What causes trigger points? Part 2

The Primary Cause of Trigger Points is Muscular Overload

As a Toronto RMT I am constantly working to release trigger points.  Trigger points are one of the most common causes for muscular pain and discomfort. In my previous blog, Trigger points part 1, we discussed what a trigger point actually is, and how it forms.  We also briefly discussed that the most common cause of a trigger point is  usually some sort of muscular overload. In this post I will elaborate a bit more.

To most people, the term muscular overload probably conjures up images of physical strain on the muscle tissue and its tendons, but in trigger point therapy the term has a dual interpretation. While the physical load imposed on a muscle does play a role in trigger point formation, an equally important factor is the demand placed on the neuromuscular control mechanism of the muscle. ( remember that muscular end plate) This mechanism is responsible for taking the electrical impulse of a nerve and transforming it into a biochemical signal that both controls and powers muscular activity. The complex nature of this electrochemical process makes it the “weak link in the chain” of muscular functioning, and the failure of a muscle’s control mechanism is responsible for the activation of trigger points.

Understanding The Different Types of Muscular Overload that cause trigger points

Muscular overload comes in several different flavors, some are obvious, while others are a bit more elusive. Let’s take a closer look at each type of muscular overload:

  • Exertion Overload: This is the most obvious form of muscular overload and simply means that a muscle was not strong enough to perform a task required of it. For example, bending at the waist to lift a heavy object is likely to create an exertion overload in the low back muscles. Trigger point activity resulting from this type of overload is more prominent in unconditioned muscles. People who partake in resistance training (lifting weights) are likely to develop exertion related trigger points when the just begin training, or return to it after a long hiatus. Most of the time, this type of overload occurs in a sudden fall, when a person tries to brace against an impact.
  • Overuse or Repetitive Stress Overload: An overload of this type is probably the most common cause of trigger point activity, though this is just my personal estimate. In these cases, the muscle’s functional endurance is exceeded by a given task. Examples include performing repetitive movements at a job day after day, sporting activities, and gardening. Often the pain associated with overuse injuries is attributed to tendonitis, but I find it remarkable how many cases of tendonitis can be indirectly resolved with trigger point therapy, by a qualified RMT.
  • Biomechanical Overload: Muscles work together in functional groupings called myotatic units to create bodily movement. For any given movement, the muscles within a myotatic unit can be classified into two groups: synergists and antagonists.  Synergistic muscles work together to produce a specific bodily movement, while antagonistic muscles act to produce the opposing bodily movement. Biomechanical overload occurs when one of the muscles in a myotatic unit is weakened by trigger point activity. In this situation, a synergistic muscle becomes overloaded by the additional work load that it must take on because of its dysfunctional partner, and an antagonistic muscle becomes overloaded by a distortion in the nerve supply controlling it. Trigger point formation in a muscle due to biomechanical overload occurs frequently in established myofascial pain disorders, and must be recognized to treat these disorders effectively.
  • Postural Overload: One of the more subtle ways of overloading a muscle is to place it in an over-shortened or overstretched state for a prolonged period of time.This type of overload, termed postural overload, can be either of a mechanical or neurological nature, and is closely related to biomechanical overload. There are two very common types of postural overload that cause trigger points to form within a muscle; antalgic and degenerative.

Antalgic postural overloads occur when a person holds their body in a certain manner to avoid the pain from an injury. For example, a person may hold their head to one side to diminish the pain from a neck cramp, or lean their trunk forward to avoid aggravating a backache.

Degenerative postural overloads occur secondarily to the long-term changes in posture associated with aging or disease. Examples include an exaggerated sway in the lower back, or the forward head and sunken chest posture so frequently seen in older adults.

In either type of postural overload, some muscles are kept in abnormally shortened position, while others are kept in an abnormally elongated position, predisposing both groups of muscles to the development of trigger points.

  • Referred Pain Overload: Pain that is referred to a muscle from trigger points in other muscles, or from joints and internal organs, can overload a muscle’s control mechanism and cause trigger points to form within it. In trigger point therapy, trigger points that develop secondarily to the referred pain from other trigger points are called satellite trigger points. Any myofascial disorder that is more than 2 days old, is likely to involve satellite trigger point activity. If the referred pain is severe enough, muscle tension associated with an unconscious guarding reflex may also produce trigger point activity in the local muscles.
  • Muscle Trauma Overload: Physical trauma to a muscle, like that which might occur during a fall or automobile accident, can directly activate trigger points in that muscle. This may occur from a reflex response to the pain associated with the tissue damage, or because of an impairment in the muscle’s functional capacity.

Factors That Predispose A Muscle To Overload

The following is a list of factors that can make a muscle particularly susceptible to the types of muscular overload discussed above. In cases where trigger point activity returns shortly after treatment, one should investigate these conditions for a likely cause.

  • Muscle Tension: Anything that increases a muscle’s tension also makes it more susceptible to muscular overload. Emotional stress can create significant tension in the neck, shoulder, and abdominal muscles, making these muscles hot-spots of trigger point activity. One frequently overlooked source of muscular tension results from chilling the muscle, like that which might occur when sleeping under a ceiling fan. I see this a lot in the early summer when people start sleeping with their Air conditioning on.  Some neurological disorders, like strokes, can cause abnormalities in muscle tension as well.
  • Structural Inadequacies: This term refers to abnormalities in the skeletal structure that can cause some muscles to be chronically overworked when trying to compensate for them. Examples include having one leg that is longer than the other (a lower limb-length  inequality), pelvic bone asymmetries, short upper arms, and a Morton foot structure (short big toe-long second toe).
  • Nutritional Deficiencies: Myofascial pain disorders can be perpetuated by deficiencies in the water-soluble vitamins B1, B6, B12, folic acid, and vitamin C. These micronutrients play important roles in the physiology of muscular activity and nearly half of chronic myofascial pain disorder cases require dietary supplementation for successful treatment. Additionally, dietary imbalances in calcium, potassium, and iron may also perpetuate trigger point disorders, and must be corrected to achieve long-term treatment success in some cases.
  • Metabolic Disorders: Any abnormality in the energy metabolism of a muscle can make it hypersensitive to overload stress. Systemic metabolic disorders such as hypothyroidism and hypoglycemia can contribute significantly to the perpetuation of trigger point activity in muscles throughout the body.
  • Chronic Bacterial Infections: Dental abscesses, sinusitis, and urinary tract infections may negate the treatment of trigger points, and must be ruled out in relevant cases.
  • Viral Diseases: Systemic viral conditions such as the flu or herpes simplex virus 1 (not genital herpes) need to be addressed prior to the treatment of trigger point disorders.


Although these are all common causes of muscular overload, and trigger point development, there are always exceptions.  This is why it is important to seek the help of a qualified therapists, such as a RMT ( registered massage therapist) to help assess and treat your trigger point pain.

In my next post, trigger points part 3: How massage therapy can help, I will discuss how massage therapy can help treat trigger