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The effect of an acupressure backrest on pain and disability in office workers with chronic low back pain: A randomized, controlled study and patients’ preferences
Complementary Therapies in Medicine (2015) 23, 347—355
Available online at www.sciencedirect.com
ScienceDirect journal homepage: www.elsevierhealth.com/journals/ctim
The effect of an acupressure backrest on pain and disability in office workers with chronic low back pain: A randomized, controlled study and patients’ preferences Nithima Purepong ∗, Sirinant Channak, Sujitra Boonyong, Premtip Thaveeratitham, Prawit Janwantanakul Department of Physical Therapy, Faculty of Allied Health Sciences, Chulalongkorn University, Bangkok, Thailand Available online 18 March 2015
KEYWORDS Low back pain; Backrest; Acupressure
Summary Objective: This study investigated the effects of an acupoint-stimulating lumbar backrest on pain and disability in office workers who suffering from low back pain (LBP) as well as the preference influence on pain and disability. Methods: Sixty-four participants were randomly assigned to two groups: one with no intervention (n = 32) and another with 1 month of backrest use (n = 32). An additional group (n = 37) who wished to try 1 month of acupressure backrest were recruited to indicate the preference effect. Pain and disability were two key outcomes. Results: Significant differences between control and randomized acupressure backrest groups were found at 2 week period for disability and at 4 weeks for pain after the backrest use. Also, significant differences were found in both groups for 3 month period with an increase of the treatment effect on pain and disability. Both control and randomized acupressure backrest groups showed greater improvement in pain and disability scores which were more than the minimal clinically important change (30% improvement for both outcomes). No significant difference was found for pain and disability between the randomized and preferred backrest groups. Conclusion: These findings suggested 1-month of acupressure backrest use could improve LBP conditions. Preference was not a powerful moderator to the significant treatment effect. © 2015 Elsevier Ltd. All rights reserved.
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Corresponding author. Tel.: +66 2 218 3767; fax: +66 2 218 3766. E-mail addresses: [email protected] (N. Purepong), [email protected] (S. Channak), [email protected] (S. Boonyong), [email protected] (P. Thaveeratitham), [email protected] (P. Janwantanakul). http://dx.doi.org/10.1016/j.ctim.2015.03.005 0965-2299/© 2015 Elsevier Ltd. All rights reserved.
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Introduction Low back pain (LBP) is the most common musculoskeletal disorder. Incidences of LBP are growing and creating an economic burden for society.1 The total costs of LBP in the United States exceed $100 billion per year.2 In Thailand, the reported cost of management for low back pain in Thailand was about $72.59 USD per person in one year.3 Thirty-four percent of 1428 Bangkok office workers surveyed were found to experience low back pain during a period of 12 months, which they attributed to work.4 Office workers who mostly spent prolonged periods of work seated regarded their chairs as crucial workstation equipment. Several aspects of chair design were mentioned in healthy and safety guidelines for computer ergonomics.5,6 One of the important factors for workers seated for prolonged periods is reduction of load through the lumbar spine. The reduced load could be achieved by transferring body weight through the armrests and feet as well as through the backrest.7 Backrests have become the focal point of several studies.8—10 Several designs of backrests have been proposed.11—13 The guidelines for office ergonomics recommended that a backrest should support the lumbar spine6 with have a specific size without restricting movement of the spine or upper extremity.14 Many studies were conducted to explore the effects of backrests with lumbar support while seated among normal subjects,10,11,15 but few clinical research studies involving LBP were conducted.15,16 Some of them indicated positive effects of backrests with lumbar support for LBP15 however, the treatment effect of backrests was still inconclusive. Therefore it was important and necessary to further develop the backrest and investigate its curative effects for LBP among office workers who sit for protracted periods. Acupressure, a complementary and alternative therapy, has received increasing attention for its manipulated method, which uses fingers instead of needles on the acupoints. The mechanism of pain relief under the acupressure effect is caused by increasing threshold pressure, circulating blood and reducing waste products such as substance P and histamine.17 In addition, the gate control theory of Wall and Melzack18 could explain the pain theory and the endorphin release.19 The effect of acupressure for LBP has been demonstrated by a randomized, controlled trial.20,21 Based on the knowledge of traditional Chinese medicine and the recommended use of backrests with lumbar support among office workers, a backrest with adjustable acupressure lumbar support was designed and developed for LBP-suffering office workers. The aim of this study was to investigate the effectiveness of the acupressure backrest applied for a 1-month period among office workers with chronic LBP. The randomized controlled trials are considered as the most robust method.22 However, the weakness of randomization was that the patient with low preference to intervention may participate partially or refuse the study protocol.23 Otherwise, the Preference Collaborative Review Group23 had reported that the preferences among patients in musculoskeletal trials were associated with their treatment effects. For this reason, we integrated both designs in this study in order to investigate the effect of an adjustable acupressure
N. Purepong et al. backrest on pain and disability as well as the preference effect of the acupressure backrest. Participants who preferred using the backrest were recruited to participate in this study in order to control the preference effects.
Methodology Study design A randomized, controlled study design comparing the control and acupressure backrest groups was conducted for the study. Participants who agreed to randomization were assigned to either a control group or an acupressure backrest group using the computers generating random numbers. Participants who declined to be allocated to the randomized groups were assigned to the preferred acupressure backrest group.
Participants Participants consisted of office workers who worked in government offices or public enterprise in Bangkok, Thailand. The participants were aged 20—60 years, diagnosed as having chronic non-specific LBP (≥3 months), worked in their current position for at least 1 year, sat for at least 2 h per working period, and were able to write and read Thai. Standard office chairs were used, which consisted of specific components as per recommendations from the Ministry of Labor offices, Canada6 and Chaffin et al.24 Participants were excluded if they had a BMI of >25 kg/m2 , history of nonemployment related LBP, indication of neurological deficit, traumatic spinal fracture, serious spinal diseases such as cancer or tumors, previous spinal surgery, or were pregnant. Also excluded were those who experienced bleeding from the back, or had open wounds, contusions or swelling.
Sample size Estimates of variability for the two key outcomes (pain and disability) were obtained from a pilot study and power calculation (˛ = 0.05; (1 − ˇ) = 0.90; effect size = 0.84). Based on this, 27 participants were required for each group. Allowing for 15 percent attrition by 3-month follow-up, a sample size of 32 participants per randomized group was required for this study.
