Continuing Education Activity

Post-isometric relaxation is the most commonly used muscle energy technique (MET) in osteopathic medicine for improving thoracic spine restriction. MET is used by osteopathic physicians as a conservative, nonpharmacological treatment method for somatic dysfunctions of the musculoskeletal system. MET is a form of manual therapy and stretching. The patient actively contracts muscles in a precise direction while the therapist provides counterforce resistance. Isometric contractions relax and lengthen muscles. This activity discusses the procedural method for using MET with post-isometric relaxation to treat the thoracic spine's somatic dysfunction, the relevant anatomy and physiology, and its indications and contraindications. 

Objectives:

• Screen patients effectively to assess their suitability for muscle energy technique with post-isometric relaxation, considering factors such as acute fractures, dislocations, tissue damage, and central muscle spasm.

• Differentiate among somatic dysfunctions and other underlying disease processes such as infection, fracture, or malignancy that require alternative management approaches.

• Select the appropriate frequency, duration, and intensity of the post-isometric relaxation muscle energy technique sessions based on patient response and treatment goals.

• Communicate effectively with patients about the rationale, benefits, and potential risks of the muscle energy technique with post-isometric relaxation as part of their overall treatment plan.

Introduction

Muscle energy technique, commonly known as MET, is a form of manual therapy and stretching used in osteopathy. The patient actively contracts muscles in a precise direction while the therapist provides counterforce resistance. Isometric contractions relax and lengthen muscles. The technique is often regarded as direct, as the patient is placed toward the barrier.[1] 

In 1948, Fred Mitchell, Sr, DO, developed the technique after deducing the kinematic motions in the pelvis. From these concepts, he started to treat these somatic dysfunctions using muscle action as an activating force.[2] Osteopathic physicians typically use MET to correct somatic dysfunction that causes pain and discomfort, especially when performing therapy on the thoracic spine.[3][4]

There are 9 physiologic principles to muscle energy: joint mobilization using muscle force, respiratory assistance, oculocephalic reflex, reciprocal inhibition, crossed extensor reflex, isokinetic strengthening, isolytic lengthening, muscle force in one region of the body to achieve movement in another and post-isometric relaxation. Out of these 9, post-isometric relaxation is the most commonly performed MET. 

Dr Mitchell, Sr initially hypothesized that after an isometric contraction, the muscle is in a refractory state where it may be passively stretched without a reflexive contraction. MET with post-isometric relaxation involves putting increased tension on the muscle fibers by asking the patient to contract against a barrier; this activates the Golgi tendon fibers. Once activated, there is a reflexive inhibition and relaxation of the muscle through the Ia fibers, and the clinician may further passively stretch the muscle due to the refractory state.[2]

Anatomy and Physiology

A comprehensive understanding of muscle physiology is imperative for mastering MET. There are 4 types of muscle contraction: isometric, concentric, eccentric, and isolytic. Isometric contraction is when the muscles contract without having the origin and insertion of the muscle approach each other. Concentric contraction is when the muscles shorten with contraction. Eccentric contraction is when the muscle lengthens with contraction. And finally, isolytic contraction is when an external force lengthens muscle contraction.[5]

Muscles consist of numerous muscle spindles. Each spindle has approximately 3 to 12 intrafusal muscle fibers surrounded by a large extrafusal fiber. Each muscle spindle has an efferent and an afferent neural component. Motor nerve fibers are the alpha motor neurons innervating the extrafusal fibers and the gamma motor neurons innervating the intrafusal fibers. The afferent (sensory) portions are the Ia and II fibers that innervate muscle spindles and the Ib fingers, which innervate the Golgi tendon organs at the myotendinous junction.[6]

Golgi tendon fibers play a crucial role in MET through a post-isometric relaxation mechanism. The fibers are stimulated when muscles experience heightened tension, initiating a negative feedback loop that inhibits further contraction via the Ia fibers.[2]

The thoracic spine consists of 12 spinal vertebrae, and it holds particular significance for osteopathic physicians due to its association with sympathetic nerve fibers. Somatic dysfunctions in this region can result from biomechanical factors, such as restrictions in segments affected by surrounding muscles, or they may even have viscerosomatic origins. While the scope of this review does not cover viscerosomatic reflexes, addressing and understanding these issues is crucial for osteopathic care.

Thoracic vertebrae have a posterior spinous process, an anterior vertebral body, and bilateral transverse processes on each side. These vertebrae have facet joints above and below, facilitating articulation with adjacent segments. The superior facet joint in the thoracic segment is oriented in a posterior, upward, and lateral direction. Due to the presence of the ribs, thoracic vertebrae also have a superior and inferior costal facet near the vertebral body and a transverse costal facet on the transverse process. The orientation of T12's articular facet may face slightly from the other thoracic vertebrae due to its articulation with L1.[7]

The Rule of Threes, frequently taught in osteopathic education, aids in pinpointing the location of the spinous process concerning the transverse process. According to this rule, for T1 through T3, the spinous process aligns with the transverse process. For T4 through T6, the spinous process is positioned midway between the transverse processes of the adjacent segments. From T7 through T10, the spinous process is at the level of the next transverse process (the 7th spinous process is at the level of T8). The 11th spinous process is halfway, and the 12th spinous process is at the same level as its transverse process.[8][9] Debates over the accuracy of the Rule of Threes and the consideration of Geelhoed's rule are topics of discussion, but they fall outside the scope of this activity.[9]

Somatic dysfunctions are categorized into 2 types. Type 1 dysfunctions involve a group of segments and often result from chronic poor posture. These dysfunctions typically affect the larger, long-supportive muscles of the back, like the erector spinae, and are usually positioned neutrally but with rotation and side bending in opposite directions. On the other hand, Type 2 dysfunctions are often more acutely tender and affect the smaller supportive muscles between segments, such as the rotatores, multifidus, interspinales, and intertransversarii muscles. Type 2 dysfunctions are typically characterized by flexion or extension, side bending, and rotation in the same direction.[10][11]

Indications

MET with post-isometric relaxation is indicated in somatic dysfunction as long as there are no contraindications. If a muscle is painful, it may be a better candidate for MET with reciprocal inhibition. 

