1. Introduction
Low back pain (LBP) represents a main reason for physician visits, hospitalization, or seeking other health care services [
1]. In literature, the lifetime prevalence for LBP varies between 51–84%. LBP is not only common, but also holds a significant cost and health care utilization burden, as it is a leading cause of disability [
2].
Chronic LBP is defined as back pain that persists for three or more months. In addition to persistent pain, many individuals often report sleep disturbances, depression, and high levels of fatigue [
3,
4]. The underlying cause is often not easy to detect, often because mismatches between symptoms and diagnostic results (both clinical examination and imaging) is common [
5]. Therefore, the optimal treatment choice is still challenging. However, in chronic back pain patients, a multidisciplinary approach combining medical, psychological, physical, and interventional therapies appear to be the most effective treatment, considering individual patient characteristics [
6,
7,
8].
Pharmacologic treatments are common but associated with side effects and risk of medication abuse; for this reason, nonpharmacologic interventions are important in helping to reduce symptoms and disability [
9]. Current evidence-based clinical guidelines propose exercise therapy as one of the few recommended treatments for chronic LBP [
10].
Unfortunately, there is no evidence showing that one form of exercise is better than another; guidelines usually recommend exercise programs based on individual needs and capabilities. Regardless, the response to such treatment is not satisfactory in many patients, with only modest changes in pain and disability [
10]. Even if the reasons for the widely varying individual response are largely unknown, one factor influencing individual success may be the adherence of the patient to the treatment.
As conventional treatments often show only modest clinical effects, over the last years the utilization of alternative pain management methods is rising [
11]. A subgroup of these therapies, the so called reflex therapies, acts mainly on the basis of reflex pathways via the spinal cord [
12].
Among them, acupressure is a noninvasive, low-cost technique which was established and used in Traditional Chinese Medicine and makes use of physical pressure on specific points using a finger or a device [
13]. Systematic reviews on acupressure support significant effects on chronic symptoms, such as pain and sleep disturbance [
14]. Acupressure was also reported to positively modulate objective physiologic pain markers, such as proinflammatory and anti-inflammatory cytokines and neuropeptides [
15]. A systematic review also demonstrated that the efficacy of treatment did not differ whether the acupressure was given by a therapist or self-administered, supporting its ease of use and low-cost [
16]. Basing on acupressure principles, some authors proposed the use of a needle stimulation pad for patients with neck or back pain, but also for other conditions, such as headache, sleeping disorders, gastrointestinal diseases, or just for relaxation [
17,
18]. This device is usually composed of sharp but nonpenetrating plastic needles and the patient lies on it with the painful part of the body. The precise mechanism of action of a needle stimulation mat is not clear but probably depends on different aspects.
Mechanical skin stimulation increases local blood microcirculation and tissue metabolism processes by actively supplying oxygen and removing carbon dioxide, thus reducing the concentrations of inflammatory cytokines [
19]. The mechanical stimulation of skin, subcutaneous tissue, and muscles is similar to that obtained with other complementary and alternative medicine manual and physical therapies (for example, gua sha massage and wet cupping). Such stimulation likely activates skin mechanoreceptors and even nociceptors, thus affecting the transmission and processing of sensory information to a spinal and supraspinal level [
12].
Therefore, the use of a needle stimulation mat can influence pain chronicity mechanisms, that may originate at the level of the nociceptor, the spinal cord, or the brain, even when the initial injury or inflammation is no longer present [
20]. Indeed, a widespread sensory hypersensitivity could be linked to central hypersensitivity, augmented central pain processing, or decreased descending pain control [
21].
The purpose of this randomized controlled trial was to evaluate the therapeutic efficacy on pain and disability of a new acupressure mat device associated with a specific rehabilitation program in patients with nonspecific chronic low back pain.
4. Discussion
The objective of the present study was to evaluate the therapeutic efficacy of an acupressure mat (Mysa®) associated with a specific rehabilitation program in patients with nonspecific chronic low back pain.
Our results suggest that the rehabilitative protocol proposed to all the participants gave a significant positive effect in terms of reducing pain and disability, especially immediately after the end of the supervised sessions, while a significant improvement in life quality was found only in the experimental group.
Based on the most recent recommendations, the rehabilitative approach we proposed also included patient education about the pathogenesis of pain and about the rules of postural and behavioral hygiene. Indeed, as stated by different international guidelines, individuals with chronic LBP usually need to be provided with advice and education about the nature of low back pain to minimize disability and promote participation in physical and social activities [
28,
29]. Education is an easily available and inexpensive treatment option that explains to subjects how to protect their back in activities of daily living based on anatomical, physiological and ergonomic principles (the biomedical model). It also involves pain biology education, or “explaining pain”, that aims to reconsider pain as a protective output of the brain rather than a simple sign of tissue damage [
30,
31].
According to current evidence-based clinical guidelines, exercise therapy (of any type) is one of the few recommended treatments for chronic LBP and typically includes a graded activity or exercise program that targets improvements in function and prevention of worsening disability [
10]. Indeed, many studies showed that exercise training is effective in reducing pain when compared to that of non-exercise, training-based treatments in adults [
32]. Since there is no evidence showing that one form of exercise is better than another, guidelines typically recommend exercise programs that take individual needs and characteristics, preferences, and capabilities into account in deciding what type of exercise [
7,
33]. However, some works support the efficacy of resistance and stabilization/motor control exercise training and state that stretching exercises are most associated with pain reduction, while strengthening yields greatest functional gains [
34]. In a recent review of Owen et al., exercise training was demonstrated to be more effective than hands-on therapist treatments [
35].
