Injuries, stress, inflammation, trauma, and poor posture can cause restriction to fascia. Since fascia is an interconnected web, the restriction or tightness to fascia at a place, with time can spread to other places in the body like a pull in a sweater. The goal of myofascial release is to release fascia restriction and restore its tissue health.
In medical literature, the term myofascial was used by Janet G. Travell M.D. in the 1940s referring to musculoskeletal pain syndromes and trigger points. In 1976 Dr. Travell began using the term "Myofascial Trigger Point" and in 1983 published the famous reference "Myofascial Pain & Dysfunction: The Trigger Point Manual". Some practitioners use the term "Myofascial Therapy" or "Myofascial Trigger Point Therapy" referring to the treatment of trigger points, this is usually in medical-clinical sense.
Here the term Myofascial Release refers to soft tissue manipulation techniques. It has been loosely used for different manual therapy, soft tissue manipulation work (connective tissue massage, soft tissue mobilization, Rolfing, strain-counterstrain etc). There are two main schools of myofascial release: the direct and indirect method.
Trigger points are described as hyperirritable spots in skeletal muscle that are associated with palpable nodules in taut bands of muscle fibers. The palpable nodules are said to be small contraction knots and a common cause of pain. Compression of a trigger point may elicit local tenderness, referred pain, or motor dysfunction.
According to proponents of the concept, a trigger point does not really cause a contraction, but rather causes a contracture. A contraction is muscular activity mediated by the nervous system, while a contracture is said to be a mechanical "sticking" of the muscle fibers with no involvement from the nervous system. The hypothesis is that usually an event of muscular overload causes a prolonged release of Ca2+ ion from the sarcoplasmic reticulum (storage unit for the muscle cell) which results in a sticking of the untrained or overloaded cells. This leads to a compression of capillaries and results in an increased local energy demand and local ischemia (loss of blood circulation) to the area. This "energy crisis" (as it is termed in the seminal work on trigger points) causes the release of chemicals that augment pain activity. Since an involved muscle is weakened by this theorised sustained shortening, surrounding muscles themselves may develop trigger points in a compensatory fashion.
Trigger points have been a subject of study by a small number of doctors for several decades although this has not become part of mainstream medicine. The existence of tender areas and zones of induration in muscles has been recognized in medicine for many years and was described as muscular rheumatism or fibrositis in English; German terms included myogelose and myalgie. However, there was little agreement about what they meant. Important work was carried out by J. H. Kellgren at University College Hospital, London, in the 1930s and, independently, by Michael Gutstein in Berlin and Michael Kelly in Australia (the latter two workers continued to publish into the 1950s and 1960s). Kellgren conducted experiments in which he injected saline into healthy volunteers and showed that this gave rise to zones of referred extremity pain.
Today, much treatment of trigger points and their pain complexes are handled by massage therapists, physical therapists, osteopaths, occupational therapists, myotherapists, some chiropractors and acupuncturists, and other hands-on somatic practitioners who have had experience or training in the field of neuromuscular therapy (NMT).
Janet G. Travell, MD
It was, however, an American physician, Janet G. Travell, who was responsible for the most detailed and important work. Her work treating US President John F. Kennedy's back pain was so successful that she was asked to be the first female Personal Physician to the President. She published more than 40 papers between 1942 and 1990 and in 1983 the first volume of The Trigger Point Manual appeared; this was followed by the second volume in 1992. In her later years Travell collaborated extensively with her colleague David Simons. A third edition is soon to be published by Simons and his wife, both of whom have survived Travell.
The trigger point concept remains unknown to most doctors and is not generally taught in medical school curricula. Other health professionals, such as physiotherapists, osteopaths, naturopaths, chiropractors, physiatrists, massage therapists and stuctural integrators and some veterinarians are generally more aware of these ideas and many of them make use of trigger points in their clinical work.
Travell and Simon's seminal work on the subject, Myofascial Pain and Dysfunction: The Trigger Point Manual, states the following:
around 75% of pain clinic patients have a trigger point as the sole source of their pain.
The following conditions are often diagnosed (incorrectly) when trigger points are the true cause of pain: carpal tunnel syndrome, bursitis, tendinitis, angina pectoris, sciatic symptoms, along with many other pain problems.
Arthritis is often cited as the cause for pain even though pain is not always concomitant with arthritis. The real culprit may be a trigger point, normally activated by a certain activity involving the muscles used in the motion, by chronically bad posture, bad mechanics, repetitive motion, structural deficiencies such as a lower limb length inequality or a small hemipelvis, or nutritional deficiencies.
