The effect of muscles energy technique in the management of chronic mechanical low back pain: A scoping review

2.1Study design

The concept of this scoping review is based on the recommendation from the work of Arksey and O’Malley [27], which was further developed by Levac and co-workers [28]. The methodological framework of Arksey and O’Malley [27] proposes five stages that include: identifying the research question, identifying relevant studies, study selection, charting the data and collating, and summarizing and reporting the result of the study.

The first stage is to identify gaps in the empirical evidence on the effectiveness of MET in the management of chronic MLBP and the final stage is to conclude from the existing literature with regard to the overall state of studies on MET. The scoping review methodology will capture a range of studies on the topic with the purpose of summarizing (knowledge syntheses) the existing literature for the benefit of researchers and clinicians. This type of review does not focus on assessing the quality of the studies, rather the aim is to capture a broader range of literature, including all types of study designs [27].

2.2Research question

To ensure that a broad range of relevant literature is identified, the following research question was set: “What are the treatment effects of MET on pain, bodily structures and functions, quality of life, and activities of daily living in the management of chronic MLBP?” In determining the question, we acknowledge the recommendation to maintain a wide approach in defining the parameters at this stage of the study to generate a wide breadth of coverage [27, 29].

2.3Search strategy

The electronic databases Cochrane Library, PubMed, Europe PMC, PEDro, Google Scholar, ScienceDirect, WorldCat, Osteopathic Medicine Digital Repository (OSTMED-DR), EBSCOhost, Osteopathic Research Web and ClinicalTrials.gov were screened to retrieve the available evidence regarding this topic from 2003 to 2019. To identify relevant studies an electronic search was performed in these databases using the combination of the following keywords and/or their synonyms: (“muscle energy technique” OR “MET” OR “manual therapy”) AND (“mechanical low back pain” OR “non-specific low back pain”) AND (“management” OR “treatment of low back pain”). Eligibility assessment of the retrieved articles was performed by screening them against the predefined inclusion and exclusion criteria as outlined in Table 1. In short, all English full-text reports of original studies examining the intervention effects of MET (as a standalone or combined treatment) delivered by a physiotherapist, osteopathic physician or chiropractor for the management of chronic MLBP in an adult patient population were eligible for study inclusion. To search as complete as possible, a hand search was performed entailing that reference lists and citations of the included studies retrieved from the electronic search were screened to identify additional relevant studies. In case such studies were retrieved they were screened for the fulfilment of the inclusion criteria.

Figure 1.

Article selection process.

2.4Study selection

The process of article selection includes four steps: identification of relevant literature, screening of the title and abstract against inclusion and exclusion criteria (Table 1), assessing eligibility based on full-text screening to the in/exclusion criteria, and final inclusion of the article for the review [27, 28]. The number of records retrieved and included in each of these steps is depicted in Fig. 1. The electronic search was performed by the first author UAA. UAA and SSM screened the retrieved articles against the inclusion and exclusion criteria, first based on title and abstract, second based on the full text. The hand search existing of reference list screening was performed by UAA, and the screening of the resulting articles for study eligibility by title and abstract and subsequently full text was performed by UAA and SSM. Two experts in manual therapy and musculoskeletal research provided their expert opinion on the recommendations for appropriate electronic databases and relevance of any article that the reviewers disputed on with regards to the inclusion.

2.5Charting the data

A data charting form was developed as recommended by the work of Arksey and O’Malley [27] and used to extract and summarize the data from individual articles included in this scoping review. The data extracted includes general information about the article (title, author(s), journal and year of publication), and information on the study design, study setting, participants characteristics and methodology. Also, a summary of the main results, limitations and recommendations are presented in the data charting form.

2.6Summarizing and reporting findings

Arksey and O’Malley [27] describe the final stage of scoping reviews to provide an overview of the results of the reviewed articles, in this case, the reportage focuses on the results of the studies in regards to the effectiveness of MET in the management of chronic MLBP.