Intervention The study was approved by the Chulalongkorn University Human Ethics Committee. Written consent was obtained from all participants. Participants were asked to fill out the baseline data which consisted of three self-administered questionnaires. They were requested to continue normal activities and to avoid other forms of treatment while receiving intervention. However, if participants requested another form of treatment, it was recorded by a physical therapist.
The effect of an acupressure backrest on pain and disability in office workers with chronic low back pain
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Figure 1 The acupressure backrest was composed of lumbar support with the wooden acupressure-point stimulation device (A) at the center, belt (B) and lock (C) to fix the backrest to the office chair.
Control group No intervention was provided to the control group; however, they were able to contact the physical therapist who provided the treatment if they needed advice concerning back pain for the period of one month. The physical therapist would provide standard advice and recommend appropriate posture for sitting at a work station.
Acupressure backrest group The acupressure backrest was installed onto the office chairs of participants in both the allocated and backrest groups by the same physical therapist. The physical therapist explained how to effectively sit on the office chair with the backrest. The physical therapist visited their work stations twice a week in order to check the level of the acupressure point device and position of the backrest. Also, three short message signals were sent every other day in order to remind them to sit with the correct posture while using the backrest.
Backrest The acupressure backrest was a 16 × 16 × 1.96 pillow with 0.5 kg of kapok filling inside. There were two lateral belts at the pillow’s sides which could be locked to maintain the backrest’s correct position while attached to an office chair (see Figs. 1 and 2). The acupressure wood device was fixed at the center of the backrest and each pin was adjustable (up/down and center/lateral positions) to individual acupoint levels. The two
Figure 2 Lateral view: the acupressure backrest was set within the chair. The backrest should be close to the back region to maintain lumbar lordosis and stimulate pressure at the acupoints effectively.
most commonly used acupuncture points in the back, Urinary Bladder 23 and Urinary Bladder 25, were targeted by the device, a design derived from the literature reviews. UB23; a powerful point for treating conditions such as LBP, kidney dysfunction, abnormal menstruation, insomnia, indigestion, erectile dysfunction, urogenital disorders, sciatica, ear disorder, nephritis, and abnormal bladder contraction25,26 is away from the lower edge of the second lumbar spinous process (L2) to the lateral side by 1.5 cun*. UB25, which reduces LBP and other conditions such as bowel inflammation, diarrhea, constipation, abdominal distention, sciatica, constipation,26,27 is away from the lower edge of the fourth lumbar spinous process (L4) spinous process to the lateral side by 1.5 cun (1 cun = the width of interphalangeal joint of the thumb at its widest point).
Outcome measurement A series of valid and reliable outcome measures were used to determine the different aspects of factors related to LBP. Three subjective outcome measurements were completed by participants independently: the Visual Analog Scale (VAS)28 for pain, the Roland-Morris Disability Questionnaire (RMDQ)29 for function and disability and the Global Perceived Effect30 for measurement of patient’s satisfaction after the treatment. Most outcome measurements with exception of the global perceived effect — were measured in all groups at baseline and follow-up measurements after 2 weeks, 4 weeks and follow up at 3 months.
Statistical analysis All data were analyzed using the Statistical Package for the Social Sciences (version 17.0). Descriptive statistics such as mean and standard error of the mean were calculated and reported. The significant differences of participants’ characteristics and outcomes between the randomized groups (control and backrest) and the backrest (randomized and preferred) groups were analyzed using one way analysis of variance (ANOVA) or analysis of covariance (ANCOVA), using pretreatment value as the covariate, at 2-week, 4-week of the backrest and 3-month follow-up. The Kruskal—Wallis and Mann—Whitney tests were applied to data with non-normal distributions. For the randomized groups (control and backrest), the significant change within group over time was determined by using a two-way repeated-measures ANOVA with two related factors: group and time. The level of significance for all tests was set at 0.05. The effect size was
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N. Purepong et al. Assessed for eligibility (n=236) Excluded (n=135) declined to participate Randomized (n=64)
Control group (n=32)
9 Received allocated control 10 group (n=32)
Acupressure backrest group (n=32)
Acupressure backrest group (n=37)
Received allocated acupressure backrest group (n=32)
Received preferred acupressure backrest group (n=37)
12 Received allocated control group (n=32) 13
Received allocated acupressure backrest group (n=32)
Received allocated 15 control group (n=32) 16
Received allocated acupressure backrest group (n=32)
18 Received allocated control group (n=32) 19
Preferred (n=37)
Received preferred acupressure backrest group (n=37) Received preferred acupressure backrest group (n=37)
Received preferred acupressure backrest group (n=37)
Received allocated acupressure backrest group (n=32)
Figure 3
Flow chart of patient disposition in the trial.
calculated to determine any changes in size of treatment effects between groups. Additionally, the number of individuals achieving a minimal clinically significant improvement, as defined by Ostelo et al.31 (30% improvement for pain and disability) were explored. The satisfaction results were analyzed by the percentage of all participants measured at each level of the variable.
Results Participant flow is shown in Fig. 3. A total of 101 participants completed the baseline questionnaires and were included in the study. The participants included 79 female and 22 male office workers aged between 23 and 60 years with 22.38 ± 0.23 kg/m2 of averaged body mass index. The baseline demographic characteristics between groups were well balanced (P > 0.05) with the exception of VAS scores between the randomized groups (P = 0.010). The baseline data of demographic characteristics and outcome measures is summarized in Table 1.
Between-group comparisons Randomized acupressure backrest vs. control Table 2 reveals the results during the 4-month study period. For VAS scores, there were significant effects on pain among the experimental groups after controlling the pain effect at baseline, F(2, 95) = 5.645 (P = 0.005) and F(2, 95) = 14.478 (P < 0.001) (at 4 week and 3 month follow-up, respectively). Significant differences between control and randomized acupressure backrest groups were found at 4 weeks of the backrest use (P = 0.004, effect size = 0.825) and at 3 month
follow-up (P < 0.001, effect size = 1.820). For RMDQ scores, significant effects were found on disability at the P < 0.05 level for the three experimental groups, F(2, 98) = 6.586 (P = 0.002) and F(2, 98) = 14.478 (P < 0.001) (at 2 week and 3 month follow-up, respectively). The significant differences of the RMDQ scores between control and randomized acupressure backrest groups appeared at 2 week of the backrest use (P = 0.032, effect size = 0.593) and 3 month follow-up (P < 0.001, effect size = 0.879).
