There are five physiological mechanisms which can be used to explain how medical acupuncture works. Each can be used for a different purpose which is why anyone using medical acupuncture must be able to make a conventional medical diagnosis and have an understanding of the underlying pathology to be effective when using a medical approach.
The different mechanisms require variations in the treatment technique and so this needs to be tailored to the individual patient.
This refers to the ability of acupuncture to activate specific sensory nerve fibres in the skin and muscle. Needling near the sensory nerve endings sets off action potentials (nerve impulses) which spread around and along the local network of nerve fibres – this is called an axon reflex. Various substances are released as a result including adenosine and calcitonin gene related peptide (CGRP) both of which cause local blood vessels to dilate causing an increase in local blood flow. The blood flow is also increased in the deeper tissues which encourages tissue healing. Adenosine also has a mild local pain relieving effect effect, while CGRP may also promote healing and repair.
Summary: Acupuncture promotes local healing in the tissues.
The action potentials which have been generated by the insertion of the needle also travel along the nerve directly to its particular segment (entry point) in the spinal cord where it causes a depression in activity at the dorsal horn which reduces its response to painful stimuli. This is called the ‘segmental effect’ of acupuncture and is most likely the main mechanism by which acupuncture is able to relieve pain. Acupuncture is capable of inhibiting pain signals arising from any structure which sends sensory nerves to that particular part (segment) of the spinal cord. A good example is pain arising from an arthritic knee. The nerves from the painful knee enter the spinal cord at the same segments in the spinal cord as the muscles around the knee. As such, by inserting needles into the muscles around the knee it is possible to inhibit pain arising from the knee itself.
In addition to segmental pain relieving effects, the insertion of a needle may also reduce muscle tension more generally within the area being needled (mainly within the same spinal segments) which may improve muscle function as well as joint mobility.
Summary: Inserting a needle into, or near a painful structure may bring about strong pain relieving effects as well as modulation of muscle tone and autonomic activity within segmentally related tissue.
The action potentials which having occurred due to the needle stimulating the nerves in the muscle and skin then travel up the spinal cord to the brainstem where they stimulate the body’s own pain suppressing mechanisms by activating the hypothalamus which releases beta endorphin. Beta endorphin also causes part of the brainstem to release the neurotransmitters serotonin and noradrenaline which travel along nerves which descend back down the spinal cord and inhibit pain signals entering the spinal cord from all over the body.
In this way acupuncture can have an all over body effect in terms of relieving pain. This effect is most likely not dependant on where the needle is inserted, but large muscles are generally a good option. This effect is called extra- segmental analgesia and although not the most powerful, does help the overall effect of acupuncture.
Summary: Inserting a needle anywhere in the body will bring about some pain relieving effects.
Central regulatory effects:
Once the action potentials have passed through the midbrain, they then pass to other area of the brain. One of these is the somatosensory cortex which processes sensory information and registers the needle sensation which is usually felt as a deep, dull, ache, numbness or tingly feeling. It is not meant to be aversively painful, if it is the needle should be removed as it is less likely to have a therapeutic effect.
The action potentials then go on to influence other parts of the brain. One of these is the limbic system which is the emotional centre of the brain. This may explain why acupuncture has a calming effect and improves a sense of wellbeing. Clients report feeling more cheerful and more motivated with a more positive outlook on life. It is important to recognise that this effect may also be influenced by other aspects of the therapeutic relationship with the practitioner.
Another part of the brain which is influenced by acupuncture is the hypothalamus, otherwise known as the ‘central regulator’ due to its role in controlling a number of body functions. As such acupuncture may, due to its effects on the hypothalamus:
- Regulate the autonomic nervous system which controls automatic body processes such as blood vessel constriction and dilation, heart rate and blood pressure.
- Regulate various hormones, such as those female hormones which control the menstrual cycle.
Summary: Acupuncture has a calming effect and improves well being.
Myofascial Trigger Points:
When a muscle is overworked or overloaded, put in a position of stress for a prolonged period of time, or strained due to an awkward movement it can develop a small area of injury which can be slow to heal and go on to cause persistent pain and dysfunction.
These small knots which develop within taut bands of muscle are called Myofascial Trigger Points (MTrP). These MTrP’s are not fully understood however it is essential they are identified and treated otherwise they may go on to cause persistent pain.
Unfortunately most therapists and doctors, including those in the medical profession view injuries to muscle as less serious and just expect them to heal. This does not always occur and it takes an experienced clinician to identify the MTrP’s and treat them effectively. One of the simplest and most effective ways to treat these MTrP’s is to use acupuncture – when used in this way the technique is often referred to as ‘Dry Needling’
Summary: MTrP’s are often a cause of continued pain after an injury, it is important to identify and treat them and acupuncture/ dry needling is an effective method.
White A, Cummings M. Filshie J. An introduction to western medical acupuncture. Churchill Livingstone; 2008.
Campbell A. Acupuncture in practice: beyond points and meridians. Butterworth-Heinemann, Oxford; 2001.
Baldry PE. Acupuncture, trigger points and musculoskeletal pain. 3rd ed. Edinburgh: Elsevier Churchill Livingstone; 2005.
Andersson S, Lundeberg T. Acupuncture - from empiricism to science: functional background to acupuncture effects in pain and disease. Medical Hypotheses 1995; 45(3):271-281
Simons DG, Travell JG, Simons PT. Travell & Simons’ myofascial pain & dysfunction. The trigger point manual. Volume 1. Upper Half of Body. 2nd ed. Baltimore: Williams & Wilkins; 1999.
Lund I, Lundeberg T. Are minimal, superficial or sham acupuncture procedures acceptable as inert or placebo controls? Acupunct Med. 2006;24(1):13-15.
Bowsher D. Mechanisms of acupuncture. In: Filshie J, White A, editors. Medical acupuncture- a western scientific approach. 1st ed. Edinburgh: Churchill Livingstone; 1998.p.69-82.
Staud R, Price DD. Mechanisms of acupuncture analgesia for clinical and experimental pain. Expert Rev Neurother 2006;6:661–7.
Sandberg M, Lundeberg T, Lindberg LG, et al. Effects of acupuncture on skin and muscle blood flow in healthy subjects. Eur J Appl Physiol 2003;90:114–9.