3.1Population

The systematic search strategy as demonstrated in Fig. 1 yielded eleven articles which were considered eligible for this review [30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40]. Table 2 illustrates the details of the eleven articles used for the final analysis and discussion. All the studies were carried out in an urban setting, although in three studies the authors did not specify the location of the study [30, 31, 32]. Among the selected studies two studies were carried out in North Africa [30, 31], three were conducted in India [33, 34, 35], two in North America [36, 37], one in South America [38], and two in Europe [39, 40]. The study by Lamberth et al. [32] did not disclose in which geographic region the study was carried out, however, all authors are from Denmark and therefore we presume the study was conducted in Europe. Ten of the eleven studies performed a randomized controlled trial (RCT), while only one study used a case design [32]. Both male and female adult participants with chronic MLBP were recruited for all the studies and with age ranges of 20–60 years.

3.2Interventions

In all the selected studies, the effectiveness of MET was tested as outlined in Tables 2 and 3. However, in two of the studies [36, 37], the name MET was not used, rather the terms used were ‘manual therapy’ and ‘regional manual therapy’ respectively. In ten out of the eleven studies the interventions were administered by a physical therapist, and in one study [32] by a medical doctor with a diploma in musculoskeletal medicine. In four studies [35, 36, 37, 39] the interventions were exclusively conducted by physical therapists specialized in musculoskeletal therapy and many years of experience in the practice. Additionally, seven of the nine studies were conducted in hospital located in urban settings where patients were also recruited for study participation (Table 2). The study by Geisser and et al. [36] was carried out in a university spine laboratory on chronic MLBP patients. The studies by Ellythy [30, 31] and Rana et al. [35], did not specify the type of location (i.e. whether urban or rural) of the studies settings. The participants received multiple sessions of interventions ranging from 5 to 24 sessions, conducted within a span of 1 to 8 weeks. All studies aimed to determine the effectiveness of MET or its combination with other therapeutic interventions in the management of chronic MLBP. The other interventions MET was combined with included McKenzie method therapy, specific motor control exercises, conventional therapy, and G.D. Maitland’s concept of mobilization, myofascial release and segmental stabilization.

In the study by Szulc et al. [40] McKenzie techniques that involve hyperextension techniques, hyperextension with self-pressure or pressure applied by the therapist and hyper-extensive mobilization were used. The sagittal plane was used to apply the techniques following the rule of force progression. This procedure was applied isolated in one group and in-combination with MET in another group. The MET is a technique of post-isomeric relaxation at the end of each McKenzie session and involved the following parameters: 1) time of contraction equal to 7–10 seconds, 2) intensity of contraction corresponding to 20–35%, 3) 3 seconds of an interval between consecutive contraction phases, 4) 3 repetitions, 5) contraction of antagonist’s muscle at the terminal phase of the procedure, 6) passive return to the baseline position. This procedure is aimed at relaxing the erector spinae muscle group and was performed in a sitting position for 40 seconds. The third group of participants received standard physiotherapy treatment that involved massage,   laser therapy,  and transcutaneous electrical

nerve stimulation (TENS) applied to the lumbosacral region. Additionally, the participants were asked to perform general exercises for strengthening spinal and abdominal muscles at home.

The study by Balthazard et al. [39] combined MET with active exercises in group A and compared it with placebo therapy combined with active exercises in group B. The MET intervention involves a hold-relaxed technique performed on an ilium dysfunction with the participant in side-lying, high velocity, and low amplitude dynamic thrust (manipulation), a rotational-lateral flexion thrust performed on a stiffed vertebral segment with the participant in side-lying. Another mobilization technique was added that involves passive accessory intervertebral movements, a central or unilateral posterior-anterior pressure applied on painful or stiffed vertebral segment(s) with the participant lying prone [39]. The sham treatment involves detuned ultrasound applied to the patient’s painful and/or inflammatory site. The participant did not know the ultrasound was inactivated and, therefore, ineffective. The active exercises in both groups involved; 1) mobility exercises throughout the eight therapeutic sessions to improve participant’s spinal range of motion and pain, 2) passive stretching exercises after the second session, for muscle groups that tend to shorten (erector spinae, hamstring, iliopsoas, rectus femoris, piriformis), to relieve muscular tension and improve low back mobility, 3) motor control exercises at the fourth session for active recruitment of stabilizing trunk muscles, 4) strengthening exercises at the sixth or seventh session to increase the strength of weak superficial trunk muscles. They were performed at 60–70% of maximum voluntary contraction, against the resistance of an adapted rubber band, 2 sets of 20 repetitions, 5) two home mobility exercises (pelvic tilt and low back lateral flexion, in supine), to be performed daily, twice a day, 2 sets of 10 repetitions. After the third or fourth therapeutic session, the recommendation of home exercises changed to stretching and motor control exercises. The therapeutic sessions lasted for thirty 30 minutes in each group and consisted of 5 to 10 minutes of MET/Manual therapy intervention followed by an active exercise for group A and 5 to 10 minutes of ST intervention followed by an active exercise for group B.

