Mud Therapy Combined with Core Exercise for Chronic Nonspecific Low Back Pain: A Pilot, Single-Blind, Randomized Controlled Trial.

Background Low back pain (LBP) is common in the elderly and an appropriate intervention for LBP management should be investigated. The aim of this study is to investigate the potential of mud-heat intervention combined with core exercise as an alternative intervention for relieving pain and improving motor function in individuals with nonspecific chronic LBP. Methods Thirty-one individuals with chronic nonspecific LBP were randomly allocated to either the intervention group (n = 16) or the control group (n = 15). The intervention group used a mud pack for 30 min and performed a core-exercise program for 50 min twice a day for 4 days (8 sessions). The control group performed the core-exercise program only, at the same time point as the intervention group. Pain intensity was assessed using a 100 mm visual analog scale and a pain pressure threshold (PPT) as the primary outcomes. The secondary outcome measures included functional disability by LBP (Oswestry Disability Index), muscle properties, and static/dynamic balance. Results There was a significant group difference in pain intensity at rest (p=0.048) and in the PPT at the two sites assessed (2 cm lateral to L3 spinous process, p=0.045; 2 cm lateral to L5 spinous process, p=0.015). No group differences were found in terms of muscle properties. Compared to core exercise only, moor-heat therapy and core exercise showed a significant improvement in static balance (p=0.026) and dynamic balance (p=0.019). Conclusion Mud therapy combined with core exercise is effective in relieving pain and improving motor function in patients with chronic nonspecific LBP. Further research is needed to underpin these preliminary results.


Background
Low back pain (LBP) is very common, with an estimated 40% to 80% of individuals experiencing LBP over the course of their lives [1]. e majority of LBP is nonspecific (approximately 90% of cases), and nonspecific LBP is a common health problem that most people of all ages suffer from at some point [2]. It is known that nonspecific LBP is associated with a decreased range of motion (ROM), muscle strength, and flexibility of the lumbar and hip joints [3], which can result in tension, soreness, and stiffness. ese changes induced by nonspecific LBP can lead to functional limitations in daily living activities and a decrease in quality of life [4]. Currently, there are no interventions to cure chronic LBP, but there are both pharmacologic and nonpharmacologic interventions for the improvement of LBP and its related functional problems [2]. e commonly prescribed medications for LBP management are nonsteroidal anti-inflammatory drugs (NSAIDs), skeletal muscle relaxants, and opioid analgesics [5,6]; however, adverse effects related to the long-term use of these medications have been reported [2]. A previous Cochrane review reported that opioids only have short-term effectiveness on chronic LBP, and approximately 50% of patients taking opioids long-term did not report an improvement in chronic LBP [7]. us, opioids only have modest effects on pain in patients with chronic LBP and no functional benefits; furthermore, approximately 50% of patients do not tolerate opioids [8].
Nonpharmacological treatments and alternative intervention may be more effective than pharmacological interventions in the management of chronic nonspecific LBP [2]. e guideline from the American College of Physicians and the American Pain Society recommends complementary and alternative interventions, such as exercise therapy, massage, or yoga, for the management of nonspecific LBP [9]. e systematic review of exercises used by LBP patients showed that a variety of exercises appeared to have beneficial effects for LBP and that exercise therapy for chronic LBP appears to be slightly effective in decreasing pain and improving function [10]. e therapeutic application of topical heat is used for the relief of musculoskeletal pain syndromes [11,12], and thermotherapy using mud can be also recommended to treat patients with chronic LBP [13], neck pain [14][15][16], or osteoarthritic pain [17]. An appropriate level of pain control by thermotherapy may be required before exercises for pain control in nonspecific LBP. Mud-heat therapy combined with exercise may be more effective for chronic nonspecific LBP relief than exercise only.
To date, no randomized clinical trial (RCT) has been specifically conducted to validate the efficacy of thermointervention using mud with core exercise in patients with nonspecific LBP; thus, the effects of mud-heat in this LBP population remain unclear.
e purpose of the present study is to investigate the effects of mud-heat intervention combined with core exercise on pain, functional disability by LBP, and static/dynamic balance in people with chronic LBP. We hypothesized that core exercise following pain control using mud-heat intervention would be more effective than core exercise only in people with chronic LBP.