Preference effects (randomized acupressure backrest vs. preferred acupressure backrest) No significant difference was found between the preferred and randomized group (P > 0.05) during the period of backrest use as well as follow-up. This indicated that the preference had no significant effect on these outcomes.
Within-group comparisons Pain and disability scores in the backrest group decreased at each time point during the treatment and follow-up. A two-way repeated ANOVA revealed that the decreases over time were significant, F(3, 93) = 12.56 (P < 0.001) and there was a significant interaction between group and time F(3, 93) = 26.28 (P < 0.001. Changes of the mean scores over time were reported in Figs. 4 and 5. The mean differences of VAS and RMDQ outcomes for the acupuncture backrest group exceeded the Minimal Clinically Important Change (MCIC) (30% improvement of baseline pain and disability: 1.56 for VAS, 1.92 for RMDQ) at all three time points.
Baseline characteristics of the study population. Randomized control (n = 32)
Demographic characteristics Age (mean ± SEM) Body mass index (kg/m2 )
Preferred acupressure backrest (n = 37)
Bonferroni
P
Control vs. randomized backrest
Randomized vs. preferred backrest
39.97 ± 1.86 22.43 ± 0.48
39.81 ± 1.73 22.64 ± 0.43
41.46 ± 1.72 22.10 ± 0.31
0.759 0.631
1.000 1.000
1.000 1.000
3.70 ± 0.35 4.81 ± 0.57
5.19 ± 0.32 5.81 ± 0.73
5.37 ± 0.35 5.73 ± 0.73
0.001* 0.897
0.010* 1.000
1.000 1.000
Outcome measurement Baseline VAS (0—10) Baseline RMDQ (0—24) *
Randomized acupressure backrest (n = 32)
P value <0.05, VAS: visual analog scale, RMDQ: Roland-Morris disability questionnaire, and SEM: standard error of mean.
Table 2
LBP-related pain and disability, according to the received acupressure backrest group.
Outcome measured
Randomized control
Randomized acupressure backrest
Preferred acupressure backrest
P
Bonferroni/Mann—Whitney tests Control vs. randomized backrest
Subjective outcomes Mean (SEM) VAS (0—10) 2 weeks 4.008(0.347) 4 weeks 4.122(0.377) 3-Month follow-up 5.723(0.334)
2.854(0.310) 2.455(0.337) 2.455(0.299)
2.566(0.292) 1.804(0.317) 2.257(0.281)
0.414 0.005* <0.001*
RMDQ (0—24) 2 weeks 4 weeks 3-Month follow-up
4.188(0.560) 3.813(0.569) 3.375(0.547)
3.568(0.520) 3.027(0.529) 3.108(0.508)
0.002* 0.010* <0.001*
6.250(0.560) 5.406(0.569) 6.281(0.547)
Effect size
Randomized vs. preferred backrest
Effect size
— 0.004* 0.000*
0.620 0.825 1.820
— 0.488 1.000
0.163 0.354 0.123
0.032* 0.151 <0.001 *
0.593 0.473 0.879
1.000 0.944 0.729
0.200 0.224 0.086
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VAS scores were adjusted for baseline values on the pain outcome using ANCOVA. * P value < 0.05, a dash (−) indicates that the test was not administered, = the results from the Krukal—Wallis test, = the results from the Mann—Whitney test, VAS = visual analog scale, RMDQ = Roland-Morris disability questionnaire, and SEM = standard error of mean.
The effect of an acupressure backrest on pain and disability in office workers with chronic low back pain
Table 1
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Figure 4 Mean differences of VAS scores from baseline and at each time point. The negative values denote increased pain intensity; % = the percentage of participants who achieved the MCID, VAS = visual analog scale, CI = confidence interval, 2w = at 2-week after backrest use, 4w = at 4-week after backrest use, 3m = at 3-month follow up.
Backrest satisfaction Seventy-five percent and 65 percent of participants in the randomized and preferred backrest groups, respectively, reported their back pain symptom improved after 1 month (see Table 3). Five participants appeared to have worsened slightly. However, no reports of ‘Much worsen’ or ‘Worse than ever’ were recorded from participants in the backrest groups.
Discussions The study results indicated that the acupressure backrest had significant effects on pain and disability which were better than the control (P < 0.05) at the 2nd week (for disability) and at the 4th week (for pain) after the backrest use. Significant differences were also found within both groups for a 3 month follow-up (P < 0.05) with an increase of the treatment
Figure 5 Mean differences of RMDQ scores from baseline to each time point. The negative values denote increased pain intensity; % = the percentage of participants who achieved the MCID, RMDQ = Roland-Morris disability questionnaire, CI = confidence interval, 2w = at 2-week after backrest use, 4w = at 4-week after backrest use, 3m = at 3-month follow up.
N. Purepong et al. effect sizes. Both pain and disability scores showed greater improvement than the MCIC after usage of the acupressure backrest all time points measured. Over half of participants in the backrest groups were satisfied with the backrest as a treatment modality for reducing LBP symptoms. Regarding the preference effect, there was no significant difference between the randomized and preferred groups (P > 0.05) at all time point measured. One of the main patient-based outcomes for determining the LBP of office workers is the functional disability.32 It was recommended for patients when evaluating the research and patients in clinics.32 Several researchers gave more weight to functional disability.33—35 And many studies concerning LBP adopted RMDQ as a primary outcome.20,36,37 For office workers, patients need to return to work quickly due to economic burden. They should not stay off work and were encouraged to do their activities of daily living as soon as possible despite continuing pain38 in order to keep the range of motion and to prevent a risk of complication. Therefore, functional disability seems more crucial. This study indicated significant reduction of the functional disability in the LBP office workers with the medium/large treatment effect of the acupressure backrest when compared with the control group after 3 month follow-up. The improvements from baseline were found for disability as well. It has been shown to be over the MCIC in the backrest groups over time for up to 3 months (mean changed 2.60—3.03 of RMDQ score). Comparing the treatment effect to the other studies of acupressure for LBP, the change of RMDQ scores aligned with the acupressure study by Hsieh et al.20 (mean changed 5.5 after treatment and 8.7 at 6-month compared to baseline), which indicated acupressure was more effective than other intervention. Compared to other modalities, based on the study by Cecchi et al.33 , we found changes of the mean for RMDQ at the 3rd month after treatment as follows: spinal manipulation (6.2) and back school exercise (4.2). Although there were higher reductions of RMDQ score from conventional treatment, the smaller change in our study could be achieved in the group of patients who received low active intervention, such as the acupressure backrest. For pain intensity, the significant effect of the acupressure backrest was found at 4 weeks and 3 months follow-up (effect size = 0.43 and 0.88). When compared the treatment effect size to the acupuncture treatment, we found that our approach could provided the comparable effect (effect size = 0.73)39 which indicated the acupressure backrest could be used as an alternative to the acupuncture treatment for LBP in office workers. An improvement of pain over the MCIC was shown in this study as well. This was comparable to previous studies of acupressure treatment20 (mean changed after treatment = 2.82 and at sixth month followup = 4.27 compared to baseline) and quite larger than the other conventional treatments for LBP33 (spinal manipulation = 1.4; back school exercise = 0.6, at 6th month compared to baseline). Previous studies which attempted to improve sitting posture demonstrated that the use of backrest with lumbar support was able to improve LBP symptoms more than not using a backrest (P < 0.05).10,11,15 Sitting with lumbar support resulted in reduced sitting load on the lumbar spine and reduced lumbar muscular activity, which may
The effect of an acupressure backrest on pain and disability in office workers with chronic low back pain Table 3
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Participant’s satisfaction.