MET with post-isometric relaxation is indicated for the treatment of somatic dysfunction in the thoracic spine resulting in, but not limited to:

• Back pain [12]
• Decreased range of motion [13]
• Respiratory dysfunction

Contraindications

MET with post-isometric relaxation is contraindicated in patients with an acute fracture or dislocation. Those with tissue damage to ligaments, tendons, and muscles may not be the best candidates. It is best to wait for vital stability before trying this technique. If muscle spasm is centrally mediated, patients will also not respond well to MET. Patients need to be cooperative to follow the instructions required for this technique.

Equipment

MET with post-isometric relaxation is a hands-on osteopathic manipulative treatment that necessitates a stable, firm surface, preferably an adjustable height cushioned table for optimal treatment positioning and patient and physician comfort

Personnel

MET with post-isometric relaxation requires a qualified provider trained in muscle energy techniques.

Preparation

After thoroughly discussing the risks, benefits, and alternative treatment options, obtaining informed patient consent is imperative for any procedure, including MET and osteopathic manipulative therapy. Before initiating physical contact with the patient, the provider should clearly explain the procedures they will perform. The treatment process commences with a comprehensive static and dynamic evaluation of the segments within the thoracic spine. Clinicians may employ soft tissue techniques as a prelude to direct techniques like MET with post-isometric relaxation, particularly when significant muscle texture changes are present.[14]

Technique or Treatment

The targetted segment must be localized and isolated when treating the thoracic spine with MET. In the upper thoracic spine (T1-T4), it is common to use the head and neck as a lever. The lower thoracic spine segments (T5-T12) can be localized by manipulating the position of the patient's trunk. Localizing the dysfunctional segment involves monitoring the posterior transverse process for motion throughout the treatment through palpation. Post-isometric relaxation is the type of MET most commonly used. The patient is placed into the barrier and asked to resist motion toward freedom.

Muscle Energy Technique With Post-Isometric Relaxation

Example Osteopathic Diagnosis: T3 flexed, rotated right, and sidebent right.

Step 1. The treatment can be performed with the patient either seated or supine. In the seated approach, the patient sits, and the clinician stands behind the patient. As this is an upper thoracic segment, the head will be used as a lever to affect motion on T3. The right hand will monitor the transverse process of T3.

Step 2. The clinician extends the patient's head, side bends, and rotates it to the left until motion can be felt at T3 to engage the barrier. It is essential to position the patient in a way that engages the articular barrier, not just causing fascial tightening.

Step 3. The patient is instructed to gently but continuously attempt to return his head to an upright, neutral position while the clinician applies an equal counterforce. This position is maintained for 3 to 5 seconds before instructing the patient to relax and remain in place. The patient must stay relaxed for 3 to 5 seconds before engaging a new barrier. By alternating the contraction and relaxation before engaging a new barrier, the Golgi tendon fibers and muscle spindle fibers are engaged to allow for the lengthening of the agonist muscle and relaxation of the antagonist muscle.

Step 4. Repeat the previous step 3 to 5 times with a passive stretch into the restrictive barrier with no patient involvement following the final round of treatment. Passively return the patient to a neutral position.

Step 6. Reassess for improvement in symmetry of the treated segment by palpating the transverse processes of T3 for the example given.

Technical Pearls

When treating the lower thoracic segment, it is easier to maneuver the patient around if her arms are crossed and the clinician sidebends her by pushing down on the ipsilateral shoulder using the axilla. When treating type 1 somatic dysfunctions (eg, T3-6 neutral, side bent right, and rotated left), the curve's apex is treated first.

T12 is challenging to treat as the facets below and above face in different directions. The thoracic facets of the vertebrae face posteriorly, upwards, and laterally. However, lumbar facet joints (L1) face posteriorly, upward, and medially. When using MET, it is essential to localize precisely.

Complications

Patients undergoing MET with post-isometric relaxation treatment should understand they may experience muscle soreness and fatigue after treatment. The clinician may suggest increasing water intake following treatment. Excessive force can result in complications such as tendon avulsion or rib fracture. To mitigate the force in post-isometric relaxation, the patient must be asked to resist just enough to engage the treated segment.

Clinical Significance

Somatic dysfunction of the thoracic spine commonly results in back pain and discomfort, causing patients to seek medical advice. Osteopathic techniques, including MET, provide a conservative, nonpharmacological avenue for alleviating pain and correcting musculoskeletal somatic dysfunctions in the thoracic spine, leading to an increased range of motion in affected joints.[3][15]

MET with post-isometric relaxation creates necessary soft tissue relaxation to help with high-velocity, low-amplitude techniques. MET can also help resolve hypertonic tissue before myofascial release techniques.

Enhancing Healthcare Team Outcomes

Understanding of osteopathic medicine has grown as more osteopathic physicians practice in the United States. However, many patients and healthcare workers remain unfamiliar with MET and its role in medicine. The patient's active involvement in the contraction and relaxation phases, along with precise positioning, contributes to successful MET with post-isometric relaxation treatment. Understanding the roles of MET with post-isometric relaxation and osteopathic manipulative treatment in symptom management is essential for healthcare teams, as they can offer safe and effective relief for patients when administered by skilled providers in appropriate situations.