Intramuscular stimulation (IMS) in physiotherapy is a dry needling technique used to treat chronic muscle pain and tension caused by neuropathy. A trained physiotherapist inserts sterile, thin, filament-like needles directly into tight bands of muscle or trigger points. The needles contain no medication or fluid. IMS stimulates a stretch reflex that causes the tight muscle to contract briefly and then fully relax, which reduces pain, restores range of motion, and desensitises the hypersensitive nerve driving the muscle tightness. IMS was developed by Dr. Chan Gunn, a clinical professor who taught the technique at the University of British Columbia’s medical school and the University of Washington’s Multidisciplinary Pain Centre.

This blog explains how IMS works, what it treats, what it feels like, how it differs from acupuncture, who should and should not receive it, and what the research says about its effectiveness. Whether you are exploring IMS as a treatment option or simply want to understand what it involves, this guide covers the full picture.

How Does IMS Work?

IMS works by inserting a thin, solid acupuncture needle into a shortened, supersensitive muscle to trigger a reflex relaxation response. The needle targets the muscle’s trigger point, which is a tight, contracted band of fibres that produces pain, restricts movement, and compresses the surrounding nerves, tendons, and joints.

The mechanism behind IMS involves three distinct physiological effects. First, the needle stimulates what is called the stretch reflex. When the needle enters the shortened muscle, it causes the muscle fibres to wrap around the needle and pull on receptors called muscle spindles. The spindle activation produces a brief, involuntary contraction followed by a reflex relaxation that lengthens the muscle. Patients often feel this as a deep cramp or twitch that fades within seconds. Second, the needle stimulation desensitises the spinal nerve that controls the affected muscle. Neuropathic pain occurs when nerves become irritable and send exaggerated pain signals even without tissue damage. IMS interrupts this cycle by resetting the nerve’s sensitivity threshold. Third, the needle creates a controlled micro-injury in the muscle tissue that triggers the release of platelet-derived growth factor (PDGF), a chemical in the blood that initiates a localised healing response. PDGF promotes tissue repair and helps restore the normal chemical relationship between the nerve and the muscle it controls.

These three effects, muscle relaxation through the stretch reflex, nerve desensitisation, and a fresh healing response, work together to address the root cause of chronic muscle pain rather than masking the symptom. This is why IMS often succeeds for patients whose pain has not responded to conventional treatments like medication, massage therapy, or standard stretching.

What Is the Difference Between IMS and Acupuncture?

The difference between IMS and acupuncture is the theoretical framework and the treatment target. IMS is based on western neurophysiological principles and targets anatomically identified trigger points in shortened muscles, while traditional acupuncture is based on traditional Chinese medicine (TCM) principles and targets points along energy meridians to restore the flow of qi (vital energy) through the body.

Both techniques use the same type of thin, sterile, solid needle. Both are performed by trained practitioners and both can reduce pain. The similarity in needles is where the overlap ends. IMS practitioners select needle insertion sites based on a physical examination that identifies shortened muscles, tender motor points, and signs of nerve irritation along specific spinal segments. Acupuncture practitioners select points based on TCM diagnostic methods that assess energy flow patterns, pulse quality, and tongue appearance. IMS produces a local twitch response in the muscle, which confirms that the needle has reached the trigger point. Acupuncture does not typically produce this response because it targets different tissue depths and locations.

Contemporary medical acupuncture, which is used by many physiotherapy practitioners in Canada, blends elements of both approaches. It applies acupuncture needles using western anatomical reasoning rather than TCM meridian theory. Some physiotherapists trained in contemporary medical acupuncture use needle techniques that overlap with IMS principles, particularly when targeting myofascial trigger points for pain relief.

What Is the Difference Between Dry Needling and IMS?

The difference between dry needling and IMS is primarily in origin and training certification, not in the needle or the basic technique. Dry needling is the broader category that describes any technique using a solid, dry needle (containing no medication) inserted into muscle tissue to treat pain and dysfunction. IMS is a specific form of dry needling developed by Dr. Chan Gunn that follows a particular diagnostic and treatment model focused on neuropathic pain and segmental spinal nerve involvement. All IMS is dry needling, but not all dry needling is IMS. Practitioners certified through Dr. Gunn’s Institute for the Study and Treatment of Pain (iSTOP) follow the Gunn IMS protocol specifically. Other dry needling certifications, such as those from Functional Dry Needling or Kinetacore programmes, teach related but distinct approaches to trigger point treatment.

What Conditions Does IMS Treat?

IMS treats chronic pain conditions where muscle shortening, trigger points, and nerve hypersensitivity are the primary drivers of symptoms. IMS is most effective for pain that persists despite conventional treatment, particularly when there is no visible tissue damage on imaging but the patient continues to experience significant discomfort and restricted movement.