Satisfaction
1 = completely recovered 2 = much improved 3 = slightly improved 4 = no change 5 = slightly worsened 6 = much worsened 7 = worse than ever
Acupressure backrest patients Randomization n (%)
Preference n (%)
0 5(15.63) 19(59.38) 5(15.63) 3(9.38) 0 0
0 9(24.32) 15(40.54) 11(29.73) 2(5.41) 0 0
n = number of participants.
potentially reduce sitting-related LBP.15 To utilize acupressure as a treatment modality for office workers who engage in prolonged sitting, the newest acupressure backrest had been proposed. The acupressure device is adjustable to individual users at the exact spinal level and also the distance from midline. According to traditional Chinese medicine (TCM), possible explanations for the effectiveness of the acupressure point device for LBP was improved yin-yang balance, relaxed muscles and improved back pain.25,40,41 Also, lumbar pain is said to be caused by either external trauma, or by internal deficiency of antipathogenic vital energy (Qi) and external invasion by wind-cold or cold-damp, resulting in obstruction of Qi and blood in the meridians.41 Applying pressure at BL 23 and BL 25 can tonify the Qi energy, invigorate blood supply in the back area (Shu points),40 strengthen the kidneys, benefit the essence and strengthen the lower back.42 Preference was also a factor that has been explored for its influence on outcomes in LBP clinical trials.23 Previous studies regarding LBP showed that the treatment preference influenced the outcome.43,44 However this study yielded different results which could be a product of the different types of intervention and the patients’ conditions. Our study suggested that preference for treatment is not always a powerful factor in treatment effects. These findings were supported by the studies with acupuncture for knee pain,45 acupuncture vs. midazolam for gastroscopy46 and cognitive therapy for panic disorder.47 This is the first study which applied the specific lumbar backrest with stimulating acupuncture points in the lumbar region, resulting in diminished pain and functional disability over time. Otherwise we investigated the patient preference to confirm treatment effects of such outcomes in the randomized group. Admittedly, there were some study limitations. The VAS baseline scores between groups were significantly differences, therefore, adjusted means were used to explore the between-group differences. Future study should be conducted using a randomized block design in order to equalize across the two arms.22 Moreover, patient- and therapist-blinded methods are impossible for this design, while an assessor-blinded method could be considered using the objective outcome measure. Also, the follow-ups should be extended up to 1 year in order to determine the prolonged effect of treatment intervention for LBP patients.
Conclusion This study has provided new insight into the use of backrests as treatment for office workers suffering from LBP. The study findings suggested that a backrest with stimulating acupoints could improve the LBP conditions, and the majority of users were satisfied with the treatment. Moreover, the cost of a backrest was relatively low when compared to other instruments. This could prove useful, as it may give insight into the utility of combining acupressure points with ergonomic chair designs to help LBP while performing seated tasks.
Conflict of interest statement None declared.
Funding This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.
Acknowledgements We would like to acknowledge the funding source of this research: The Chulalongkorn University Centenary Academic Development Project — 12. Also, our sincere thanks go to Chulalongkorn University, Transport Co., Ltd., the Department of Medical Sciences in the Ministry of Public Health, and the Ministry of Education for help and support in recruiting participants with chronic LBP.
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N. Purepong et al. 25. Filshie J, White A. Medical acupuncture: a western scientific approach. Edinburgh: Churchill Livingstone; 1998. 26. Maciocia G. The practice of Chinese medicine. New York: Churchill Livingstone; 1994. 27. Stux G, Berman B, Pomeranz B. Basics of acupuncture. New York: Springer; 2003. 28. Ohnhaus EE, Adler R. Methodological problems in the measurement of pain: a comparison between the verbal rating scale and the visual analogue scale. Pain 1975;1(4):379—84. 29. Roland M, Morris R. A study of the natural history of back pain. Part I: development of a reliable and sensitive measure of disability in low-back pain. Spine 1983;8(2):141—4. 30. Ostelo RW, de Vet HC. Clinically important outcomes in low back pain. Best Pract Res Clin Rheumatol 2005;19(4): 593—607. 31. Ostelo RW, Deyo RA, Stratford P, Waddell G, Croft P, Von Korff M, et al. Interpreting change scores for pain and functional status in low back pain: towards international consensus regarding minimal important change. Spine 2008;33(1):90—4. 32. Bombardier C. Outcome assessments in the evaluation of treatment of spinal disorders: summary and general recommendations. Spine 2000;25(24):3100—3. 33. Cecchi F, Molino-Lova R, Chiti M, Pasquini G, Paperini A, Conti AA, et al. Spinal manipulation compared with back school and with individually delivered physiotherapy for the treatment of chronic low back pain: a randomized trial with one-year followup. Clin Rehabil 2010;24(1):26—36. 34. Taechaarpornkul W, Suvapan D, Theppanom C, Chanthipwaree C, Chirawatkul A. Comparison of the effectiveness of six and two acupuncture point regimens in osteoarthritis of the knee: a randomised trial. Acupunct Med 2009;27(1):3—8. 35. Foster NE, Thomas E, Barlas P, Hill JC, Young J, Mason E, et al. Acupuncture as an adjunct to exercise based physiotherapy for osteoarthritis of the knee: randomised controlled trial. BMJ 2007;335(7617):436. 36. Jellema P, van der Windt DA, van der Horst HE, Twisk JW, Stalman WA, Bouter LM. Should treatment of (sub) acute low back pain be aimed at psychosocial prognostic factors? Cluster randomised clinical trial in general practice. BMJ 2005;331(7508):84. 37. UK BEAM Trial Team. United Kingdom back pain exercise and manipulation (UK BEAM) randomised trial: effectiveness of physical treatments for back pain in primary care. BMJ 2004;329(7479):1377. 38. Roland M, Waddell G, Moffett JK, Burton K, Main C. The back book. second ed. London: The Stationery Office; 2002. 39. Yuan QL, Guo TM, Liu L, Sun F, Zhang YG. Traditional Chinese medicine for neck pain and low back pain: a systematic review and meta-analysis. PLoS ONE 2015;10(2):e0117146, http://dx.doi.org/10.1371/journal.pone.0117146. 40. Kaptchuk TJ. Acupuncture: theory, efficacy, and practice. Ann Intern Med 2002;136(5):374—83. 41. Macpherson H. The treatment of neck and upper back pain with acupuncture. JCM 1992;38:22—6. 42. Focks C. Atlas of acupuncture. English ed. Philadelphia: Churchill Livingstone; 2008. 43. Johnson RE, Jones GT, Wiles NJ, Chaddock C, Potter RG, Roberts C, et al. Active exercise, education, and cognitive behavioral therapy for persistent disabling low back pain: a randomized controlled trial. Spine 2007;32(15):1578—85. 44. Goldstein MS, Morgenstern H, Hurwitz EL, Yu F. The impact of treatment confidence on pain and related disability among patients with low-back pain: results from the University of California, Los Angeles, low-back pain study. Spine J 2002;2(6):391—401. 45. Witt CM, Jena S, Brinkhaus B, Liecker B, Wegscheider K, Willich SN. Acupuncture in patients with osteoarthritis of the knee or
