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   Table of Contents     
SHORT COMMUNICATION  
Year : 2019  |  Volume : 12  |  Issue : 3  |  Page : 252-264
Physical and physiological effects of yoga for an underserved population with chronic low back pain


Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, Kansas City, Missouri, USA

Click here for correspondence address and email

Date of Web Publication3-Sep-2019
 

   Abstract 


Background: Yoga has been shown useful in reducing chronic low back pain (CLBP) through largely unknown mechanisms. The aim of this pilot study is to investigate the feasibility of providing yoga intervention to a predominantly underserved population and explore the potential mechanisms underlying yoga intervention in improving CLBP pain. Methods: The quasi-experimental within-subject wait-listed crossover design targeted the recruitment of low-income participants who received twice-weekly group yoga for 12 weeks, following 6–12 weeks of no intervention. Outcome measures were taken at baseline, preintervention (6–12 weeks following baseline), and then postintervention. Outcome measures included pain, disability, core strength, flexibility, and plasma tumor necrosis factor (TNF)-α protein levels. Outcomes measures were analyzed by one-way ANOVA and paired one-tailed t-tests. Results: Eight patients completed the intervention. Significant improvements in pain scores measured over time were supported by the significant improvement in pre- and post-yoga session pain scores. Significant improvements were also seen in the Oswestry Disability Questionnaire scores, spinal and hip flexor flexibility, and strength of core muscles following yoga. Six participants saw a 28.6%–100% reduction of TNF-α plasma protein levels after yoga, while one showed an 82.4% increase. Two participants had no detectable levels to begin with. Brain imaging analysis shows interesting increases in N-acetylaspartate in the dorsolateral prefrontal cortex and thalamus. Conclusion: Yoga appears effective in reducing pain and disability in a low-income CLBP population and in part works by increasing flexibility and core strength. Changes in TNF-α protein levels should be further investigated for its influence on pain pathways.

Keywords: Brain imaging, chronic low back pain, core strength, flexibility, tumor necrosis factor-α, yoga

How to cite this article:
Colgrove YM, Gravino-Dunn NS, Dinyer SC, Sis EA, Heier AC, Sharma NK. Physical and physiological effects of yoga for an underserved population with chronic low back pain. Int J Yoga 2019;12:252-64

How to cite this URL:
Colgrove YM, Gravino-Dunn NS, Dinyer SC, Sis EA, Heier AC, Sharma NK. Physical and physiological effects of yoga for an underserved population with chronic low back pain. Int J Yoga [serial online] 2019 [cited 2019 Sep 19];12:252-64. Available from: http://www.ijoy.org.in/text.asp?2019/12/3/252/265743



   Introduction Top


Chronic low back pain (CLBP) is the most common cause of chronic pain in the United States, with over 100 billion dollars spent annually managing it.[1] Many people seek medical help including rehabilitation, surgery, and pharmacological treatments, but continue to experience extensive pain, disability, and functional limitations.[2] Maladaptive pain coping affects the outcome of different treatments.[3] Pain and fear of aggravating symptoms can be limiting factors to participation in a regular exercise program.[4],[5] Alternative approaches to decrease pain and facilitate return of function would be valuable and cost-effective.

Yoga appears to be a safe self-management intervention for participants with CLBP.[6] Many studies have shown yoga decreases pain and/or disability in people with CLBP. Participants have a significantly greater reduction in pain intensity and pain medication use following 12 weeks of a yoga program than those receiving usual care.[7] Yoga offers a holistic approach for people with various physical dysfunctions because it incorporates body awareness, breathing activities, physical posture, and meditation that have additional biopsychosocial benefits. Many intervention sessions were held over 12 weeks with significant changes in the outcome measures.[8],[9],[10],[11] The delivery of yoga reported has overwhelmingly been in group sessions led by a yoga instructor with infrequent adverse effects.[6],[12]

Individuals with CLBP have poor core stability, altered lumbopelvic posture, muscle imbalance, and faulty movement. Posture becomes mechanically faulty with an imbalance of tight and weak musculature that could benefit from activity such as yoga that targets both flexibility and strengthening. In addition, functional CLBP-related disability can have a high psychological impact, but there are few studies investigating full interplay of biopsychosocial factors and fewer yet, investigating potential mechanisms. Yoga is proposed to play a role in health by reversing the psychoimmunology of emotions.[13] The mechanism in which it works is unknown. Eight weeks of yoga training have been shown to significantly reduce serum levels of inflammatory markers including interleukin (IL)-6 in those with chronic heart failure.[14] Healthy control participants had constant tumor necrosis factor (TNF)-α levels, while participants with CLBP who received a multidisciplinary intervention had decreased levels at a 6-month follow-up.[15] However, there are competing studies suggesting that yoga practice does not alter circulating TNF-α levels in healthy or working individuals.[16],[17]

