By Cody McBeath
As acupuncture has emerged into mainstream medicine as a treatment option for a wide variety of conditions and disorders, it has garnered a great deal of attention from the western medical community. Curiosity, investigation, and scientific inquiry into this ancient modality has steadily increased ever since New York Times reporter James Reston received pain relief after an appendectomy during President Nixon’s visit to China in the early 1970’s (1). Since this time, many theories have been proposed as to the exact physiological mechanisms behind acupuncture’s efficacy. Thus, as scientific inquiry and controlled studies steadily increase, so to have the mechanisms of acupuncture become clearer. What has been found is that acupuncture has three main effects: it restores homeostasis, it reduces inflammation, and it relieves pain. The scope of this article is to look at five theories that have been proposed and review in brief detail the mechanism’s behind how acupuncture works.
Neurotransmitter & Endorphin Theory
Acupuncture needle insertion stimulates the release of specific neurotransmitters, such as serotonin, norepinephrine & GABA, and endogenous opioids, such as endorphins and enkephalins. It has been proposed that the release of these neurotransmitters and endogenous opioids lead to the analgesic, pain reducing, mood improving qualities often experienced during acupuncture sessions. Studies have shown that the use of low frequency electro-acupuncture leads to an increased release of endorphins and enkephalins that act to block our perception of pain and relieve stress (2).
Gate Control Theory
Acupuncture regulates our pain physiology system. We have two types of pain receptors (A- fibers & C- fibers) that carry pain signals to our spinal cord and central nervous system. Needle stimulation may inhibit the transmission of pain signals from A- fibers during acupuncture treatment. The basis of this theory is rooted in competition of pain signaling to the brain. Thus, when acupuncture activates receptors at a distal point on the body, these other pain- signaling mechanisms are “gated out” and unable to elicit a pain response (3,4).
Circulatory/Blood Chemistry Theory
Acupuncture affects the circulatory system by dilating the blood vessels through nitric oxide release, ultimately increasing blood flow and oxygenation to local tissues and muscles. The insertion of needles creates a “micro-trauma” to the body that increases the amount and migration of white blood cells to the area that helps improve immune function, removes metabolic waste, and reduces inflammation in the local area. As blood flow is increased, more nutrients and inflammatory mediators are circulating which leads to a faster healing response time after injury (5).
Growth Control Theory
It is believed that acupuncture points have a high correlation to areas on the body known as organizing centers that form during our embryonic development. Further, it has been shown that acu-points are areas where there is a high level of electrical conductivity as opposed to adjacent tissue. So, by stimulating acupuncture points we are regulating this growth control system of the body that is responsible for cellular and tissue growth and regeneration (6).
Connective Tissue Model
While the previous theories represented biological models of acupuncture, this theory presents a biomechanical mechanism of acupuncture. This model looks at the interaction between the muscles, connective tissue, and fascia and the acupuncture needle. By stimulating what are known as trigger points (taut bands of connective tissue) or the muscle spindle (innervation into muscle belly), acupuncture can release these tight bands of tissue and re-establish proprioceptive communication between the muscle and the central nervous system. When the strands of fascia wrap around the needle, leading to what’s called tissue-needle coupling, the body elicits a response to allow these areas to relax (7,8).