The effect of an acupressure backrest on pain and disability in office workers with chronic low back pain hip: a randomized, controlled trial with an additional nonrandomized arm. Arthritis Rheum 2006;54(11):3485—93. 46. Melchart D, Steger HG, Linde K, Makarian K, Hatahet Z, Brenke R, et al. Integrating patient preferences in clinical trials: a pilot study of acupuncture versus midazolam for gastroscopy. J Altern Complement Med 2002;8(3):265—74.
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The effect of an acupressure backrest on pain and disability in office workers with chronic low back pain: A randomized, controlled study and patients’ preferences Nithima Purepong ∗, Sirinant Channak, Sujitra Boonyong, Premtip Thaveeratitham, Prawit Janwantanakul Department of Physical Therapy, Faculty of Allied Health Sciences, Chulalongkorn University, Bangkok, Thailand Available online 18 March 2015
KEYWORDS Low back pain; Backrest; Acupressure
Summary Objective: This study investigated the effects of an acupoint-stimulating lumbar backrest on pain and disability in office workers who suffering from low back pain (LBP) as well as the preference influence on pain and disability. Methods: Sixty-four participants were randomly assigned to two groups: one with no intervention (n = 32) and another with 1 month of backrest use (n = 32). An additional group (n = 37) who wished to try 1 month of acupressure backrest were recruited to indicate the preference effect. Pain and disability were two key outcomes. Results: Significant differences between control and randomized acupressure backrest groups were found at 2 week period for disability and at 4 weeks for pain after the backrest use. Also, significant differences were found in both groups for 3 month period with an increase of the treatment effect on pain and disability. Both control and randomized acupressure backrest groups showed greater improvement in pain and disability scores which were more than the minimal clinically important change (30% improvement for both outcomes). No significant difference was found for pain and disability between the randomized and preferred backrest groups. Conclusion: These findings suggested 1-month of acupressure backrest use could improve LBP conditions. Preference was not a powerful moderator to the significant treatment effect. © 2015 Elsevier Ltd. All rights reserved.
∗
Corresponding author. Tel.: +66 2 218 3767; fax: +66 2 218 3766. E-mail addresses: [email protected] (N. Purepong), [email protected] (S. Channak), [email protected] (S. Boonyong), [email protected] (P. Thaveeratitham), [email protected] (P. Janwantanakul). http://dx.doi.org/10.1016/j.ctim.2015.03.005 0965-2299/© 2015 Elsevier Ltd. All rights reserved.
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Introduction Low back pain (LBP) is the most common musculoskeletal disorder. Incidences of LBP are growing and creating an economic burden for society.1 The total costs of LBP in the United States exceed $100 billion per year.2 In Thailand, the reported cost of management for low back pain in Thailand was about $72.59 USD per person in one year.3 Thirty-four percent of 1428 Bangkok office workers surveyed were found to experience low back pain during a period of 12 months, which they attributed to work.4 Office workers who mostly spent prolonged periods of work seated regarded their chairs as crucial workstation equipment. Several aspects of chair design were mentioned in healthy and safety guidelines for computer ergonomics.5,6 One of the important factors for workers seated for prolonged periods is reduction of load through the lumbar spine. The reduced load could be achieved by transferring body weight through the armrests and feet as well as through the backrest.7 Backrests have become the focal point of several studies.8—10 Several designs of backrests have been proposed.11—13 The guidelines for office ergonomics recommended that a backrest should support the lumbar spine6 with have a specific size without restricting movement of the spine or upper extremity.14 Many studies were conducted to explore the effects of backrests with lumbar support while seated among normal subjects,10,11,15 but few clinical research studies involving LBP were conducted.15,16 Some of them indicated positive effects of backrests with lumbar support for LBP15 however, the treatment effect of backrests was still inconclusive. Therefore it was important and necessary to further develop the backrest and investigate its curative effects for LBP among office workers who sit for protracted periods. Acupressure, a complementary and alternative therapy, has received increasing attention for its manipulated method, which uses fingers instead of needles on the acupoints. The mechanism of pain relief under the acupressure effect is caused by increasing threshold pressure, circulating blood and reducing waste products such as substance P and histamine.17 In addition, the gate control theory of Wall and Melzack18 could explain the pain theory and the endorphin release.19 The effect of acupressure for LBP has been demonstrated by a randomized, controlled trial.20,21 Based on the knowledge of traditional Chinese medicine and the recommended use of backrests with lumbar support among office workers, a backrest with adjustable acupressure lumbar support was designed and developed for LBP-suffering office workers. The aim of this study was to investigate the effectiveness of the acupressure backrest applied for a 1-month period among office workers with chronic LBP. The randomized controlled trials are considered as the most robust method.22 However, the weakness of randomization was that the patient with low preference to intervention may participate partially or refuse the study protocol.23 Otherwise, the Preference Collaborative Review Group23 had reported that the preferences among patients in musculoskeletal trials were associated with their treatment effects. For this reason, we integrated both designs in this study in order to investigate the effect of an adjustable acupressure
N. Purepong et al. backrest on pain and disability as well as the preference effect of the acupressure backrest. Participants who preferred using the backrest were recruited to participate in this study in order to control the preference effects.
