercise should be kept up except during the acute phases, that most episodes of LBP are to be considered life events rather than automatic reasons to seek treatment, and that passive treatment should be minimised, though manipulation may be helpful in the short term.

Can it be predicted which patients with chronic low back pain should be offered tertiary rehabilitation in a functional restoration program? A search for demographic, socioeconomic, and physical predictors.

STUDY DESIGN: A prospective clinical trial was conducted that involved six groups of patients with chronic low back pain selected from a large cohort (N = 816). OBJECTIVES: To correlate pretreatment baseline variables with outcome parameters after treatment in a functional restoration program or in control programs, to identify possible factors predictive of the need for functional restoration. SUMMARY OF BACKGROUND DATA: Since the functional restoration program was first described, research has focused on identifying patients who will or will not benefit from such a program. The value of previous studies is limited, however, because predictive factors from a control group were not "subtracted." METHODS: Eight hundred sixteen patients with chronic low back disability were included. All had a structured medical examination, including various physical tests before participation in either a functional restoration program (n = 621) or shorter "control" outpatient programs (n = 144). A smaller group of the cohort (n = 51) had no treatment and served as a pure control group. Six groups were selected from the cohort: Three underwent an identical functional restoration program and three underwent different outpatient control programs. Several baseline demographic, physical, and socioeconomic variables were correlated to 1-year outcome parameters. RESULTS: Age, days of sick leave, connection to the work force, and back pain intensity, were significantly correlated to success 1 year after entry into the study in all groups, no matter what kind of treatment was administered. Back muscle endurance, sports activity, activity of daily living scores, and vibrations were of importance in some outcome parameters for success after functional restoration. Smoking was positively correlated to disability pension. Days of sick leave and, in functional restoration, ability to work were the only factors that were correlative with statistics for people who withdrew. CONCLUSIONS: Different factors can be identified as predictive of outcome in a functional restoration program, but most of these factors were also shown to predict success for shorter control outpatient programs or of no treatment.

A prospective, randomized 5-year follow-up study of functional restoration in chronic low back pain patients.

A functional restoration (FR) program, dealing with a combination of intensive physical and ergonomic training, psychological pain management, and patient education, was tested in two randomized, parallel group studies. In one of these patients following the FR program were compared with a non-treated control group (project A), and in the other with patients on two less intensive treatment programs (project B). A total of 238 chronic low back pain patients participated in the two studies, 106 entering project A and 132 project B. Patients from the two projects were comparable except that the patients in project A were recruited from all over the country, whereas patients in project B all were living in and around Copenhagen. Thirteen patients never started any treatment, and 20 patients (9%) dropped out during the treatment period. Of the 207 who completed treatment, 89% returned a mailed questionnaire 5 years later. This was the case for 55% of the drop-outs. The questions referred to work situation, pain level, activities of daily living, days of sick leave, contact with health care professionals, physical activity, use of medication, and a subjective overall assessment. The results show that in project A the treated group reported significantly fewer contacts with the health care system and significantly fewer days of sick leave over the 5-year follow-up period compared to the control group. In all other parameters, including work ability, there was no statistically significant difference between the two groups. In project B, patients treated in the FR program did significantly better in most measured parameters, except in leg pain, use of pain medication and sport activity, where no significant differences were found between groups. The overall result shows a positive long-term effect of the FR program, but it also shows the necessity of testing a given treatment in different projects and designs, among other things due to statistical variations.

Functional restoration for chronic low back pain. Two-year follow-up of two randomized clinical trials.

STUDY DESIGN: Two randomized, prospective clinical trials involving 238 chronic low back disability patients were carried out. Results at 2-year follow-up are presented. OBJECTIVES: To compare the clinical outcomes of a multidisciplinary functional restoration program with a nontreated control group (Project A) and with two less intensive but different training programs (Project B). SUMMARY OF BACKGROUND DATA: The effectiveness of functional restoration programs has not been firmly established. Results from trials carried out in the United States differ from those in trials conducted in other countries. Only a few of these studies have been carried out as prospective and randomized clinical studies. METHODS: Two hundred thirty-eight patients with chronic low back disability of at least 6 months' duration were included. There were 106 patients in project A and 132 patients in project B. Two years after completion of treatment patients were mailed a questionnaire that included questions regarding their work status, pain and disability levels, number of sick leave days, number of medical care contacts, medication use, physical activity levels, and subjective overall assessment of their "back life situation." RESULTS: Patients in both studies were comparable at inclusion, except that patients in Project A were recruited from all of Denmark, whereas those in Project B were from the greater Copenhagen area. Thirteen patients did not report for treatment after randomization. Of the remaining 225 patients, 20 (9%) did not complete treatment. The questionnaire response rate was 94%. In Project A, those patients receiving treatment (functional restoration) reported significantly less contact with the health care system, fewer sick leave days, and a less disabled life style during the follow-up period, compared with reports of patients in the control group. Other effect parameters did not demonstrate a significant difference between the two groups. In Project B, all effect parameters reported, except leg pain and medication usage, were significantly in favor of functional restoration, compared with reports from the less intensively treated groups. CONCLUSIONS: The functional restoration program seems effective in various parameters compared with the less intensive programs, but the differences in outcome in the two parallel studies indicate the necessity of testing a treatment program in different settings, in that the statistical variation may be a major factor in results of different studies.