Myofascial pain syndrome
The main innovation of Travell's work was the introduction of the myofascial pain syndrome concept. This is described as a focal hyperritability in muscle that can strongly modulate central nervous system functions. Travell and followers distinguish this from fibromyalgia, which is characterized by widespread pain and tenderness and is described as a central augmentation of nociception giving rise to deep tissue tenderness that includes muscles. It is said to be considerably more difficult to treat.
Qualities of trigger points
Trigger points have a number of qualities. They may be classified as active/latent and also as key/satellites and primary/secondary.
An 'active trigger' point is one that actively refers pain either locally or to another location (most trigger points refer pain elsewhere in the body along nerve pathways). A latent trigger point is one that exists, but does not yet refer pain actively, but may do so when pressure or strain is applied to the myoskeletal structure containing the trigger point.
A key trigger point is one that has a pain referral pattern along a nerve pathway that activates a latent trigger point on the pathway, or creates it. A satellite trigger point is one which is activated by a key trigger point. Successfully treating the key trigger point often will resolve the satellite and return it from being active to latent, or completing treating it too.
In contrast, a primary trigger point in many cases will biomechanically activate a secondary trigger point in another structure. Treating the primary trigger point does not treat the secondary trigger point.
Activation of trigger points may be caused by a number of factors, including acute or chronic muscle overload, activation by other trigger points (key/satellite, primary/secondary), disease, psycho-emotional disorders, homeostatic imbalances, direct trauma to the region, radiculopathy, infections and health choices such as smoking.
Trigger points can appear in many myofascial structures including muscles, tendons, ligaments, skin, joint capsule, periosteal, and scar tissue. When present in muscles there is often pain and weakness in the associated structures. These pain patterns in muscles follow specific nerve pathways and have been readily mapped to allow for identification of the causative pain factor. Many trigger points have pain patterns that overlap, and some create reciprocal cyclic relationships that need to be treated extensively to remove them.
Diagnosis of trigger points is by examining signs, symptoms, pain patterns and manual palpation. Usually there is a taut band in muscles containing trigger points, and a hard nodule can be felt. Often a twitch response can be felt in the muscle by running your finger perpendicular to the muscle's direction; this twitch response often activates the "all or nothing" response in a muscle that causes it to contract. Pressing on an affected muscle can often refer pain. Clusters of trigger points are not uncommon in some of the larger muscles, such as the Gluteus group (Gluteus Maximus, Gluteus Medius, Gluteus Minimus). Often there is a heat differential in the local area of a trigger point, and many practitioners can sense that.
In order for a medical sign to be diagnostically useful, independent examiners must be able to agree on its presence (see intersubjective verifiability). A study by Gerwin et al. found that independent examiners were generally able to identify myofascial trigger points (MTrP), but only with sufficient training and agreement on the definition and features of MTrP's. Gerwin et al. said:
Three previous studies (Nice et al., 1992; Wolfe et al., 1992; Njoo and Van der Does, 1994) have examined this problem, and none of them could establish the reliability of MTrP examination in all of its major manifestations. ... The present study shows that four examiners can achieve statistically significant agreement, at times almost perfect agreement, about the presence or absence of five major features of the MTrP and on the presence or absence of the TrP, whether it be latent or active. This establishes the MTrP as a reliable clinical sign. The present study also shows that these features are identified with greater or lesser reliability depending on the specific feature and the specific muscle being examined. ... A training period was found to be essential in order to achieve these results.
There have been several theories about trigger points. It was once believed that trigger points were scars or inflammation in the muscle. This was disproved when biopsies showed no abnormalities. 
More recently it has been proposed that trigger points are spasms or contractures of voluntary muscle, possibly caused by an abnormality at the neuromuscular junction where the nerves controlling muscles connect to the muscle fibers (Travell & Simon). This theory seems unlikely because no contractions of voluntary muscle have been identified by traditional EMG and because the trigger points are often not in the location of the neuromuscular junction.
The most recent theory is that trigger points are muscle spindles, made over-active by adrenalin stimulation. These very short muscle fibers, only about 1 cm in length, are called intrafusal muscle fibers to distinguish them from the voluntary muscle fibers which are called extrafusal muscle fibers. Only the intrafusal muscle fibers inside the spindle are activated by adrenalin via the sympathetic nervous system which also controls heart rate, blood pressure and other internal regulatory functions. The “sympathetic spindle spasm” theory of trigger points proposes that when spindles are over-activated by adrenalin they become painful. A clinical research trial is being conducted and should be completed by the end on 2006 by Dr. David Hubbard in San Diego, California. Paul Svacina, Engineer and bodyworker also in California, believes that this theory supports the idea that stress and decrease of moderate physical activity in modern lives has increased the occurrence of myofascial pain and trigger points.