Methodology Study design A randomized, controlled study design comparing the control and acupressure backrest groups was conducted for the study. Participants who agreed to randomization were assigned to either a control group or an acupressure backrest group using the computers generating random numbers. Participants who declined to be allocated to the randomized groups were assigned to the preferred acupressure backrest group.
Participants Participants consisted of office workers who worked in government offices or public enterprise in Bangkok, Thailand. The participants were aged 20—60 years, diagnosed as having chronic non-specific LBP (≥3 months), worked in their current position for at least 1 year, sat for at least 2 h per working period, and were able to write and read Thai. Standard office chairs were used, which consisted of specific components as per recommendations from the Ministry of Labor offices, Canada6 and Chaffin et al.24 Participants were excluded if they had a BMI of >25 kg/m2 , history of nonemployment related LBP, indication of neurological deficit, traumatic spinal fracture, serious spinal diseases such as cancer or tumors, previous spinal surgery, or were pregnant. Also excluded were those who experienced bleeding from the back, or had open wounds, contusions or swelling.
Sample size Estimates of variability for the two key outcomes (pain and disability) were obtained from a pilot study and power calculation (˛ = 0.05; (1 − ˇ) = 0.90; effect size = 0.84). Based on this, 27 participants were required for each group. Allowing for 15 percent attrition by 3-month follow-up, a sample size of 32 participants per randomized group was required for this study.
Intervention The study was approved by the Chulalongkorn University Human Ethics Committee. Written consent was obtained from all participants. Participants were asked to fill out the baseline data which consisted of three self-administered questionnaires. They were requested to continue normal activities and to avoid other forms of treatment while receiving intervention. However, if participants requested another form of treatment, it was recorded by a physical therapist.
The effect of an acupressure backrest on pain and disability in office workers with chronic low back pain
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Figure 1 The acupressure backrest was composed of lumbar support with the wooden acupressure-point stimulation device (A) at the center, belt (B) and lock (C) to fix the backrest to the office chair.
Control group No intervention was provided to the control group; however, they were able to contact the physical therapist who provided the treatment if they needed advice concerning back pain for the period of one month. The physical therapist would provide standard advice and recommend appropriate posture for sitting at a work station.
Acupressure backrest group The acupressure backrest was installed onto the office chairs of participants in both the allocated and backrest groups by the same physical therapist. The physical therapist explained how to effectively sit on the office chair with the backrest. The physical therapist visited their work stations twice a week in order to check the level of the acupressure point device and position of the backrest. Also, three short message signals were sent every other day in order to remind them to sit with the correct posture while using the backrest.
Backrest The acupressure backrest was a 16 × 16 × 1.96 pillow with 0.5 kg of kapok filling inside. There were two lateral belts at the pillow’s sides which could be locked to maintain the backrest’s correct position while attached to an office chair (see Figs. 1 and 2). The acupressure wood device was fixed at the center of the backrest and each pin was adjustable (up/down and center/lateral positions) to individual acupoint levels. The two
Figure 2 Lateral view: the acupressure backrest was set within the chair. The backrest should be close to the back region to maintain lumbar lordosis and stimulate pressure at the acupoints effectively.
most commonly used acupuncture points in the back, Urinary Bladder 23 and Urinary Bladder 25, were targeted by the device, a design derived from the literature reviews. UB23; a powerful point for treating conditions such as LBP, kidney dysfunction, abnormal menstruation, insomnia, indigestion, erectile dysfunction, urogenital disorders, sciatica, ear disorder, nephritis, and abnormal bladder contraction25,26 is away from the lower edge of the second lumbar spinous process (L2) to the lateral side by 1.5 cun*. UB25, which reduces LBP and other conditions such as bowel inflammation, diarrhea, constipation, abdominal distention, sciatica, constipation,26,27 is away from the lower edge of the fourth lumbar spinous process (L4) spinous process to the lateral side by 1.5 cun (1 cun = the width of interphalangeal joint of the thumb at its widest point).
Outcome measurement A series of valid and reliable outcome measures were used to determine the different aspects of factors related to LBP. Three subjective outcome measurements were completed by participants independently: the Visual Analog Scale (VAS)28 for pain, the Roland-Morris Disability Questionnaire (RMDQ)29 for function and disability and the Global Perceived Effect30 for measurement of patient’s satisfaction after the treatment. Most outcome measurements with exception of the global perceived effect — were measured in all groups at baseline and follow-up measurements after 2 weeks, 4 weeks and follow up at 3 months.
Statistical analysis All data were analyzed using the Statistical Package for the Social Sciences (version 17.0). Descriptive statistics such as mean and standard error of the mean were calculated and reported. The significant differences of participants’ characteristics and outcomes between the randomized groups (control and backrest) and the backrest (randomized and preferred) groups were analyzed using one way analysis of variance (ANOVA) or analysis of covariance (ANCOVA), using pretreatment value as the covariate, at 2-week, 4-week of the backrest and 3-month follow-up. The Kruskal—Wallis and Mann—Whitney tests were applied to data with non-normal distributions. For the randomized groups (control and backrest), the significant change within group over time was determined by using a two-way repeated-measures ANOVA with two related factors: group and time. The level of significance for all tests was set at 0.05. The effect size was
350
N. Purepong et al. Assessed for eligibility (n=236) Excluded (n=135) declined to participate Randomized (n=64)
Control group (n=32)
9 Received allocated control 10 group (n=32)
Acupressure backrest group (n=32)
Acupressure backrest group (n=37)
Received allocated acupressure backrest group (n=32)
Received preferred acupressure backrest group (n=37)
12 Received allocated control group (n=32) 13
Received allocated acupressure backrest group (n=32)
Received allocated 15 control group (n=32) 16
Received allocated acupressure backrest group (n=32)
18 Received allocated control group (n=32) 19
Preferred (n=37)
Received preferred acupressure backrest group (n=37) Received preferred acupressure backrest group (n=37)
Received preferred acupressure backrest group (n=37)
Received allocated acupressure backrest group (n=32)
Figure 3
Flow chart of patient disposition in the trial.
calculated to determine any changes in size of treatment effects between groups. Additionally, the number of individuals achieving a minimal clinically significant improvement, as defined by Ostelo et al.31 (30% improvement for pain and disability) were explored. The satisfaction results were analyzed by the percentage of all participants measured at each level of the variable.