Conditions that respond well to IMS include chronic low back pain, chronic neck pain, whiplash-associated disorders, tension-type headaches, frozen shoulder, rotator cuff tendinitis, tennis elbow, golfer’s elbow, carpal tunnel syndrome, piriformis syndrome, sciatica, Achilles tendinopathy, chronic sprains and strains, temporomandibular joint (TMJ) dysfunction, and post-collision pain with delayed-onset symptoms. According to Dr. Gunn’s research, the most common underlying cause of these chronic pain patterns is spondylosis, which refers to degenerative changes in the spine from normal wear and tear. Spondylosis irritates spinal nerves, which causes the muscles those nerves control to shorten, tighten, and develop trigger points. IMS addresses this nerve-muscle dysfunction directly.

Myofascial pain syndrome (MPS) is the condition most closely associated with IMS treatment. Research published by IntechOpen reports that myofascial trigger points are found in up to 85% of patients presenting to pain clinics. These trigger points are palpable, tender knots within taut bands of muscle that produce local pain, referred pain, and restricted range of motion. Chiropractic care can complement IMS by addressing the spinal joint restrictions that contribute to the nerve irritation driving the muscle shortening in the first place.

Is IMS a Good Treatment for Sciatica?

Yes, IMS is a good treatment for sciatica when the sciatic pain is caused or worsened by muscle shortening and trigger points in the gluteal muscles, piriformis, hamstrings, or deep spinal muscles compressing the sciatic nerve. IMS releases the shortened muscles that are trapping or irritating the nerve, which reduces the compression and allows the nerve to function normally. IMS is not a substitute for medical evaluation of sciatica, because sciatic pain can also result from disc herniation, spinal stenosis, or other structural causes that require different treatment approaches. A thorough assessment by a physiotherapist determines whether IMS is appropriate for your specific presentation.

What Does IMS Feel Like?

IMS feels like a deep muscle cramp or dull ache when the needle reaches a trigger point, followed by a noticeable release of tension once the muscle relaxes. The sensation is brief, typically lasting only a few seconds per needle insertion, and most patients describe it as uncomfortable but tolerable rather than painful.

When the needle enters a muscle that does not contain a trigger point, you feel little to nothing. When the needle reaches a shortened, supersensitive muscle with an active trigger point, you feel the twitch response, which is the muscle contracting involuntarily around the needle. This twitch is what confirms that the needle has reached the target tissue. Patients often describe this moment as a deep cramp that releases almost immediately, followed by a sense of looseness in the area. Some practitioners describe the post-twitch sensation as the “release” moment where the muscle lets go of its chronic tension.

After the session, mild soreness and achiness in the treated area are normal and expected. This post-treatment soreness resembles the feeling after a hard workout at the gym and typically lasts 24 to 36 hours. The soreness results from the controlled micro-injury the needle creates and the muscle’s inflammatory healing response. Staying hydrated, moving gently, and applying heat to the treated area after your session helps reduce the duration and intensity of post-treatment soreness. Laser therapy can also accelerate tissue healing and reduce inflammation after needle-based treatments.

What Are the Side Effects of IMS Treatment?

The side effects of IMS treatment are generally mild and short-lived. The most common side effects are localised muscle soreness lasting 24 to 36 hours, minor bruising at the needle insertion site, and temporary fatigue.

Normal Post-IMS Reaction	Warning Sign That Needs Attention
Deep, dull muscle soreness for 24-36 hours	Sharp, worsening pain that does not fade within 48 hours
Small bruise at the needle site that fades in 2-3 days	Large, spreading, or painful bruising
Feeling tired or drowsy for a few hours after treatment	Dizziness, nausea, or fainting that persists
Temporary increase in muscle twitching	Numbness, tingling, or weakness in the treated limb
Mild redness at the needle site	Redness spreading with warmth, swelling, or fever (possible infection)

Sources: Leading Edge Physiotherapy, Institute for the Study and Treatment of Pain (iSTOP), Scientific Reports (2022)

Serious complications from IMS are extremely rare when the technique is performed by a trained, certified practitioner. The risk of pneumothorax (punctured lung) exists when needling near the rib cage, but proper training and technique eliminate this risk in clinical practice. Excessive bleeding is uncommon because the needles are extremely thin (0.25 mm diameter) and do not damage blood vessels the way a hypodermic needle would. Infection risk is negligible when practitioners follow clean needle technique with single-use sterile needles, skin disinfection, and gloves. Your practitioner should screen you for contraindications before performing IMS and explain the specific risks associated with the area being treated.

Who Should Not Do Dry Needling?