Setting and Participants.
is study was conducted as a single-blind, randomized controlled trial and was approved by the Gachon University Institutional Review Board (1044396-201804-HR-105-01). e study was performed in accordance with the protocol, and all subjects provided written informed consent prior to their enrollment in the study. e inclusion criteria were adults with chronic, nonspecific LBP (pain severity (VAS) > 3/10) either with or without leg pain. Chronic LBP was defined when the duration of the current episode was ≥ 6 months. Participants were permitted to use over-the-counter medication as needed. e exclusion criteria were other concurrent provider-based treatments for LBP, contraindications to study treatment (e.g., clinical spinal instability and inflammatory arthropathies), benign joint hypermobility syndrome, and other serious physical or mental health conditions as determined by self-report, clinical examination, and history.

Experimental Procedures and Intervention.
All participants were randomly assigned to either the intervention group or the control group using a stratified randomization method [18]. e participants allocated to the intervention group received mud-heat intervention and then performed the core exercise applied in the previous study [19] for 50 minutes, twice a day, for 4 days, while the control group performed core exercise only.
To apply thermotherapy, moor mud was used in packs [14,17]; the moor mud was collected at the Chollipo Arboretum, Taean-gun, Chungcheongnam-do, Republic of Korea, in June 2018, and impurities were removed using a 5 mm and 90 μm sieve. Subsequently, 1.5 kg of the moor mud removed from impurities and 300 ml of deep sea water collected from Ulleungdo, East Sea of Korea, were mixed in a zipper bag (30 × 45 cm) and standardized to 1 cm in thickness. e pack was then enveloped by hemp cloth. e intervention group used a moor mud filled heat pad, whereby participants were instructed to heat the pad to a tolerable temperature and apply it on the lower back twice a day for 30 min over a period of 4 days.

Outcome Measures.
is study consisted of two primary (present pain intensity and pain pressure threshold) and three secondary (disability index, muscle properties, and static/dynamic balance) outcome measures.

Pain Intensity.
e 100 mm visual analogue scale was used to assess pain intensity at rest and during movement. e visual analogue scale at rest (resting pain) was defined as an unpleasant feeling or pain when patients were still. e visual analogue scale during movement (movement-induced pain) was defined as an unpleasant feeling or pain incurred by full flexion of the trunk [20]. Patients marked their subjective pain intensity at rest and during movement on a 100 mm visual analogue scale table.

Pain Pressure reshold.
e pain pressure threshold (PPT) was measured using a distal algometer (Somedic AB, Farsta, Sweden) with a 1 cm 2 probe in order to investigate changes in deep tissue nociception of the lower back muscles [21]. e pressure head of the algometer was applied to 5 points of the lumbar area [22]. To assess PPT, the PPT assessment method of a previous study was used [23]. e assessor increased gradually the pressure of the algometer to 10 kPa/s increments until the subjects expressed a pain response, such as a vocalization by pain and a gesture related to pain (hand grasp or eye blink). e mean threshold was calculated for the left-and right-side points.

Low Back Pain Disability.
e Oswestry Disability Index (ODI) was used to assess functional disability due to LBP; this consists of 10 items describing the impact of pain on different daily living activities [24]. In the current study, 9 of the 10 items were included, with the exception of sexual function. Each item is scaled on a six-point Likert scale (range 0-5), with 0 indicating no limitation due to pain and 5 indicating that an activity is impossible to perform. e total score ranges from 0 to 45, with a higher score indicating a higher level of disability. e ODI is the most widely used tool for assessing functional outcome in patients with LBP and is recommended for the evaluation of the effectiveness of LBP treatment [25,26].