Geisser et al. [36] compared MET, sham MET, a specific adjuvant exercise program and a non-specific exercise program. The principal mechanism of the MET procedure was similar to the one used by Szulc et al. [40]. The sham MET involved controlled corrective positioning of the participants, and specific adjuvant exercises aimed at treating specific musculoskeletal dysfunction including stretching, strengthening and self-correction exercises, while the non-specific exercise program, which included aerobics and lower limb stretching exercises, did not target any observed dysfunctions of the lumbar musculoskeletal system.

Bindra compared MET to conventional therapy [34]. The MET protocol was similar to the previous studies but in this study, the parameters varied depending on the level of dysfunction observed during participant screening. The conventional therapy group included therapeutic ultrasound, TENS and mobility exercises (i.e. knee to chest exercise and pelvic rotation to either side with a hold of 10 seconds in each position and 8–10 repetitions were performed).

Dhinkaran et al. [33] also compared MET to conventional therapy, the latter comprising of TENS. However, both intervention groups also received corrective exercises for which participants were asked to flex the hip and bring the knee into the ipsilateral axilla from a supine, sitting or standing position.

Rana et al. [35] compared MET to Maitland’s concept of mobilization and added therapeutic exercises to each intervention. In their study, the MET application was dependent on the extent of the presented dysfunctions established during an assessment.

Ellythy conducted two different studies [30, 31]to determine the efficacy of MET compared to other therapeutic interventions. The first study compared MET (group A) versus strain counter strain technique (group B) which is described by the author as another indirect manipulative procedure [30]. Also, both groups of participants received standard physiotherapy treatment that involved infrared radiation, ultrasound therapy, and therapeutic exercises (i.e. finger to toe flexion, bridging exercise, back extension in prone, sit-ups, knee to the chest in supine and stretching of low back muscles). The second study compared MET with a myofascial release which is directed toward the soft tissues of the body, particularly the muscles and fascia [31]. In this study also a standard physiotherapy procedure was added to both groups, which involved infrared radiation, TENS, ultrasound therapy, and therapeutic exercises (i.e. finger to toes, bridging, back extension in prone, sit-ups, knee to chest and stretching back muscles).

A modified form of MET in the form of muscle stretching was compared with segmental stabilization exercises in a study by Franca et al. [38] aimed to restore motor control of the deep trunk muscles (specifically transverse abdominus (TrA) and lumbar multifidus muscles (LM). Emphasis was placed on the pattern of activation of the TrA in individuals with chronic MLBP.

The only pilot study among the included studies comprised of a multi single-case study aimed at assessing the short and long-term effects of MET in patients with chronic MLBP [32]. The type of MET procedure used in this study is attributed to Fred L. Mitchell Sr [25].

Zafereo et al. [37] administered regional manual therapy to patients with chronic MLBP. Although the procedure is not entirely MET, the concept was to apply different manual therapy techniques. The choice of initiating, grading or suspending any specific technique and duration of treatment was left to the discretion of the treating therapist. The protocol was compared with standard physiotherapy, and motor control exercises were added to both interventions.

3.3Outcomes

The main outcomes of interest were pain intensity, functional disability, and trunk range of motion (ROM). Pain and disability-related outcomes were measured using self-reported clinical outcome measures that included visual analogue scales, numeric pain rating scales, or validated questionnaires like the Oswestry Disability Index (ODI) or Quebec Back Pain Disability Scale (QBPDS). To measures trunk ROM, different measurement tools and procedures were used such as electrogoniometres, inclinometers, measuring tape and performance of the modified-modified Schober test. Besides, one study used a pressure biofeedback unit to assess the activation/contraction rate of the TrA muscles to evaluate treatment effects on motor control [38]. Another study used the Sorensen test to assess the endurance of the erector spinae muscles and the Shirado test to assess the endurance of the abdominal muscles [39]. Furthermore, the structure of the spinal discs was assessed using magnetic resonance imaging (MRI) in one of the studies [40].