You should not do dry needling or IMS if you are pregnant (due to the risk of inducing labour), if you are taking blood-thinning medication at high doses, if you have an active infection in or near the treatment area, if you are immunocompromised, or if you have had surgery in the treatment area within the previous 12 weeks. These contraindications exist because the needle creates a controlled micro-injury that requires a normal healing response, and conditions that impair healing or increase bleeding risk make the treatment less safe.

Patients with a severe needle phobia may also be poor candidates for IMS, not because the treatment is dangerous but because extreme anxiety during the procedure can increase muscle guarding and reduce the effectiveness of the technique. Your physiotherapist will discuss your medical history, medications, and comfort level during the initial assessment before recommending IMS or any needle-based treatment. In some cases, exercise rehabilitation and manual therapy can achieve similar results for patients who cannot or prefer not to receive needling. Custom orthotics may also complement treatment by correcting biomechanical imbalances that contribute to chronic muscle tension in the lower body.

Does IMS Really Work?

Yes, IMS works for many patients with chronic musculoskeletal pain, particularly when the pain involves neuropathic components and myofascial trigger points. Research supports dry needling as an effective treatment for chronic pain, with multiple systematic reviews and randomised controlled trials demonstrating improvements in pain intensity, functional capacity, and range of motion.

A 2022 prospective, randomised, single-blinded study published in Scientific Reports found that dry needling significantly reduced pain intensity and improved functional efficiency in patients with chronic low back pain caused by L5-S1 disc disease. The improvements persisted at one-month and three-month follow-ups, while the control group receiving sham needling showed only short-term benefits that deteriorated over time. A systematic review and meta-analysis published in Pain Research and Management analysed 14 randomised clinical trials on dry needling for chronic neck pain and found that all included studies reported improvements in pain and disability, regardless of the specific protocol followed or muscles targeted. The review noted that dry needling was effective in both women and men with no significant adverse effects reported.

Dr. Gunn’s published research on IMS for low back pain found that the average number of treatments required was 8.2 sessions, and some patients treated with IMS remained pain-free for over 20 years. A systematic review from the Journal of Orthopaedic and Sports Physical Therapy evaluated 13 studies on trigger point dry needling for musculoskeletal conditions and reported a median methodological quality score of 7 out of 10 on the PEDro scale, indicating good-quality evidence. The effects of IMS are cumulative, meaning each session stimulates additional healing until the condition resolves.

IMS does not work for every patient or every type of pain. Pain caused by fractures, infections, tumours, or inflammatory conditions like rheumatoid arthritis requires different treatment. A proper assessment determines whether your pain pattern fits the neuropathic and myofascial profile that responds to IMS. Understanding physiotherapy benefits helps patients evaluate which treatment approach is right for their specific condition. Physiotherapy treatments that include exercise, manual therapy, and patient education work alongside IMS to address the full scope of the condition rather than relying on needling alone.

How Many IMS Sessions Do I Need?

The number of IMS sessions you need depends on how long you have had the condition, how much muscle shortening is present, and how quickly your body heals. Most patients notice improvement after the first session, with good results typically appearing after 3 to 4 sessions and full treatment courses averaging 8 to 10 sessions.

Treatments are typically scheduled once per week to allow the body enough time to heal between sessions. Pain that is more recent in origin may require fewer sessions, sometimes as few as one or two. Chronic conditions that have been present for months or years, or conditions involving significant scar tissue from previous surgery, generally require more sessions because the muscle shortening and nerve sensitisation are more deeply established. Younger patients tend to heal faster, though older patients also respond well when the treatment frequency and intensity are appropriate.

The rate of improvement is cumulative. Each session releases a certain amount of muscle tension, desensitises the involved nerves a little further, and adds another layer of healing to the treated tissue. If you are not experiencing any improvement after 3 sessions, your practitioner should reassess whether IMS is the right approach for your condition and consider alternative or complementary treatments.

What Should You Do After an IMS Session?

After an IMS session, you should drink plenty of water, stay gently active, and apply heat to the treated area to reduce post-treatment soreness. These aftercare steps support the healing response triggered by the needling and help the treated muscles recover faster.

1. Drink 2 to 3 extra glasses of water in the hours following your session. Hydration helps flush metabolic waste produced by the muscle’s inflammatory healing response and supports nutrient delivery to the treated tissue.
2. Keep moving gently. A short walk, light stretching, or easy activity prevents the treated muscles from stiffening up. Avoid intense exercise, heavy lifting, or high-impact activity for 24 to 48 hours after treatment.
3. Apply a warm towel, heating pad, or warm bath to the treated area for 15 to 20 minutes. Heat increases blood flow, relaxes the muscles further, and reduces the post-treatment achiness. Do not use ice after IMS unless your practitioner specifically instructs it, because ice constricts blood flow and can slow the healing response the treatment initiated.
4. Complete any exercises your physiotherapist prescribes. IMS releases the tight muscle, but exercise rebuilds the strength and movement patterns that prevent the muscle from shortening again. The combination of IMS and targeted exercise produces better long-term results than either treatment alone.