The exercise protocol proposed in this work was directed by an expert physiotherapist. Basing on the previous literature, patients firstly underwent a clinical assessment to determine eventual signs of segmental hypo mobility or hypermobility and the progression of the exercises was directed accordingly [
36]. In addition to spine mobilization exercises, the therapeutic program included muscle strengthening and stretching, motor control, and breathing exercises; they consisted of mainly open chain ground exercises, and some of them included the use of a fit ball. As Hodges and Richardson demonstrated that an alteration in the timing of core muscle activation in subjects with LBP, particular attention was placed on core stability exercises [
37]. Considering the chronicity of pain and disability, the therapeutic intervention also involved the education of the patients to repeat the exercises learned in a home setting, with the aim of improving and maintaining over time the effects of the supervised rehabilitative program. The patients were provided illustrated brochures describing the exercises, their purpose and how to incorporate them into their activities of daily living. Moreover, an important factor that influences the individual success of exercise rehabilitation is represented by the patient’s adherence to the proposed treatment. In a prospective study, Mannion et al. demonstrated that the adherence to exercises has a positive correlation with the reduction of pain and disability [
38]. In our trial, all patients completed all the physiotherapy sessions, and this could explain the positive results obtained by both the treatment groups. While in the short term both groups exhibited significant improvements in terms of pain relief and reduced disability, after the conclusion of the supervised rehabilitative treatment only the experimental group showed a trend of further improvement. Such better results, especially at the 6-months follow-up, are likely attributable to two aspects: first, therapeutic exercises are likely to be performed more correctly when they are supervised by a qualified therapist; second, the home use of the acupressure mat is simple and seems to give additional long-term benefits. The first aspect agrees with what Matarán–Peñarrocha et al. demonstrated in a recent study in which they compared the effectiveness of a supervised physical therapy program versus a non-supervised one on pain, functionality, fear of movement, and quality of life in patients with nonspecific chronic low back pain. Despite small differences, the patients who received supervised exercise showed more improvement in both the short and long term over the non-supervised group [
39]. Similarly, in a previous randomized control trial, Bronfort et al. obtained better clinical results with supervised exercise rather than chiropractic spinal manipulation and home exercise in the treatment of chronic LBP, even if also in this case the differences between groups were small [
40]. Regarding the second aspect, all the patients allocated in the experimental group referred to continue using the mat every day for 60 min until the final follow-up evaluation, as recommended.
Even if the precise mechanisms of action remain unclear, the long-term benefits related to the use of the acupressure mat were investigated in previous clinical studies and are likely attributable to several aspects, including increased local blood microcirculation and tissue metabolism processes, activation of skin mechanoreceptors, and changes in pain processing [
12]. In two prospective randomized trials, Hohmann et al. investigated the effects of a two-week treatment period with a mechanical stimulation pad in patients with chronic neck or low back pain. They reported a significant pain reduction accompanied by an increase of pain pressure threshold, thus assuming that the treatment effect could be due to changes of nociceptive processing in the spinothalamic tract as well as at the level of the central nervous system [
17]. In another study, Kjellgren et al. analyzed the effects of a 15 min daily rest during three weeks on a spike mat in patients with neck or low back pain. A significant reduction in experienced pain intensity and little effects in increasing optimism and energy were found. For these authors, a possible explanation of these beneficial effects could be related to the local increase in blood flow and to the gate-control theory [
41]. In a randomized controlled trial, Purepong et al. investigated the effect of an acupressure backrest on pain and disability in office workers with chronic nonspecific LBP. The acupressure backrest was installed onto the office chairs of participants for one month and showed a beneficial effect on pain and disability that was maintained also at a 3-months follow-up [
42]. As highlighted by Zilberter and Roman, another possible mechanism of action attributable to the acupressure mat is related to the release of endorphins into the blood stream. Indeed, different kinds of skin stimulation were demonstrated to trigger the release of these mediators that exert an endogenous stress- and pain-protective action [
43]. Olsson et al. demonstrated that the use of a mechanical stimulation mat has substantial effects on the autonomous nervous system, inducing self-rated relaxation, increased back temperature, variation in blood pressure, and heart rate [
17]. The reported deep relaxation contributes to well-being, and thus works through the affective-motivational component of pain [
44].
In accordance to this evidence, all patients in the experimental group (EG) in our study reported a subjective feeling of general relaxation as they lay on the mat. Notably, during chronic back pain there is an alteration of back and neck sensory information, as demonstrated by Moseley and coworkers [
45,
46], that leads to altered back and trunk sensory perception [
47]; for this reason, a perceptive rehabilitation based on training with specific surfaces can be effective in reducing pain in patients with chronic low back pain [
48]. No significant adverse effects were reported in the present study. Therefore, the acupressure mat (Mysa
®) can be considered a safe device, according to previous studies which highlighted only a temporary discomfort or pain experienced during the relaxation on the spike mat that decreased over time. These properties of tolerability and safety, together with the possibility of using it autonomously at home, make the acupressure mat (Mysa
®) a valid tool for the long-term management of subjects suffering from chronic low back pain. This study has some limitations: the sample size was relatively small, and the follow-up period was relatively short, especially if related to the typical long-term chronic course of the disease in question. Another significant limitation was the lack of a “sham” acupressure procedure that could reduce the possible influence of placebo effect and psychological factors, especially in pain perception mechanisms. Furthermore, we did not use specific instruments to monitor the home use of the mat and adherence to home exercises; we instead relied on what the patients reported, that is, a high adherence to the use of the mat. For all these reasons, randomized controlled trials with longer follow-up periods and precise monitoring of mat use and adherence to home exercises are needed to further confirm our findings.