Current theories include:
Travell’s Initial Trauma Theory
Integrated Trigger Point Hypothesis
Muscle Spindle Hypothesis
Fibrotic Scar Tissue Hypothesis
Prior to treatment commencement, the therapist should be sure be that the pain patterns they are treating lend themselves to Trigger point therapy. If the patient presents with swelling, discoloration or neurological signs and symptoms, it is always advisable to refer to another health/medical care provider regarding further examination and/or investigation. The therapist should be aware of his/ her professional limitations.
Treatment of trigger points may be by manual massage (deep pressure as in Bonnie Prudden's approach or tapotement as in Dr. Griner's approach), mechanical vibration, pulsed ultrasound, electrostimulation , ischemic compression, manual trigger point release technique , injection of saline, CO2 or local anesthetic such as procaine hydrocloride (novocain), dry-needling without anesthetic or saline, "spray-and-stretch" using a cooling (vapocoolant) spray, and stretching techniques that invoke reciprocal inhibition within the musculoskeletal system. Use of elbows, feet or various tools to direct pressure directly upon the trigger point often occurs, to save practitioner's hands. Practitioners of medical acupuncture often use trigger points as the basis for their treatment and studies have shown a considerable similarity between the locations of trigger points and classic acupuncture points. (Some acupuncture points and trigger points seem to overlap, however experts such as John Harris and Paul Svacina do not agree with the previous claim.)
A successful treatment protocol relies on identifying trigger points, resolving them and, if all trigger points have been deactivated, elongating the structures affected along their natural range of motion and length. In the case of muscles, which is where most treatment occurs, this involves stretching the muscle using combinations of passive, active, active isolated (AIS), muscle energy techniques (MET), and proprioceptive neuromuscule facilitation (PNF) stretching to be effective. Fascia surrounding muscles should also be treated, possibly with myofascial release, to elongate and resolve strain patterns, otherwise muscles will simply be returned to positions where trigger points are likely to re-develop.
Injections have shown the quickest response, however they are not convenient and have side effects. The results of manual therapy are related to the skill level of the therapist. If trigger points are pressed too short a time, they may activate or remain active; if pressed too long or hard, they may be irritated or the muscle may be bruised, resulting in pain in the area treated. This bruising may last for a 1-3 days after treatment, and may feel like, but is not similar to, delayed onset muscle soreness (DOMS), the pain felt days after overexerting muscles. Pain is also common after a massage if the practitioner uses pressure on unnoticed latent or active trigger points, or is not skilled in Trigger Point Therapy. Further pain after one to three treatment sessions by a Trigger Point practitioner should be referred to a medical professional. Evidence based medicine researchers have concluded evidence for the usefulness of trigger points in the diagnosis of fibromyalgia is thin.  Fibromyalgia patients generally have multiple, reocurring trigger points, typically in a quadrant or more of the body.
There are a number of ways to self-treat trigger points and these methods are described in numerous texts. It should be noted that due to the controversy related to this field, as well as its relative newness, that no single guide should be taken as the sole or final truth. Underlying any attempts at self-treatment should be a working knowledge of the area to be treated, especially with regard to the musculature, nerves, glands and vessels.
Trigger points in the male or female pelvis, such as found in chronic pelvic pain syndrome (CPPS), should be treated by medical doctors or osteopaths trained in the use of intra-rectal trigger point and myofascial release techniques.
Caution: Self treatment does have some inherent dangers of damaging soft tissue and other organs. The trigger points in the upper Quadratus Lumborum, for instance, are very close to the kidneys and poorly administered self treatment may lead to kidney damage. Likewise, treating the masseter muscles may damage the salivary glands superficial to this muscle. Furthermore, and some experts believe trigger points may develop as a protective measure against unstable joints. A qualified professional should eliminate this cause prior to beginning a self treatment program.
^ Simons, D.G. Cardiology and Myofascial Trigger Points: Janet G. Travell's Contribution . Tex Heart Inst J. 2003; 30(1): 3–7.
^ Bagg J, (2003),The President's Physician,Texas Heart Institute, Houston
^ Swedish Medical Center
^ American Academy of Family Physicians
^ Dynamic Chiropractic
^ Gerwin RD, Shannon S, Hong CZ, Hubbard D, Gevirtz R. Interrater reliability in myofascial trigger point examination. Pain. 1997 Jan;69(1-2):65-73.