Post-treatment soreness should fade within 24 to 36 hours. Once the soreness subsides, you should feel looser, move more freely, and experience reduced pain in the treated area. If soreness persists beyond 48 hours or worsens instead of improving, contact your practitioner before your next session.

Is IMS Covered by Insurance in Canada?

Yes, IMS is covered by most extended health insurance plans in Canada when the treatment is performed by a registered physiotherapist. Because IMS is delivered as part of a physiotherapy session by a licensed physiotherapist, it falls under physiotherapy benefits on most private insurance plans. The treatment itself is not billed separately from physiotherapy; it is one of several techniques your physiotherapist may use during your session.

Coverage details vary by plan, so check with your insurance provider to confirm your physiotherapy benefit limits, per-session maximums, and whether a physician’s referral is required for reimbursement. In Ontario, physiotherapists are primary care practitioners, which means you can book directly without a referral from a family doctor. Some insurance plans still require a referral for reimbursement despite this, so verifying your specific policy before your first visit avoids surprises at the front desk. WSIB claims and motor vehicle accident insurance typically cover physiotherapy that includes IMS for patients recovering from workplace injuries or car accidents.

Frequently Asked Questions

Why Do I Feel Weird After Dry Needling?

You feel weird after dry needling because the treatment triggers a neurological and muscular response that your body is not accustomed to. The needle stimulates a reflex contraction and relaxation in muscles that have been chronically shortened, which can produce temporary sensations of heaviness, fatigue, light-headedness, or a “floaty” feeling. These sensations result from the nervous system recalibrating after the nerve desensitisation and muscle release. The feeling typically resolves within a few hours. Drinking water, eating a light meal, and resting briefly after your session helps your body settle.

How Long Does It Take to Fully Recover From Dry Needling?

Full recovery from the post-treatment soreness of a dry needling session takes 24 to 36 hours for most patients. The localised muscle ache peaks within the first 12 to 24 hours and fades by day two. Minor bruising may take 2 to 4 days to resolve. Full recovery from the underlying condition being treated depends on the number of sessions required, which averages 8 to 10 for chronic conditions. Each session builds on the previous one, so the cumulative benefit increases over the course of treatment.

What Should You Not Do After Dry Needling?

You should not do intense exercise, heavy lifting, or high-impact activity for 24 to 48 hours after dry needling. Avoid applying ice to the treated area unless specifically instructed, because ice constricts blood flow and can slow the healing response. Do not consume alcohol after your session, as alcohol increases inflammation and impairs tissue repair. Avoid prolonged sitting or immobility in the treated area, because gentle movement helps the released muscles recover faster and prevents them from tightening up again.

Can IMS Make Pain Worse Before It Gets Better?

Yes, IMS can make pain temporarily worse before it gets better. The post-treatment soreness from the controlled micro-injury and muscle twitch response can increase discomfort in the treated area for 24 to 36 hours. This temporary increase is a normal part of the healing process. The soreness should peak within the first day and then fade, leaving you with reduced pain and improved mobility compared to before the session. Pain that worsens beyond 48 hours or that feels different from the expected deep muscle ache should be reported to your practitioner.

Is IMS Safe for Older Adults?

Yes, IMS is safe for older adults when performed by a trained, certified practitioner who screens for contraindications. Age alone is not a barrier to receiving IMS. Older adults with chronic pain from osteoarthritis, spondylosis, or degenerative conditions often respond well to IMS because the technique directly addresses the nerve-driven muscle shortening that accompanies spinal degeneration. The practitioner adjusts needle depth, treatment intensity, and the number of trigger points addressed based on the patient’s overall health, tissue quality, and tolerance. Healing may take slightly longer in older patients, but the treatment remains effective.

What It All Comes Down To

IMS is a dry needling technique grounded in western neurophysiology that targets the nerve-muscle dysfunction behind chronic pain. It works by releasing shortened muscles through a reflex relaxation response, desensitising irritable nerves, and triggering a localised healing process. IMS treats conditions like chronic back and neck pain, whiplash, headaches, frozen shoulder, sciatica, and tennis elbow, particularly when those conditions have not responded to conventional treatment. The effects are cumulative, most patients improve within 3 to 4 sessions, and published research supports its effectiveness for chronic musculoskeletal pain.

If you are dealing with chronic pain that has not improved with other treatments, a physiotherapy assessment can determine whether IMS or a related needle-based technique like contemporary medical acupuncture is appropriate for your condition. At KC Rehab, our physiotherapists assess the full picture of your pain, identify the structures involved, and build a treatment plan using the techniques best suited to your body. Call us at 905-205-1668 to book your initial assessment.