Generally, MET was found to be effective in improving the outcomes in patients with chronic MLBP in all included studies. Some of these studies found that adding additional exercises to MET was more effective than MET alone. None of the studies showed any adverse effect on the application of MET intervention alone or in combination with other therapeutic procedures, as none of the outcome variables showed diminishment. However, a couple of studies have reported that the MET in combination with other treatment interventions did not provide better effects in comparison to the other interventions on some outcome variables. Geisser et al. [36] reported that MET plus specific exercises of the trunk muscles was effective in reducing pain, but there was no significant change in functional disability. However, the authors argued that it is possible that reducing solely the LBP complaints does not address psychosocial or other factors that may contribute to disability. Franca et al. [38] reported that although MET (in the form of muscle stretching) is effective in improving outcomes (i.e. pain, ROM, functional disability and spinal disc structure) in patients with chronic MLBP, segmental stabilization exercises provide even better results and additionally improved motor control as reflected by the activation of the TrA which was not the case for MET. Also, the study by Balthazard et al. [39] reported a pronounced decline in abdominal muscle endurance in participants treated with MET and active exercise compared to participants treated with sham therapy and active exercise, however, a clear explanation for this observation could not be given and thus further studies were recommended to enhance the understanding of the relationship between MET, active exercise and abdominal muscles endurance. However, the latter study did confirm the immediate analgesic effect of MET in patients’ chronic MLBP.

4.1Implications to research and practice

The findings of this study provide information which can be used to help steer the development of an effective treatment protocol for MET for the rehabilitation of patients with chronic MLBP by reducing the rate of recurrence, prevent structural and functional alterations and improve functional disabilities. Studies on the effectiveness of MET in populations from the middle to low-income countries and/or rural areas are limited and therefore the effectiveness of and feasibility to implement this intervention has not yet been well researched globally. We hope that this study will stimulate interest in further research involving MET in the management of chronic MLBP among the general and specific populations, because of the dearth of studies on the subject. Consequently, it is recommended that further studies focus on examining the efficacy of the intervention using a robust methodology including a clear description of the setting where subjects were recruited and treated, the used techniques and related decision making, therapist experience, and a long term follow-up.

Additionally, this review will help clinicians to understand the clinical importance of application of MET in combination with other therapeutic procedures as an appropriate management plan for chronic MLBP, which will improve patients’ functional disabilities. This review serves as a resource material, reference or guide that researchers and clinicians can consult to obtain useful information about MET in the rehabilitation of chronic MLBP and potentially other related musculoskeletal conditions.

An additional remark is that we have noticed that MET is not included in many clinical practice guidelines for the management of MLBP, while the finding of this study reveals MET studies with encouraging outcomes. Therefore, we recommend that the MET procedure needs to be included in future clinical practice guidelines for the management of chronic MLBP.

Finally, with the increase in the prevalence of chronic MLBP, there is a need for funding agencies to support research that explores and analyses interventions for the management of this condition as MET offers a cheap and easy to apply intervention for this population. This is highly recommended especially for the benefit of patients from low and middle-income countries.

4.2Limitations

First, a limitation of this review was the inclusion of studies that are not RCTs of which one was a case study design while another was a pilot study. However, following the scoping review method, it is valid to include studies with designs of lesser quality and a range of different methodologies to entirely chart the available evidence related to the research question and broadening the level of evidence for analysis and discussion.

Second, this review included only articles written in English and published in peer review journals. This might have limited the evidence by not including articles written in other languages that may have been eligible for inclusion to this review. However, this criterion was adopted to avoid errors that may occur in representing accurately evidence reported in articles published in languages other than English.

Finally, two studies included for the review analysis used muscular stretching and regional manual therapy instead of MET as their manual therapy intervention [37, 38], however, a thorough expert review of both procedures indicated that this technique while not being labelled in the papers as MET could indeed be considered as meeting the principles of MET.