Intensive training, physiotherapy, or manipulation for patients with chronic neck pain. A prospective, single-blinded, randomized clinical trial.

STUDY DESIGN: A randomized, prospective clinical study was conducted that included 119 patients with chronic neck pain of greater than 3 months' duration. OBJECTIVES: To compare the relative effectiveness of intensive training of the cervical musculature, a physiotherapy treatment regimen, and chiropractic treatment on this patient group. SUMMARY OF BACKGROUND DATA: There are only a few studies involving chronic neck pain patients representative of those seeking care in primary health care centers. Mobilization techniques and intensive training have been shown to be useful, but cervical manipulation has not been assessed. Clinical results involving these commonly used therapies have not been compared. METHODS: A total of 167 consecutive patients were screened. One hundred nineteen patients were admitted to the study and were randomized according to Taves' minimization principles. Primary outcome measures included self-reported pain, disability, medication use, patients' perceived effect, and physician's global assessment. Patients were assessed at enrollment and at completion of the study. Postal questionnaires were used to carry out 4- and 12-month follow-up assessments. Secondary outcome measures included active range of motion of the cervical spine as well as strength and endurance measurements of the cervical musculature. These measurements were carried out at enrollment and completion of the study. RESULTS: A total of 88% of the patients completed the study. Of these, 97% completed the 4-month questionnaire and 93% the 12-month questionnaire. Patients from all three groups demonstrated significant improvements regarding self-reported pain and disability on completion of the study. Improvements were maintained throughout the follow-up period. Medication use was also significantly reduced in all groups. There was, however, no significant difference between groups at any assessment period. Physician's and patients' assessments were also positive, and again group scores were essentially equal. Patients who underwent intensive training demonstrated significantly greater endurance levels at the completion of treatment. CONCLUSIONS: There was no clinical difference between the three treatments. All three treatment interventions demonstrated meaningful improvement in all primary effect parameters. Improvements were maintained at 4- and 12-month follow-up. However, whether this was a result of the treatments or simply a result of time is unknown. Future studies will be necessary to delineate ideal treatment strategies.

Comparison of three intensive programs for chronic low back pain patients: a prospective, randomized, observer-blinded study with one-year follow-up.

In a randomized, blinded study, we compared the outcome from a full-time functional restoration program with the outcome from shorter active rehabilitation programs for patients with chronic, disabling low back pain. The study initially included 132 patients, randomized into one of three treatment programs: (1) an intensive 3-week multidisciplinary program; (2) active physical training and back school; or (3) psychological pain management and active physical training. Nine of the randomized patients never started in any program, so the studied population consisted of 123 patients. Of these, 14 patients (11%) dropped out. The results presented here are at 1 year following treatment, where we achieved a 92% response rate, including the drop-outs. The functional restoration program was superior to the shorter programs as to work-ready rate, health care contacts, back pain level, disability level, staying physically active, and reduction in analgesics. There was no significant difference between Programs 2 and 3 in most of these parameters. As for sick leave and leg pain, there was no significant difference between Programs 1 and 2, although a difference was observed when comparing Program 3 with each of the other two. Conclusively, it seems that there is human, as well as economical, benefit from a functional restoration program compared to less intensive programs for these patients.

Functional restoration in chronic low back pain.

Conventional treatments have not slowed down the ever expanding low back pain (LBP) problem. Traditional treatment has most probably contributed to the growth of the problem. Therefore, in a search for new solutions, 'functional restoration' has been devised. In connection with chronic LBP the term has been associated with a full-day program lasting from 3 to 5 weeks. It includes multidisciplinary treatment of patients in groups with intensive physical and ergonomic training, psychological pain management, back school, as well as teaching in social/work related issues. The key concepts are 'acceptance of the pain', 'activity', 'self-responsibility', 'multidisciplinary' and 'quantitative functional evaluation (QFE)'. The latter is aimed so that the participants can feel the physical improvement, encouraging them to be able to go back to work, or at least to lead a more active life style. Several controlled studies suggest a lasting effect in terms of regaining their ability to work and improving pain behavior for a good part of disabled chronic LBP patients. However, it is noteworthy that randomized studies seemingly show poorer results than studies not employing randomized controls.

What does a backrest actually do to the lumbar spine?

It is generally believed that a backrest facilitates lumbar lordosis. To test this, the spontaneously adopted postures of 12 healthy subjects were measured by a statometric method during 2-h sitting periods on three types of chairs in a stratified sequence. The only difference between the three workstations regarded backrest: 'A' had no backrest; 'B' had a vertical lumbar backrest; and 'C' had an anteriorly curved backrest. In general, the most lordotic postures were assumed with backrest C, whereas backrest B rather facilitated kyphosis as compared with sitting without a backrest. However, when specifically considering passive sitting, i.e. reading, both types of backrest facilitated kyphosis. Moreover, spinal shrinkage was evaluated by measuring exact height before and after each 2-h sitting period. This was done to assess spinal load. From this perspective, backrest C induced the greatest load on the spine. In conclusion, the traditional conception that a backrest facilitates lordosis is apparently not true. It seems rather that backrests actually facilitate the opportunity for the user to stabilize their lumbar spines by providing their lower backs with support, resulting in relative kyphotic increases. The practical ergonomic applications from this study are unclear. However, traditional concepts in backrest ergonomy should be re-considered.