Understanding How IMS Can Help Relieve Chronic Pain

Intramuscular Stimulation (IMS), also known as Gunn IMS, is a Canadian- developed dry needling technique used by specially trained physiotherapists to assess and treat persistent musculoskeletal pain. Developed in the 1970s by Vancouver physician Dr. Chan Gunn while working with the Workers’ Compensation Board of British Columbia, Gunn IMS is based on a neuropathic model of pain that looks beyond the site of symptoms to identify dysfunction within the nervous system that may be contributing to ongoing muscle pain and movement impairment. Today, the Gunn IMS education program is delivered through the University of British Columbia Faculty of Medicine and trains experienced physiotherapists and physicians in this comprehensive assessment and treatment approach.

Unlike treatments that focus solely on relieving pain, IMS aims to identify and address the underlying source of symptoms. A detailed physical assessment is used to identify muscles that have become shortened, tight, or hypersensitive due to altered nerve function. The goal is not simply to needle where it hurts, but to restore healthier muscle function and reduce the factors contributing to persistent pain.

To understand how IMS works, it helps to first understand the different stages of pain. Immediate pain is the body’s protective response to a sudden stimulus, such as touching a hot stove. Acute pain follows an injury and is typically accompanied by redness, swelling, inflammation, and tenderness. In most cases, acute pain is self-limiting and resolves as healing occurs. Chronic pain, however, is different. It may persist long after tissues have healed and can involve ongoing inflammation, nervous system sensitization, or changes within the central and peripheral nervous systems, such as neuropathic or radiculopathic pain.

As pain becomes chronic, the nervous system can become sensitized. During the early stages of inflammation, the body releases chemicals that increase blood flow and make pain receptors (nociceptors) more sensitive. These changes are important because they help protect injured tissues and initiate healing. However, if inflammatory chemicals persist or the nervous system remains sensitized, even normal daily activities can become painful despite little or no ongoing tissue damage.

IMS targets myofascial trigger points, which are tight, irritable bands within muscle tissue. When a needle stimulates one of these trigger points, it may produce a local twitch response, a brief involuntary contraction of the muscle. Research suggests that this twitch response may help reduce pain within the affected muscle, increase the pain threshold, and decrease spontaneous electrical activity associated with muscle tightness. Although the twitch occurs locally, studies have also demonstrated regional and even bilateral effects, meaning changes may occur in other muscles supplied by the same nerve root.

While some people associate dry needling with significant discomfort, treatment should be individualized. Stimulating too many trigger points during a single session may further irritate already hypersensitive tissues. An experienced physiotherapist will carefully determine the appropriate number of treatment sites based on each patient’s presentation and sensitivity.

One proposed mechanism behind IMS involves creating a small, controlled mechanical stimulus within the muscle. This minor irritation is thought to initiate a localized healing response and may influence the body’s natural electrical activity involved in tissue repair. While additional research continues to investigate these mechanisms, the treatment is believed to support tissue recovery over several days following needling.

Another important concept in IMS relates to nerve health. When the normal flow of nerve impulses is disrupted by conditions such as spinal joint degeneration, disc bulges, chronically tight spinal muscles, or nerve root compression, the tissues supplied by those nerves—including muscles, tendons, ligaments, blood vessels, skin, and bone—may receive less neural input (ie. less nutrition). Some IMS theories suggest this diminished input can contribute to muscle dysfunction such as chronic tendinopathies or degenerative muscle tears.

The therapeutic effects of IMS are thought to involve several complementary mechanisms. Mechanically, the needle stimulates muscle tissue and sensory receptors. Electrically, it may influence nerve activity and cellular signalling associated with healing. Chemically, it may help reduce local concentrations of inflammatory and pain-producing substances. Finally, improvements in nerve function may enhance the normal physiological support that nerves provide to healthy tissues (better nutrition to all the tissues that nerve supplies!).

IMS is most effective when incorporated into a comprehensive physiotherapy treatment plan that includes education, movement, strengthening, and manual therapy where appropriate. By identifying the source of muscle dysfunction rather than simply masking symptoms, IMS can be a valuable tool for helping individuals reduce pain, improve movement, and return to the activities that matter most.

Jennifer Gordon
(BSc.PT, GunnIMS, AFCI)
Physiotherapist – Bragg Creek Physiotherapy
www.braggcreekphysio.com