CLBP is associated with changes in brain chemistry in somatosensory, motor, dorsolateral prefrontal, and anterior cingulate cortices,[18],[19],[20],[21],[22] but no study has examined the effects of yoga on neurochemicals such as N-acetylaspartate, (NAA), a neuronal marker. The thalamus is important in mediating nociceptive inputs to the cortex, but studies have shown contradicting findings regarding changes in the gray matter volume of the thalamus.[23]

Low-income minorities with chronic pain have decreased access to treatment, which causes more disability and increases costs.[24] There is evidence that implementing a yoga program is feasible in minority populations. Retention was excellent throughout a 12-week intervention period (97%) and long-term retention was 77% in a group of 30 minority adults with moderate-to-severe CLBP.[7] A larger study reported 44%–65% of 95 CLBP participants attended once or twice weekly yoga classes for 12 weeks with a median attendance of 10–16 classes, respectively,[25] and showed effectiveness of yoga was generalized to a racially diverse, low-income population. Patients seen in safety net clinics usually do not have adequate medical coverage; thus, providing yoga as a self-management strategy is a way to address barriers and the overall health management cost in the underinsured.

The objective of this pilot study was to investigate the feasibility and potential physical and physiological mechanisms underlying yoga intervention in improving pain and function in a predominantly underserved population suffering with CLBP. Specifically, we investigated pain, disability, and the physical measures of core strength and lumbopelvic flexibility. The secondary objective was to explore potential contributions of the immune and central nervous system biomarkers of TNF-α and NAA in decreasing pain as the result of yoga intervention. Given the comprehensive nature of yoga treatment that includes breathing, meditation, and postures for core strengthening and flexibility, we hypothesized that yoga will improve pain, disability, and muscle flexibility and strength, and alter the immune and central nervous systems biomarkers.


   Methods Top


This study was a prospective quasi-experimental within-subject wait-listed control design of 6–12 weeks of no intervention followed by 12 weeks of yoga intervention. The study was approved by and followed the University's Institutional Review Board guidelines.

Participants were recruited from the hospital's family medicine clinic and word of mouth. Inclusion criteria included: history of CLBP (>3 months), pain intensity of at least 3 (on a 0–10 pain scale) and at least minimum disability (30% or more per Oswestry Disability Scale), Folstein Mini-Mental State Exam score >24, and English comprehending individuals naïve to structured yoga practice.

Exclusion criteria included: current pregnancy, glaucoma, significant or chronic decline in immune function, spinal fusion or other orthopedic surgery in the past 6 months, history of chronic neurological disorders (e.g., stroke, dementia), inability to make regular time commitments, and lack of transportation to scheduled yoga sessions. Informed written consent was obtained prior to the initial assessment.

Participants passing the standard magnetic resonance exclusion criteria were included in the brain scanning portion of the study.

Procedures

Assessments were conducted at three points: baseline (initial), the week prior to beginning the yoga intervention after 6–12 weeks of wait period of no-intervention (pre-intervention), and the week following the last yoga session (post-intervention). Brain scans were conducted pre- and post-intervention only on a small cohort of participants who met the criteria.

Assessments

A medical questionnaire was completed first, blood drawn second, and outcome measures completed in random order of questionnaires and then flexibility followed by core strength. The primary outcomes were pain, disability, muscle strength, and flexibility. An 11-point Numeric Rating Scale indicated pain intensity[26] and the Oswestry Low Back Pain Disability Questionnaire was used to measure disability.[27] Isometric core strength was measured for back extensors, upper abdominals, and lower abdominals by recording hold time for each position.[28] Spinal range of motion (ROM) during a forward bend was measured by the distance from fingertips to floor bending forward without bending at the knees.[29] Hip flexibility included standard goniometric measures of the hamstrings during a straight leg raise and the hip flexors measured in side lying. Outcome assessments were completed by blinded research personnel.

Immune biomarker

TNF-α levels were obtained from 5 ml standard blood draws into nonheparinized covered test tubes that were immediately cooled and processed for serum using standard protocol with final storage at −80°F. Serum protein levels were determined by protein assay analysis using a commercial ELISA kit (ALPCO, Salem, NH).