Muscle Properties.
A handheld myotonometer (Myoton AS, Tallinn, Estonia) was used to measure the mechanical properties of muscle (muscle tone, stiffness, elasticity, relaxation, and creep) of the skeletal muscle at the same region that PPT was measured [27]. e measurements were made after placing the equipment perpendicular to the skin's surface and five repeated measurements were performed. e mean threshold was calculated for the left-and right-side points.

Static/Dynamic Balance.
is study used the force plate (Zebris Medical GmbH, Isny, Germany) to measure the center of pressure to analyze the static balance, and MR3 (ver. 8.6) was used to process signals [28]. e patients were placed on a force plate with bare feet. Subjects were kept in an upright posture and their hands were crossed with their arms in a narrow stand position (with ankle and toe touching) in either an eye-open or an eye-closed condition; the measurements were performed three times with a rest interval of 1 minute. e center of pressure (COP) was measured for 40 seconds, and the data for 30 seconds were used, except those for 5 seconds after the start and 5 seconds before the end.
e Timed Up and Go test (TUG) was performed to test dynamic balance; this test requires the performance of sequential motor tasks including standing up, walking straight for 3 m, turning, walking back to the chair, and sitting down [29]. e score for this test was the time required to complete the test, which was measured using a stopwatch. e test was performed twice and the mean was used as a representative value.

Statistical Analysis.
Data analyses were performed using SPSS Statistics 21.0 (IBM-SPSS Inc., Chicago, IL). e statistician was blinded to group allocation for all analyses.
e Mann-Whitney U test and Fisher's exact test were performed in order to analyze the general characteristics between the two groups. e Wilcoxon signed-rank test was used to compare the changes before and after the intervention. e Mann-Whitney U test was used to compare the changes between the two groups. A p value of <0.05 was considered statistically significant.

Participants' Characteristics.
In total, 49 participants were assessed for eligibility and 17 individuals were excluded from participating; 11 did not meet the inclusion criteria and 6 declined to participate. Allocation resulted in baseline comparability between the two groups. In the control group, one declined to participate after allocation. A total of 31 patients completed the study. Figure 1 shows the selection of participants in this study.
ere were no significant differences between the moor therapy and core exercise group (intervention group) and the core exercise group (control group) in terms of the general characteristics of patients with chronic LBP (sex, age, height, weight, duration, and pain intensity) (Table 1). Additionally, there are no significant differences in the prevalues of the outcome variables assessed in this study between the two groups. Table 2, the intervention group had a significantly decreased pain intensity at rest (p � 0.001) and during movement (p � 0.001) before and after intervention. Core exercise significantly decreased the pain intensity at rest (p � 0.001) and during movement (p � 0.001). Interestingly, compared to core exercise, moor therapy combined with core exercise significantly improved the pain intensity at rest (p � 0.048).

Primary Outcome Measure. As shown in
With regard to PPT, both groups had significantly increased PPT after intervention (intervention group: L1-M, Compared to core exercise only, moor therapy combined with core exercise led to a significant improvement in PPT (L3-M, p � 0.009; L5-M, p � 0.011).
As shown in Table 4, the intervention group showed with core exercise significantly improved the dynamic balance assessed by TUG than core exercise only (p � 0.019).

