IMS: An Effective Technique for Pain Relief, Improving Function & Injury Prevention

Introduction

This article is meant to provide education to current clients, future clients, or any other interested parties. It will provide a basic level of knowledge which is available in the current research and should help to answer your question including: "How does it work?", and "Why does my muscle twitch when you put a needle there?!"

Intramuscular Stimulation (IMS) is one of the most effective techniques available to reduce muscular pain and tightness; Essentially IMS 'resets' trigger points (TrPs) to allow for normal muscle contraction and relaxation. The technique is known by many names: IMS, GunnIMS, Dry Needling, Functional Dry Needling (FDN), Trigger Point Needling, and Intramuscular Manual Therapy. Regardless of the name, all methods use the same theory and should attain similar results, providing the diagnosis is correct and the practitioner is competent.

The most recent systematic review, published in 2015, analyzed 25 high-quality studies and found significant improvement in pain, range of motion, function and quality of life when IMS was used in multiple body regions (1).  Its reputation has become well-known: Many advocates from the medical and research community call IMS the most important contribution to pain science and treatment in the last 20 years.  As a result it has become a highly sought after skill-set in professional sport, chronic pain centers and physiotherapy clinics everywhere.
 
TrPs have been scientifically acknowledged since the early 1900s, when Sir William Gowers introduced the (now dated) term “fibrositis”, meaning a palpable tenderness and hardness of a muscle. Significant headway was made in the 1970s by Dr. Janet Travell (MD for Presidents Kennedy and Johnson) who authored research documenting TrP pain referral patterns.  However, it wasn’t until Dr. Chan Gunn introduced his theories and supporting research in the late 1990s that IMS started to gain formal recognition as a treatment modality.
 
Physiotherapists and physicians with specialized post-graduate training perform IMS. A thorough physical examination proves indispensable as chronic pain is neurologically driven (as opposed to structural), and therefore it is undetectable by X-rays, MRI Tests, Bone and CT Scans. If relevant TrPs are found on examination, a sterile acupuncture needle is then inserted and moved for 1-5 seconds in the tight muscle, causing a cramping or twitch response of the muscle.  Needles may also be inserted near the spine where nerve roots have become irritated and hypersensitive. 
 
Before we can examine the effects of IMS on TrPs, let's first identify what we know about them.

Three Types of Trigger Points

There are three types of trigger points:
 
Active Trigger Points – A hyperirritable spot in a taut band of skeletal muscle/fascia which is painful without being touched (but more painful with compression) and produces characteristic pain, referred symptoms, motor dysfunction and/or autonomic nervous system signs/symptoms.
 
Latent Trigger Points – A hyperirritable spot that is painful with compression, but does not have referral symptoms.
 
Satellite Trigger Points – A latent point that develops in a synergist muscle, antagonist muscle, muscle with common neural link or the same pain referral zone.  These trigger points may become symptomatic neurogenically or mechanically by an increased irritability of the key TrP.

Trigger Point Characteristics

Trigger points have been studied thoroughly in the research.  Here is what we know to date:

1. Muscles with TrPs have altered muscle activation patterns (2, 3).   
2. Active TrPs have decreased blood flow, and as a result they are ischemic (decreased muscle oxygen) (4, 5).
3. TrPs spontaneously depolarize, which creates electrical noise – measurable by EMG.  This is caused by Spontaneous Electrical Activity. It is similar to a healthy muscle contraction, muscle cramp potential (6), and correlates with increased pain on palpation (7).
4. TrPs can produce a local twitch response by stimulating them.  This is a local, reflex driven response of a dysfunctional muscle (8).
5. TrPs are visible on Real-Time Ultrasound as they are hypoechoic (absorb soundwaves more easily). Local twitch responses can also be seen on ultrasound (9).
6. TrPs are stiffer than surrounding tissue as measured by Magnetic Resonance Elastography (10). 
7. Through vibrational sonography, active TrPs are measured as larger than latent TrPs (4). 
8. Active TrPs have biochemical dysfunction:

           A) Elevated hydrogen ions (making the TrP acidic) (11-14).  
           B) Elevated neurotransmitters and neuropeptides involved in pain sensitivity, vasoconstriction,  vascular permeability, mast cell degranulation (mast cells release inflammatory components), increased sympathetic activity in motor endplate regions of TrP, decreased feedback control of muscle length and increased spontaneous electrical activity at motor endplates (14).
           C) Elevated cytokines and chemokines involved in inflammation, immune regulation, sensitivity of nociceptors and increased pain in the muscle (14).