Brain spectroscopy

Brain images were acquired with a 3 Tesla scanner (Skyra scanner; Siemens Medical Solutions, Erlangen, Germany). Each scan comprised structural MR and MR spectroscopy images, using previously published protocol[20] with the total acquisition time of about 60 min. MR spectroscopy included two imaging slabs, dorsolateral prefrontal cortex (DLPFC), and thalamus using a developed protocol.[20] Two univoxel DLPFC slabs were selected in the frontal lobe (Brodmann area 46) representing the right and left side and sampling both white and gray matter. Similarly, two univoxel thalamus slabs (right and left sides) were identified from the anatomical landmarks. Acquisition time for each slab was approximately 10 min. Neurochemical concentration of NAA was analyzed according to previously published protocol.[20]

Intervention

Hatha yoga sessions with a therapeutic focus were held two times weekly for 60 min sessions directed by a certified master yoga instructor. Each session began with deep breathing exercises and relaxation techniques progressing to poses designed to begin with stretching and move into strengthening [Table 1]. The session ended with meditative relaxation. The first weekly session emphasized restorative poses and the second session was more movement based. The predesigned yoga program progressed from simple to more challenging poses over the 12-week course. Modification for restricted movement or painful positions was provided as needed. Safety issues were monitored using Common Terminology Criteria for Adverse Events version 3.0.
Table 1: Yoga program

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Statistical analysis

Data were analyzed using Sigma Plot 11.0 (Systat Software Inc., San Jose, CA, USA). Feasibility of participant recruitment and retention and adherence to intervention and adverse events were assessed by descriptive analysis. Descriptive statistics (mean, standard deviation, median, range, and 95% confidence interval for the mean difference) were calculated. Repeated-measures ANOVA was used to detect changes over time with a P = 0.05 significance level with post hoc analysis using Holm–Sidak method for all pair-wise multiple comparisons. If the sample size was not sufficient with the repeated-measures design, secondary analysis on the main interest of pre- and post-intervention changes from preintervention assessment and postintervention assessment was done using paired one-tailed t-tests. If normality failed, a Wilcoxon signed-rank test was used.


   Results Top


Twelve participants were enrolled within a 3-month period but eight participated in the intervention [Figure 1]. Loss of participants occurred prior to the 1st week of yoga intervention. There were seven females and one male ranging in age of 23–60 with the mean age of 45.63 ± 14.55 years. The overall attendance rate was 79.7%. One participant missed 33.3% of the sessions due to out-of-town work obligations. No adverse events were reported. The cohort completed 12 weeks of yoga with 100% retention rate.
Figure 1: CONSORT Diagram: Over 3 months, 12 participants were recruited with 8 completing the study

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Significant differences were found following the yoga intervention in the primary outcome measures of pain and disability. Intensities of present pain, weekly average, weekly best, and weekly worst all significantly improved [Figure 2]a. Significant improvements in pain scores measured over time (P < 0.001) were recorded before/after most classes [Figure 2]b, P ≤ 0.001]. Significant improvement was found in Oswestry Disability Index scores [Figure 3] from pre- to post-yoga (P = 0.028) and over time (P = 0.005).
Figure 2: Pain Scores. (a) Pain intensity shows significant improvements over time (ANOVA) in all pain at P < 0.001. Pain 1 = present pain, pain 2 = weekly average pain intensity, pain 3 = weekly best pain intensity and pain 4 = weekly worst pain intensity. (b) Present pain intensity on a 1–10 scale measured immediately before and after yoga sessions (n = 20) showed a significant reduction P ≤ 0.001 with a t-test

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Figure 3: Oswestry Disability Scale. Disability scores improved over time P = 0.005 as measured by ANOVA

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Upper and lower abdominal strength (P = 0.008 and P = 0.031, respectively) [Figure 4] demonstrated significant improvement following the intervention with a positive trend in back extensor strength (P = 0.078). Likewise, spinal and hip flexor flexibility improved significantly following yoga intervention (P = 0.002, P = 0.024 right hip; P = 0.05 left hip, respectively). Hamstring flexibility did not show significant improvements.
Figure 4: Core Strength Measures. Upper abdominal strength showed the most improvement over time (P = 0.055) with significance in pre-post measures (P = 0.008). Lower abdominal strength showed a trend over time (P = 0.085) with significance in pre-post measures (P = 0.031). The improvements in back extensor strength were not significant but showed a trend in improvement (P = 0.078)