Results Participant flow is shown in Fig. 3. A total of 101 participants completed the baseline questionnaires and were included in the study. The participants included 79 female and 22 male office workers aged between 23 and 60 years with 22.38 ± 0.23 kg/m2 of averaged body mass index. The baseline demographic characteristics between groups were well balanced (P > 0.05) with the exception of VAS scores between the randomized groups (P = 0.010). The baseline data of demographic characteristics and outcome measures is summarized in Table 1.
Between-group comparisons Randomized acupressure backrest vs. control Table 2 reveals the results during the 4-month study period. For VAS scores, there were significant effects on pain among the experimental groups after controlling the pain effect at baseline, F(2, 95) = 5.645 (P = 0.005) and F(2, 95) = 14.478 (P < 0.001) (at 4 week and 3 month follow-up, respectively). Significant differences between control and randomized acupressure backrest groups were found at 4 weeks of the backrest use (P = 0.004, effect size = 0.825) and at 3 month
follow-up (P < 0.001, effect size = 1.820). For RMDQ scores, significant effects were found on disability at the P < 0.05 level for the three experimental groups, F(2, 98) = 6.586 (P = 0.002) and F(2, 98) = 14.478 (P < 0.001) (at 2 week and 3 month follow-up, respectively). The significant differences of the RMDQ scores between control and randomized acupressure backrest groups appeared at 2 week of the backrest use (P = 0.032, effect size = 0.593) and 3 month follow-up (P < 0.001, effect size = 0.879).
Preference effects (randomized acupressure backrest vs. preferred acupressure backrest) No significant difference was found between the preferred and randomized group (P > 0.05) during the period of backrest use as well as follow-up. This indicated that the preference had no significant effect on these outcomes.
Within-group comparisons Pain and disability scores in the backrest group decreased at each time point during the treatment and follow-up. A two-way repeated ANOVA revealed that the decreases over time were significant, F(3, 93) = 12.56 (P < 0.001) and there was a significant interaction between group and time F(3, 93) = 26.28 (P < 0.001. Changes of the mean scores over time were reported in Figs. 4 and 5. The mean differences of VAS and RMDQ outcomes for the acupuncture backrest group exceeded the Minimal Clinically Important Change (MCIC) (30% improvement of baseline pain and disability: 1.56 for VAS, 1.92 for RMDQ) at all three time points.
Baseline characteristics of the study population. Randomized control (n = 32)
Demographic characteristics Age (mean ± SEM) Body mass index (kg/m2 )
Preferred acupressure backrest (n = 37)
Bonferroni
P
Control vs. randomized backrest
Randomized vs. preferred backrest
39.97 ± 1.86 22.43 ± 0.48
39.81 ± 1.73 22.64 ± 0.43
41.46 ± 1.72 22.10 ± 0.31
0.759 0.631
1.000 1.000
1.000 1.000
3.70 ± 0.35 4.81 ± 0.57
5.19 ± 0.32 5.81 ± 0.73
5.37 ± 0.35 5.73 ± 0.73
0.001* 0.897
0.010* 1.000
1.000 1.000
Outcome measurement Baseline VAS (0—10) Baseline RMDQ (0—24) *
Randomized acupressure backrest (n = 32)
P value <0.05, VAS: visual analog scale, RMDQ: Roland-Morris disability questionnaire, and SEM: standard error of mean.
Table 2
LBP-related pain and disability, according to the received acupressure backrest group.
Outcome measured
Randomized control
Randomized acupressure backrest
Preferred acupressure backrest
P
Bonferroni/Mann—Whitney tests Control vs. randomized backrest
Subjective outcomes Mean (SEM) VAS (0—10) 2 weeks 4.008(0.347) 4 weeks 4.122(0.377) 3-Month follow-up 5.723(0.334)
2.854(0.310) 2.455(0.337) 2.455(0.299)
2.566(0.292) 1.804(0.317) 2.257(0.281)
0.414 0.005* <0.001*
RMDQ (0—24) 2 weeks 4 weeks 3-Month follow-up
4.188(0.560) 3.813(0.569) 3.375(0.547)
3.568(0.520) 3.027(0.529) 3.108(0.508)
0.002* 0.010* <0.001*
6.250(0.560) 5.406(0.569) 6.281(0.547)
Effect size
Randomized vs. preferred backrest
Effect size
— 0.004* 0.000*
0.620 0.825 1.820
— 0.488 1.000
0.163 0.354 0.123
0.032* 0.151 <0.001 *
0.593 0.473 0.879
1.000 0.944 0.729
0.200 0.224 0.086
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VAS scores were adjusted for baseline values on the pain outcome using ANCOVA. * P value < 0.05, a dash (−) indicates that the test was not administered, = the results from the Krukal—Wallis test, = the results from the Mann—Whitney test, VAS = visual analog scale, RMDQ = Roland-Morris disability questionnaire, and SEM = standard error of mean.
The effect of an acupressure backrest on pain and disability in office workers with chronic low back pain
Table 1
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Figure 4 Mean differences of VAS scores from baseline and at each time point. The negative values denote increased pain intensity; % = the percentage of participants who achieved the MCID, VAS = visual analog scale, CI = confidence interval, 2w = at 2-week after backrest use, 4w = at 4-week after backrest use, 3m = at 3-month follow up.
Backrest satisfaction Seventy-five percent and 65 percent of participants in the randomized and preferred backrest groups, respectively, reported their back pain symptom improved after 1 month (see Table 3). Five participants appeared to have worsened slightly. However, no reports of ‘Much worsen’ or ‘Worse than ever’ were recorded from participants in the backrest groups.
