Myofascial pain syndrome (MPS) develops when hyperirritable spots called trigger points form within tight bands of muscle fiber, causing localized and referred pain. Approximately 9 million people in the United States have it, and MPS is the primary source of pain in up to 85% of patients seen at chronic pain centers. The causes range from repetitive physical strain and poor posture to stress, nutritional deficiencies, and disrupted sleep, often working together to create a self-reinforcing cycle.
The Energy Crisis Inside the Muscle
The most widely accepted explanation for trigger point formation is known as the energy crisis hypothesis. It starts with excessive mechanical force on a muscle, whether from a sudden overload, a forceful contraction, or repetitive low-level activity over time. That strain damages muscle fibers at the microscopic level, leading to a cascade of events at the point where nerves signal muscles to contract (the motor endplate).
Under normal conditions, a nerve releases a small amount of a chemical messenger called acetylcholine to tell a muscle fiber to contract, and the fiber relaxes once the signal stops. In a trigger point, that system breaks down. Too much acetylcholine floods the endplate, driven by abnormal spontaneous release and amplified by the sympathetic nervous system (your body’s fight-or-flight wiring). At the same time, the enzyme that normally clears acetylcholine away is suppressed, and the muscle fiber’s receptors for the signal are dialed up. The result is a small patch of muscle that stays locked in contraction without being told to relax.
That sustained contraction squeezes the tiny blood vessels feeding the area, cutting off oxygen and nutrient supply. Without adequate blood flow, the muscle cells can’t produce the energy (ATP) needed to release the contraction. Cells become damaged, and the body responds by releasing inflammatory molecules, including bradykinin, substance P, and other compounds that activate pain-sensing nerve endings. Those pain signals feed back into the nervous system, which can increase muscle tension further, and the cycle continues. This is why a trigger point, once established, rarely resolves on its own without intervention.
Repetitive Motion and Poor Posture
The most common trigger for MPS is muscle overuse with poor form. Repetitive motions used in jobs or hobbies, such as typing, assembly line work, playing a musical instrument, or overhead reaching, subject the same muscle groups to sustained low-level strain. Over hours and days, that strain accumulates, making trigger points more likely to form in the overworked fibers.
Poor posture compounds the problem. Slouching at a desk, carrying a bag on one shoulder, or holding a phone between your ear and shoulder forces certain muscles to stay partially contracted for long periods. Weak muscles that can’t adequately support the body’s weight or movement patterns are especially vulnerable. A muscle that’s chronically shortened or lengthened beyond its comfortable range is primed for trigger point development, which is why MPS so frequently affects the neck, shoulders, and upper back in people with desk jobs.
Stress and the Nervous System
People who frequently feel stressed or anxious are more likely to develop trigger points. The connection is partly behavioral: stress causes unconscious muscle clenching, particularly in the jaw, neck, and shoulders. That habitual clenching is a form of repetitive strain, creating the same conditions as physical overuse.
But stress also works through deeper biological pathways. The sympathetic nervous system, which ramps up during stress, directly increases acetylcholine release at motor endplates and promotes sustained muscle contraction. Research on patients with temporomandibular disorders (jaw-related myofascial pain) has found evidence of dysfunction in the body’s stress hormone system, specifically abnormally low cortisol levels. This pattern, called hypocortisolism, is also seen in fibromyalgia and chronic fatigue syndrome. When the body’s stress-regulation system is disrupted, it loses the ability to properly dampen inflammation and pain signaling, making trigger points more persistent and painful.
Sleep Quality and the Pain Cycle
Poor sleep both results from and contributes to myofascial pain. A study of people with mechanical neck pain found a strong correlation between sleep quality and pain intensity: worse sleep was associated with more severe pain and greater disability. The relationship likely works in both directions. Pain disrupts sleep, and inadequate sleep lowers the body’s pain threshold, reduces muscle recovery, and increases sensitivity to mechanical stress. For someone with active trigger points, a few nights of poor sleep can make existing pain significantly worse and make the muscles more susceptible to developing new trigger points.
Vitamin D and Nutritional Gaps
Low vitamin D levels appear frequently in people with MPS. In one study comparing 120 patients with myofascial pain to healthy controls, the patients had vitamin D levels averaging 12.8 ng/mL, roughly half the control group’s average of 22.8 ng/mL. Over 80% of the patients in that study were vitamin D deficient (below 20 ng/mL). Vitamin D plays a role in muscle function and inflammation regulation, so a deficiency may make muscles more vulnerable to the biochemical dysfunction that produces trigger points. While correcting a deficiency won’t necessarily eliminate MPS on its own, it removes one factor that may be keeping the cycle going.
How MPS Differs From Fibromyalgia
Because both conditions involve muscle pain, MPS and fibromyalgia are easy to confuse. The key distinction is location and behavior. MPS pain is regional, tied to specific trigger points in identifiable muscles. Pressing on one of those points produces a predictable pattern of referred pain, and sometimes a visible muscle twitch. The pain stays in a defined area and can often be traced back to a particular muscle injury or overuse pattern.
Fibromyalgia pain is diffuse, affecting both sides of the body above and below the waist, and it migrates from one area to another over time. Researchers believe fibromyalgia reflects a problem with how the brain processes pain signals, amplifying sensations rather than generating them from a specific muscle. Fibromyalgia also causes symptoms beyond pain, including persistent fatigue even after long sleep, and difficulty with concentration and mental focus. Diagnosing fibromyalgia requires ruling out other conditions through blood tests and meeting specific criteria for widespread pain lasting at least three months. MPS, by contrast, can often be identified through physical examination alone.
How Trigger Points Are Identified
An international consensus of pain experts established three core findings for diagnosing a trigger point: a taut band of muscle, a hypersensitive spot within that band, and referred pain (pain felt in a predictable location away from the trigger point itself). At least two of these three should be present for a diagnosis. A visible muscle twitch when the trigger point is pressed and a “jump sign” (an involuntary flinch from the patient) are considered supportive evidence but aren’t required, partly because the twitch response is difficult to detect reliably.
Trigger points are further classified as active or latent. An active trigger point reproduces a symptom you already recognize as part of your pain pattern, even if it’s not bothering you at the moment of the exam. A latent trigger point hurts when pressed but doesn’t produce a symptom you’d identify as familiar. Both types involve the same underlying muscle dysfunction, but active trigger points are the ones driving your day-to-day pain.
Why Multiple Factors Matter
MPS rarely has a single cause. More often, several contributing factors overlap. Someone with a desk job (sustained posture), high work stress (muscle clenching and nervous system activation), poor sleep (reduced recovery), and low vitamin D (impaired muscle function) is far more likely to develop persistent trigger points than someone with just one of those risk factors. This is also why treatment that targets only one dimension, such as massage without addressing posture, or posture correction without managing stress, often produces only temporary relief. The most effective approaches address the full picture: the mechanical strain, the biochemical environment, and the nervous system inputs that keep trigger points alive.