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Overall TNF-α protein level changes did not reach a level of significance [Figure 5]. Two of the eight participants had undetectable levels. Five of the remaining six participants had decreased; ranging 28.57%–100%, averaging 76.2%, and the one outlier had a large increase (82.41%).
Figure 5: Serum TNF-α levels. Two participants who did not have detectable levels are not shown. Five of six participants showed a reduction in TNF-α levels following yoga intervention, while one outlying participant showed a large increase over time including the preintervention assessment

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Brain spectroscopy results showed a general trend in NAA upregulation bilaterally in the DLPFC and thalamus [Table 2]. Due to the limited number of participants included (n = 3), traditional statistical analysis was not performed. Of the three participants, one participant had high baseline NAA concentration in the right DLPFC that decreased following yoga intervention. Second, the signal-to-noise ratio was too high to obtain NAA concentration in the left DLPFC in that participant, and the participant had unusually low level of NAA in the left thalamus at baseline. Another participant also had high signal-to-noise ratio in the right thalamus following yoga training.
Table 2: Brain spectroscopy N-acetylaspartate levels

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   Discussion Top


This study investigated the feasibility and potential physical and physiological mechanisms underlying yoga intervention in improving pain and function in a predominantly underserved population suffering with CLBP. While a few studies have looked at spinal flexibility,[30],[31],[32] this study is unique in assessing core strength in combination with measuring inflammatory markers and brain changes as potential underlying mechanisms contributing the effectiveness of a yoga intervention. No study has used brain spectroscopy or TNF-α to examine the effects of yoga in CLBP. Very few studies have looked at measures of core strength in a yoga program,[33],[34] and none are in a CLBP population.

Feasibility

A 12-week group yoga program in an underserved population appears feasible with improvements in pain, disability, spinal flexibility, and core strength and some interesting changes in physiological biomarkers. Previous findings of yoga for the management of CLBP in an underserved minority population show a 44%–65% treatment adherence rate for two versus one sessions, respectively.[25] We report 100% retention rate during the intervention phase and 79.7% treatment adherence of twice-weekly group yoga over 12 weeks of intervention. All participants were recruited in 3 months, and only 4 eligible participants declined to participate. There were no adverse events or side effects from participation in yoga. These findings support the potential use of yoga as a viable treatment option for the underserved population to manage CLBP.

Pain and disability

Yoga improved all measures of pain intensity over time and showed immediate decrease in pain intensity following each yoga session. Participants subjectively reported progressively longer duration of pain relief following yoga sessions. These findings agree with most previous studies where 7 days–12 weeks of yoga decreased pain and pain behavior.[35],[36],[37],[38] Yoga intervention also had greater impact on pain intensity at 6-month follow-up compared to conventional exercise program[39] and was found to be as effective as physical therapy.[36] Since pain is the primary complaint for seeking medical care that may not be accessible or utilized, our results support yoga as an alternative intervention for CLBP for underserved individuals.

By decreasing pain, participants may be more likely to return to work and participate in activities they once avoided. We report an average 40% improvement in disability ratings. Multiple studies show 1–16 weeks of yoga result in significantly lower short-term back-specific disability.[40] Research supports many different styles of yoga, including Hatha, Iyengar, Viniyoga, and unspecified types to decrease functional disability.[41] The fact that many different styles of yoga are included suggests that the principles emphasized in yoga are more important than any specific sequence of postures.

Physical measures

Recent literature suggests that yoga can increase function in those with CLBP through improvements in strength, flexibility, and balance. Improvements in strength, flexibility, and balance after yoga are made because of the emphasis on physical postures, breathing techniques, relaxation, and meditation.[11],[31] We found an improvement in spinal and hip flexor flexibility following yoga, suggesting that yoga contributes to better physical function and less disability. Hamstring flexibility was the only ROM measure that did not significantly improve which could be due to the participants having flexibility close to the normal measurements for healthy peers.[42]

One novel aspect of our study is improvement in core muscle strength. Upper abdominal strength showed the largest improvement and a positive trend in back extensor strength was noted. Improvement in core strength could be attributed to improvement in lumbar stabilization, thereby reducing pain. Further studies are needed to investigate the independent effects of yoga on trunk muscles for pain modulation. Interestingly, the tests used for core muscle strength were terminated due to pain at pre-yoga assessment sessions and were terminated due to fatigue at post-yoga session.