Discussion
To the best of our knowledge, this is the first investigation to demonstrate that 8 sessions of mud-heat intervention and core exercise provide benefits that are superior to core exercise only with regard to pain intensity, PPT, disability as a result of LBP, and static/dynamic balance in individuals with chronic LBP. More importantly, the reduction in pain observed with mud therapy combined with core exercise was not only statistically but also clinically meaningful. No significant group effects on muscle properties were documented for mud-heat therapy combined with core exercise vs. core exercise alone. ese results may provide evidence to use mud-heat therapy and exercise as an alternative intervention for pain relief and motor improvement in chronic LBP patients.
Medication is the first option in the relief of LBP, but long-term use of medications has side effects such as tolerance or hyperalgesia [7,8]. Furthermore, the use of medication for pain control can increase the risk of problems such as falls, fractures, and depression [30]. Given these drawbacks, nonpharmacological treatments can be considered as complementary and alternative interventions for the management of chronic nonspecific LBP. An appropriate nonpharmacologic pain control method, and improvement of back muscle strength and stability by core exercise, can be an option for the relief of LBP. e present study showed the effect of mud-heat intervention combined with core exercise for chronic LBP management as a nonpharmacologic and alternative intervention.
Interestingly, this study showed that mud-heat intervention combined with core exercise led to a significant improvement in pain at rest and PPT of low back compared to core exercise alone. In addition, the intervention group was statistically superior to the control group in terms of personal care, lifting, and walking with decreased pain. Previous studies that demonstrated positive effects of mud intervention on chronic musculoskeletal pain, including LBP, support our results [13][14][15][16][17]. e results of our study showed the feasibility of the clinical use of mud-heat intervention for the management of chronic nonspecific LBP. Furthermore, the core exercise alone group also demonstrated a reduction in pain, PPT, and LBP-related disability. Indeed, several studies that investigated the effect of core exercise on pain and sensory and motor function support our results [19,31,32]. Core exercise may influence the β-endorphin level in patients with chronic nonspecific LBP, and the mechanism of action of the pain-relieving effect of core exercise might be related to an endogenous opioid mechanism [32].
is study also examined the changes in muscle properties of the low back in both groups [33]. Both the intervention and control groups demonstrated significantly decreased muscle tone and stiffness, but elasticity, relaxation, and creep were not significantly different after the intervention. Compared to the core exercise group, the intervention group did not show significant differences in all muscle properties; thus, 8 sessions may not be sufficient to compare the muscle properties between groups. erefore, long-term and repeated interventions are needed in order to fully determine any changes in muscle tone.
Previous studies have reported that core exercise significantly increased proprioception in LBP [19], and the core stability exercise group showed significant improvements in postural control, assessed by changes in load transfer patterns during [31]. Despite the effect of core exercise on postural control, in this study, mud-heat intervention with core exercise was statistically superior to core exercise in terms of static balance as assessed by COP length. In addition, the intervention group had significantly better dynamic balance than the control group. e significant Evidence-Based Complementary and Alternative Medicine decrease in pain in the intervention group may be associated with a significant increase of static/dynamic balance in LBP patients [19].

Study Limitations.
ere are some limitations of the present study. First, since 8 sessions were applied for 4 days, the effect of repeated mud-heat intervention with core exercise over a long-term period is necessary to investigate the clinical use of mud-heat intervention. Second, this pilot study showed significant effects on pain intensity, PPT, LBPrelated low back pain, and balance in individuals with chronic LBP; however, the small sample size may limit the generalization of these results.

Conclusion
e findings of the study demonstrated the efficacy of moor heat combined with core exercise as an alternative therapeutic intervention for pain, disability, and balance in patients with nonspecific LBP. ese results recommend the use of moor mud for functional management of LBP patients in the clinic. Since the effect of this intervention on muscle properties was inconclusive, in order to support moor therapy as an evidence-based alternative intervention for nonspecific LBP, further studies with a larger sample size and long-term application of moor are needed.

Abbreviations
LBP: Low back pain PPT: Pain pressure threshold L1-M: 2 cm lateral to the L1 spinous process L3-M: 2 cm lateral to the L3 spinous process L5-M: 2 cm lateral to the L5 spinous process L1-L: 5 cm lateral to the L1 spinous process L3-L: 5 cm lateral to the L1 spinous process COP: Center of pressure TUG: Timed Up and Go test.
Data Availability e data of this study are available from the corresponding author upon reasonable request.

Consent
A written informed consent was obtained from all participants.