Physiological Effects of IMS

As we insert an acupuncture needle into a TrP, a reset of the neuromuscular system occurs.  This results in reduced local and referred pain (15, 16), improved range of motion (2, 3) and decreased TrP irritability both locally (7, 17) and remotely (8, 18).  It is also proposed that these changes reduce associated dysfunction caused by the pulling effects of the tight muscles across joints, discs, nerves, tendons, etc.  These results occur for the following reasons:

1. Stretch receptors in the muscle are stimulated, producing a reflex relaxation (lengthening) via a spinal cord reflex.  This leads to decreased muscle banding by restoring normal sarcomere length to allow for improve efficiency of the contraction (8, 18).
2. The needle causes a small injury that draws blood to the area, initiating the natural healing process.  This increased blood flow lasts long after the needle is removed (19).  In contrast, applying heat to a muscle lasts only a few minutes after it is removed.
3. Typically acetylcholine is created and used to create a muscle contraction at the neuromuscular junction.  After it is depleted, the muscle stops contracting.  In TrPs there is a continued low-level of acetylcholine present at the neuromuscular junction, causing low grade, constant spasm.  Research points to a change in acetylcholine after the muscle twitch response from IMS; There is decreased spontaneous electrical activity and normalization of acetylcholine levels (7).
4. Many biochemical changes have been noted to occur at the tissue level including: Significant decreases in levels of Substance P and CGRP, increase in endorphin levels, and an increase in proteins responsible for growth of capillaries in the tissue (20).  This means that the pH of the muscle is lowered, and therefore it also lowers the irritability (12, 13).
5. Many changes have been noted to occur at the Central Nervous System level including: Changes in substance P levels in the dorsal root ganglion (12-14), decreased pain on palpation of muscles that are along the same myotome (16, 18), activation of the periaqueductal gray regions in the brain as seen on fMRI (involved in descending inhibition of pain) (21), and autonomic sympathetic changes that can be seen during treatment (sweating, goose-bumps, and circulatory change). 

Conclusion

IMS requires a medical examination and diagnosis by a practitioner knowledgeable in musculoskeletal pathology and human anatomy. The technique is supported by high-quality research, and when applied correctly, it can help provide lasting relief to patients with acute and chronic pain.

References

1) Boyles R, Fowler R, Ramsey D, Burrows E. Effectiveness of trigger point dry needling for multiple body regions: a systematic review. Journal of Manual and Manipulative Therapy. 2015 Jun 18:2042618615Y-0000000014.

2) Lucas KR, Rich PA, Polus BI. Muscle activation patterns in the scapular positioning muscles during loaded scapular plane elevation: the effects of latent myofascial trigger points. Clin Biomechanics. 2010;25(8):765-770.
 
3) Lucas KR, Polus BI, Rich PS. Latent myofascial trigger points: their effects on muscle activation and movement efficiency. J Bodyw Mov Ther. 2004;8:160-166.
 
4) Ballyns JJ, Shah JP, Hammond J, Gebreab T, Gerber LH, Sikdar S. Objective sonographic measures for characterizing myofascial trigger points associated with cervical pain. J Ultrasound Med. Oct 2011;30(10):1331-1340.
 
5) Brückle W, Sückfull M, Fleckenstein W, Weiss C, Müller W. Gewebe-pO2-Messung in der verspannten Rückenmuskulatur (m. erector spinae). Z. Rheumatol. 1990;49:208-216.
 
6) Ge HY, Fernandez-de-Las-Penas C, Yue SW. Myofascial trigger points: spontaneous electrical activity and its consequences for pain induction and propagation. Chin Med. 2011 Mar 25;6(13):1-7.
 
