THE EFFICACY OF MUSCLE ENERGY TECHNIQUE IN INDIVIDUALS WITH MECHANICAL NECK PAIN: A SYSTEMATIC REVIEW

Introduction: Mechanical neck pain is a condition that includes minor strain / sprain in the muscles, ligaments, or facet joint dysfunction. Objective: This systematic review is aimed to find out the effectiveness of the muscle energy technique in mechanical neck pain. Method: The systematic review access to journal databases such as: PubMed, PEDro, and the Cochrane Library. Results: Based on inclusion and exclusion criteria 5 articles were used in this systematic review. The application of the muscle energy techniques was applied ranging from 1 time to 4 weeks of intervention. From the 5 reviewed studies concluded that muscle energy technique was effective in improving neck motion and function in mechanical neck pain. Conclusion: Based on the results of systematic review it can be concluded that the application of MET improve neck movement through The International Classification of Functioning, Disability, and Health (ICF) criteria evaluated by pain score, pain threshold, range of motion, functional performance, and muscle thickness. The appropriate articles are still limited to 5 studies, but have good to strong qualities. In addition, the application of intervention does not have the same standard.


BACKGROUND
Neck is the most mobile region in human body. Indirect cervical biomechanical changes affect the structure of the cervical spine. It causes neck pain. 1 The incidence of neck pain is around 15%. Neck pain is the second most common disease after low back pain that occurs in general population and musculoskeletal practices. 2 Neck pain occurs in approximately 67% of adults aged around 20-69 years. 3 In Indonesia, the incidence of neck pain has increased. Approximately 16.6% of adults complain of cervical discomfort and 0.6% clinically manifesting into severe neck pain. The incidence of cervical neck pain increases with age and is more often experienced by women compared to men in a ratio of 1.67: 1. 4 Mechanical neck pain (MNP) can originate from lesions on the zygapophyseal joint (facet joint) or the condition of muscle spasm in the cervical region. The source of symptoms of mechanical neck pain originates in the cervical, particularly in the uncovertebral joint or zygapophyseal joint. It causes the limitation of range of motion in all directions of cervical region, especially in the movements of rotation, extension, and cervical lateral flexion. Pain followed by a minor positional fault in muscle guarding of the levator scapulae, cervical paravertebral, and upper trapezius is closely related to the limitation of the range of motion of the cervical joint in mechanical neck pain. 1 Muscle energy technique is a soft tissue mobilization technique that is applied by combining isometric contractions. The application of this method is intended to restore soft tissue structure to normal and provide indirect effect on the joint that is associated with a dysfunctional muscle and can be used to normalize joint mobility in dysfunctional soft tissue structures. 1 Several studies have proven that the application of MET can reduce pain, improve the range of motion, and reduce the degree of neck disability. 5,6,7,8,9 However, the recommendation of application method and dosage have not been widely discussed by some previous studies.

METHOD A. Search strategy
The systematic review access to journal databases such as: Physiotherapy Evidence Database (PEDro), MEDLINE via PubMed, and the Cochrane Controlled Trials Register in the Cochrane Library.

D. Study quality assessment
In assessing the quality of studies, reviewers use the Standard Quality Assessment Criteria for Evaluating Primary Research Paper from a Variety of Fields. This criterion consists of a 14-item assessment checklist in which points were awarded to each criterion (no=0, partial=1, and yes=2). This criterion is a validated standard. 10 Article quality assessment was assessed by dividing the total assessment score by 28 then categorized into: limited (<50%), adequate (50% -69%), good (70% -80%), or strong (score of>80%).
Studied with percentage scores under 50% were excluded from this review. 11

E. Data extraction
Data were extracted by summarizing data on description of participants, intervention, control/comparison, outcome measure, results, and quality rating of the study.

A. Study selection
The initial search in 3 databases found a total of 32 articles. Then the selection using inclusion and exclusion criteria obtained 10 articles. The same article was then excluded. The total articles used in this study amounted to 5 articles. Explanation regarding study selection, described in Figure  1.

B. Methodological quality and risk of bias of reviewed studies
After assessing the quality of the study, there is no article was excluded because they had a score of <50%. The articles obtained have a strong category for 3 and good for 2 studies. Explanation regarding the quality assessment of journals, described in table 1.

DISCUSSION
The application of the muscle energy techniques was applied ranging from 1 time to 4 weeks of intervention. From the 5 reviewed articles concluded that muscle energy technique was effective in improving neck motion and function in mechanical neck pain. Evaluated measurements included: pain, range of motion, neck disability, and the thickness of the upper trapezius muscle. Table 3 describes the outcome measure used in this study to evaluate the limitations of body function and movement in mechanical neck pain based on The International Classification of Functioning, Disability and Health (ICF) criteria. MNP originates from lesions on the zygapophyseal joint (facet joint) or the condition of muscle spasm in the cervical region. MET is effective in increasing the range of motion due to the presence of post isometric relaxation (PIR) and RI (reciprocal inhibition) mechanisms. 12 PIR refers to the assumed effect of reduced muscle tone after isometric contraction. Hypertonia muscle will be stretched of the new range of motion. The therapist give the resistance from the opposite direction and the patient is asked to do isometric contractions by resisting the therapist's force for 5-10 seconds. After isometric contractions, the muscles will be stretched gently to increase muscle flexibility to the new range of motion. This procedure could be repeated 2 or 3 times. 12 In contrast to PIR, RI involves the physiological response of the antagonistic muscle that has been contracted isometrically. When muscles are contracted isometrically, the antagonist muscles will be blocked, and experience a decrease in muscle tone. The application of RI is done by utilizing antagonist muscle contractions. Muscles that experience lesions are positioned in the middle of the total degree of range of motion. The patient is asked to contract in a limited direction while the therapist gives resistance in the opposite direction (isometric) or even allows movement toward it (isotonic). This is followed by relaxation of the patient and also exhalation. At the same time, therapists passively stretch the muscle in a limited direction with new range of motion. This procedure is repeated 3-5 times. 12 Based on the systematic review, it was found that the application of MET on mechanical neck pain can reduce pain evaluated through visual analogue scale. Fryer and Fossum at (Nagrale, et al., 2010) stated that the sequence of muscle and joint mechanoreceptor activation stimulates the local somatic efferents. It turn leads to sympatho-excitation and activation of the periaqueductal gray matter, which play role in the descending modulation of pain. 5 Frontera at (Phadke, et al., 2016) stated that the reduction in pain could be due to the inhibitory effects of golgi tendon organs (GTO), which reduces the motor neuron discharges. It is causing relaxation of the musculotendinous unit by resetting its resting length and pacinian corpuscle modification.
These reflexes allow relaxation in musculotendinous and decreased pain perception. 7 In other words (Sadria, et al., 2017) summarize that the application of MET could stretch and increase the myofascial tissue extensibility and affect the viscoelastic tissue properties and mediate the changes of extracellular fluid dynamics and fibroblast mechano-transduction. 8 Because of this mechanism, there is also an improvement of the range of motion and a reduction of the muscle spasm. Therefore, there is improvement in neck disability. 5,6,7,8,9

CONCLUSION
It can be concluded that the application of MET improve neck movement through The International Classification of Functioning, Disability, and Health (ICF) criteria evaluated by pain score, pain threshold, range of motion, functional performance, and muscle thickness.

RESEARCH LIMITATIONS
The appropriate articles are still limited to 5 studies, but have good to strong qualities. In addition, the application of intervention does not have the same standard.