Biological mechanisms

Five of six participants with detectable serum TNF-α levels had maintained or decreased levels from baseline to preintervention and a showed further decrease following yoga intervention. TNF-α is a cytokine implicated in many different diseases, but specific pathophysiology is unknown, although people with CLBP due to disc herniation have altered serum cytokine levels, specifically IL-6 and TNF-α.[43] An inflammatory process other than CLBP could have produced the observed outlier. Our findings are in contrast with a recent study showing TNF-α levels maintained in premenopausal middle-aged women with CLBP who performed a 12-week yoga program, whereas the TNF-α levels significantly increased over time in the control group.[44] Our results align with a study of overweight people with chronic inflammatory conditions such as diabetes observing reduced serum TNF-α levels in those who underwent a 2 hours daily yoga for 10 days.[45]

Although a small sample size was eligible for the MR spectroscopy, the preliminary results showed a positive trend in increase in NAA in DLPFC and thalamus. Low NAA in previous studies of people with CLBP has been interpreted as neurodegeneration[19],[22],[46] or neuronal metabolic dysfunction.[47],[48] This study is the first to observe the levels of neurochemicals associated with a yoga intervention, so the upregulation found in the DLPFC and thalamus are notable. Future research involving a larger sample is warranted to determine the significance of outcomes and to determine whether yoga has positive effect on neurodegeneration and immune dysfunction seen in CLBP. Although it is unclear how CLBP and yoga may be influenced by changes in TNF-α and NAA upregulation, the medial prefrontal cortex is thought to coordinate autonomic and behavioral stress responses.[49] Elevated TNF-α levels appear to correlate to high pain scores in thoracic disc herniations,[50] and it is thought that TNF-α is one of the pro-inflammatory cytokines involved in neuropathic pain through a GABAergic mechanism.[51] Immune cells are recruited in response to injury and could induct the sensitization of peripheral nociceptors, thus beginning a complex interactive network of inflammatory mediators, neurotransmitters, immune cells, neurons/support cells that synchronizes immune responses, and pain pathway modulation.[52] The beneficial effects of long-term yoga on stress responses, especially C-reactive protein and serum IL-6 levels,[53][67] highlights the potential benefits of yoga on the immune system. Future studies of the effect of yoga on the interplay between central nervous system pain regulation and immune responses are certainly warranted.

Limitations

The primary limitation of this study was the limited participant number needed for generalizability of the results. The lack of group difference in TNF-α levels and back extension strength could be due to small sample size. The wait list design lacks a true control group and is not conducive to participant blinding. Yoga sessions were performed in groups resulting in no control for socialization. Gender bias may be present because all but one participant completing the study were female. Due to testing facility scheduling, the time of day outcomes was taken were variable between participants. Results found here should be confirmed in a large randomized control study. Despite the limitations, the detection of changes in TNF-α and MR spectroscopy scans illuminate potential explanations for beneficial effects of yoga.


   Conclusion Top


Yoga is effective in reducing pain and disability in those with CLBP and in part works by increasing flexibility and core strength. Brain spectroscopy and TNF-α changes should be further investigated for influence on pain pathways. The use of yoga appears to be a viable supplement to basic medical treatment in low-income patient populations, where many barriers to health care are present. A larger study is feasible and warranted.

Acknowledgments

An Interprofessional Clinical Research Grant from KUMC School of Health Professionals to Yvonne Colgrove and Neena Sharma and a Frontier's Trail Blazer award to Neena Sharma supported this research. These committees had no role in the study's design, conduct, or reporting. We would like to thank Dr. Joseph Le Master for advice on research design and recruitment efforts, Kelly Colln for providing expert yoga consultation for program design and yoga intervention, Susan Harp fill in yoga instructor, Zaid Mansour for MR spectroscopy acquisition, JoAnn Lierman for blood draws, Michelle Winter for ELISA analysis, and Sevana Haghverdian for assisting with outcome measures.

Financial support and sponsorship

University of Kansas Medical Center School of Health Professions to Yvonne Colgrove and Neena Sharna and the Frontier's Trail Blazer award to Neena Sharma, as well as the use of the University of Kansas Medical Center Hoglund Brain Imaging Center for taking outcome measures including blood draws and brain images and the Kansas Intellectual and Developmental Disabilities Research Center for ELISA analysis.

Conflicts of interest

There are no conflicts of interest.



 
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Correspondence Address:
prof Yvonne M Colgrove
Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, 3901 Rainbow Boulevard, Mail Stop 2002, Kansas City 66160, Missouri
USA
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijoy.IJOY_78_18

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