Discussions The study results indicated that the acupressure backrest had significant effects on pain and disability which were better than the control (P < 0.05) at the 2nd week (for disability) and at the 4th week (for pain) after the backrest use. Significant differences were also found within both groups for a 3 month follow-up (P < 0.05) with an increase of the treatment
Figure 5 Mean differences of RMDQ scores from baseline to each time point. The negative values denote increased pain intensity; % = the percentage of participants who achieved the MCID, RMDQ = Roland-Morris disability questionnaire, CI = confidence interval, 2w = at 2-week after backrest use, 4w = at 4-week after backrest use, 3m = at 3-month follow up.
N. Purepong et al. effect sizes. Both pain and disability scores showed greater improvement than the MCIC after usage of the acupressure backrest all time points measured. Over half of participants in the backrest groups were satisfied with the backrest as a treatment modality for reducing LBP symptoms. Regarding the preference effect, there was no significant difference between the randomized and preferred groups (P > 0.05) at all time point measured. One of the main patient-based outcomes for determining the LBP of office workers is the functional disability.32 It was recommended for patients when evaluating the research and patients in clinics.32 Several researchers gave more weight to functional disability.33—35 And many studies concerning LBP adopted RMDQ as a primary outcome.20,36,37 For office workers, patients need to return to work quickly due to economic burden. They should not stay off work and were encouraged to do their activities of daily living as soon as possible despite continuing pain38 in order to keep the range of motion and to prevent a risk of complication. Therefore, functional disability seems more crucial. This study indicated significant reduction of the functional disability in the LBP office workers with the medium/large treatment effect of the acupressure backrest when compared with the control group after 3 month follow-up. The improvements from baseline were found for disability as well. It has been shown to be over the MCIC in the backrest groups over time for up to 3 months (mean changed 2.60—3.03 of RMDQ score). Comparing the treatment effect to the other studies of acupressure for LBP, the change of RMDQ scores aligned with the acupressure study by Hsieh et al.20 (mean changed 5.5 after treatment and 8.7 at 6-month compared to baseline), which indicated acupressure was more effective than other intervention. Compared to other modalities, based on the study by Cecchi et al.33 , we found changes of the mean for RMDQ at the 3rd month after treatment as follows: spinal manipulation (6.2) and back school exercise (4.2). Although there were higher reductions of RMDQ score from conventional treatment, the smaller change in our study could be achieved in the group of patients who received low active intervention, such as the acupressure backrest. For pain intensity, the significant effect of the acupressure backrest was found at 4 weeks and 3 months follow-up (effect size = 0.43 and 0.88). When compared the treatment effect size to the acupuncture treatment, we found that our approach could provided the comparable effect (effect size = 0.73)39 which indicated the acupressure backrest could be used as an alternative to the acupuncture treatment for LBP in office workers. An improvement of pain over the MCIC was shown in this study as well. This was comparable to previous studies of acupressure treatment20 (mean changed after treatment = 2.82 and at sixth month followup = 4.27 compared to baseline) and quite larger than the other conventional treatments for LBP33 (spinal manipulation = 1.4; back school exercise = 0.6, at 6th month compared to baseline). Previous studies which attempted to improve sitting posture demonstrated that the use of backrest with lumbar support was able to improve LBP symptoms more than not using a backrest (P < 0.05).10,11,15 Sitting with lumbar support resulted in reduced sitting load on the lumbar spine and reduced lumbar muscular activity, which may
The effect of an acupressure backrest on pain and disability in office workers with chronic low back pain Table 3
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Participant’s satisfaction.
Satisfaction
1 = completely recovered 2 = much improved 3 = slightly improved 4 = no change 5 = slightly worsened 6 = much worsened 7 = worse than ever
Acupressure backrest patients Randomization n (%)
Preference n (%)
0 5(15.63) 19(59.38) 5(15.63) 3(9.38) 0 0
0 9(24.32) 15(40.54) 11(29.73) 2(5.41) 0 0
n = number of participants.
potentially reduce sitting-related LBP.15 To utilize acupressure as a treatment modality for office workers who engage in prolonged sitting, the newest acupressure backrest had been proposed. The acupressure device is adjustable to individual users at the exact spinal level and also the distance from midline. According to traditional Chinese medicine (TCM), possible explanations for the effectiveness of the acupressure point device for LBP was improved yin-yang balance, relaxed muscles and improved back pain.25,40,41 Also, lumbar pain is said to be caused by either external trauma, or by internal deficiency of antipathogenic vital energy (Qi) and external invasion by wind-cold or cold-damp, resulting in obstruction of Qi and blood in the meridians.41 Applying pressure at BL 23 and BL 25 can tonify the Qi energy, invigorate blood supply in the back area (Shu points),40 strengthen the kidneys, benefit the essence and strengthen the lower back.42 Preference was also a factor that has been explored for its influence on outcomes in LBP clinical trials.23 Previous studies regarding LBP showed that the treatment preference influenced the outcome.43,44 However this study yielded different results which could be a product of the different types of intervention and the patients’ conditions. Our study suggested that preference for treatment is not always a powerful factor in treatment effects. These findings were supported by the studies with acupuncture for knee pain,45 acupuncture vs. midazolam for gastroscopy46 and cognitive therapy for panic disorder.47 This is the first study which applied the specific lumbar backrest with stimulating acupuncture points in the lumbar region, resulting in diminished pain and functional disability over time. Otherwise we investigated the patient preference to confirm treatment effects of such outcomes in the randomized group. Admittedly, there were some study limitations. The VAS baseline scores between groups were significantly differences, therefore, adjusted means were used to explore the between-group differences. Future study should be conducted using a randomized block design in order to equalize across the two arms.22 Moreover, patient- and therapist-blinded methods are impossible for this design, while an assessor-blinded method could be considered using the objective outcome measure. Also, the follow-ups should be extended up to 1 year in order to determine the prolonged effect of treatment intervention for LBP patients.
Conclusion This study has provided new insight into the use of backrests as treatment for office workers suffering from LBP. The study findings suggested that a backrest with stimulating acupoints could improve the LBP conditions, and the majority of users were satisfied with the treatment. Moreover, the cost of a backrest was relatively low when compared to other instruments. This could prove useful, as it may give insight into the utility of combining acupressure points with ergonomic chair designs to help LBP while performing seated tasks.
Conflict of interest statement None declared.
Funding This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.
Acknowledgements We would like to acknowledge the funding source of this research: The Chulalongkorn University Centenary Academic Development Project — 12. Also, our sincere thanks go to Chulalongkorn University, Transport Co., Ltd., the Department of Medical Sciences in the Ministry of Public Health, and the Ministry of Education for help and support in recruiting participants with chronic LBP.
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