7) Kuan TS, Hsieh YL, Chen SM, Chen JT, Yen WC, Hong CZ. The myofascial trigger point region: correlation between the degree of irritability and the prevalence of endplate noise. Am J Phys Med Rehabil. 2007;86(3):183-189.

8) Hsieh YL, Chou LW, Joe YS, Hong CZ. Spinal cord mechanism involving the remote effects of dry needling on the irritability of myofascial trigger spots in rabbit skeletal muscle. Arch Phys Med Rehabil. Jul 2011;92(7): 1098-1105.

9) Rha DW, Shin JC, Kim YK, Jung JH, Kim YU, Lee SC. Detecting local twitch responses of myofascial trigger points in the lower-back muscles using ultrasonography. Archives of physical medicine and rehabilitation. 2011 Oct 31;92(10):1576-80.
 
10) Chen Q, Bensamoun S, Basford JR, Thompson JM, An KN. Identification and quantification of myofascial taut bands with magnetic resonance elastography. Archives of physical medicine and rehabilitation. 2007 Dec 31;88(12):1658-61.
 
11) Shah JP, Danoff JV, Desai MJ, et al. Biochemicals associated with pain and inflammation are elevated in sites near to and remote from active myofascial trigger points. Arch Phys Med Rehabil. Jan 2008;89(1):16-23.

12) Shah JP, Gilliams EA. Uncovering the biochemical milieu of myofascial trigger points using in vivo microdialysis: an application of muscle pain concepts to myofascial pain syndrome. J Bodyw Mov Ther. Oct 2008;12(4):371-384.

13) Shah J, Phillips T, Danoff JV, Gerber LH. A novel microanalytical technique for assaying soft tissue demonstrates significant quantitative biomechanical differences in 3 clinically distinct groups: normal, latent and active. Arch Phys Med Rehabil. 2003;84:A4.
 
14) Shah JP, Phillips TM, Danoff JV, Gerber LH. An in vivo microanalytical technique for measuring the local biochemical milieu of human skeletal muscle. Journal of applied physiology. 2005 Nov 1;99(5):1977-84.

15) Affaitati G, Costantini R, Fabrizio A, Lapenna D, Tafuri E, Giamberardino MA.  Effects of treatment of peripheral pain generators in fibromyalgia patients. Eur J Pain. Jan 2011;15(1): 61-69.

16) Srbely JZ, Dickey JP, Lee D, Lowerison M. Dry needle stimulation of myofascial trigger points evokes segmental anti-nociceptive effects. J Rehabil Med. 20110;42(5):463-468.

17) Chen JT, Chung KC, Hou CR, Kuan TS, Chen SM, Hong CZ. Inhibitory effect of dry needling on the spontaneous electrical activity recorded from myofascial trigger spots of rabbit skeletal muscle. Am J Phys Med Rehabil. Oct 2001;80(10):729-735.
 
18)Tsai C-T, Hsieh L-F, Kuan T-S, Kao M-J, Chou L-W, Hong C-Z. Remote effects of dry needling on the irritability of the myofascial trigger point in the upper trapezius muscle. Am J Phys Med Rehabil. 2010;89(2):133-140.

19) Cagnie B, Barbe T, De Ridder E, Van Oosterwijck J, Cools A, Danneels L. The influence of dry needling of the trapezius muscle on muscle blood flow and oxygenation. Journal of manipulative and physiological therapeutics. 2012 Dec 31;35(9):685-91.

20) Hsieh YL, Yang SA, Yang CC, Chou LW. Dry needling at myofascial trigger spots of rabbit skeletal muscles modulates the biochemicals associated with pain, inflammation, and hypoxia. Evidence-based complementary and alternative medicine. 2012 Dec 23;2012.

21) Niddam DM, Chan RC, Lee SH, Yeh TC, Hsieh JC. Central modulation of pain evoked from myofascial trigger point. The Clinical journal of pain. 2007 Jun 1;23(5):440-8.