What is this strange feeling?
In terms of (western) physiology, it usually follows from the stimulation of a certain kind of nerve. There are two kinds of nerves in our skin and muscle, motor nerves and sensory nerves. Motor nerves are responsible for messages going outwards from the central nervous system to the muscles, telling them to contract when we want to move. The other kind are called sensory nerves, and these send information inwards from the skin and muscle telling us something about what we are feeling and touching. Painful and pleasant feelings, sensations of touch and temperature, travel along these sensory nerves.
There are different types of sensory nerve, and the dull ache of acupuncture seems to arise when sensory nerves called A-delta nerves in the skin, and type II/III in the muscles, are stimulated by acupuncture needles.
When these nerves are stimulated, as well as our feeling that dull ache, several other things happen. One of these is the release into the area around the nerve of a number of chemicals called neuropeptides, some of which cause an increase in blood flow into the area, and even perhaps the formation of tiny new blood vessels there. This is of course useful if, for example, the area has been damaged, as an increase in blood flow will allow the body’s healing mechanisms to be more effective. This local increase in blood flow is just one of the ways acupuncture promotes healing.
Another result of stimulating the A-delta or II/III nerves occurs where these nerves join the spinal cord, and involves the production there of a substance called encephalin, which serves to block transmission of painful signals from that part of the spinal cord. This means that, in effect, the dull achy feeling occurs at the expense of any sharp painful feelings, which are as it were drowned out. These sharp painful feelings make it to the spinal cord, but they do not get as far as the brain – so we don’t feel them. This is one of the mechanisms which explain how acupuncture can be used for pain relief.
So for these and other reasons, that dull achy feeling is a good thing. It shows that treatment is stimulating the A-delta and II/III nerves, and setting in train a number of therapeutic effects.
In the theory behind traditional acupuncture, the dull achy feeling is associated with something called ‘deqi’ (pronounced de-chee). Deqi occurs when the patient’s Qi ‘arrives’ at the needle, or is ‘grasped’ by the needle. As such it is a sign that the needle is in the right place and is starting to have a therapeutic effect. Sometimes the acupuncturist themselves can tell that deqi has arrived by being sensitive to what he or she feels when the needle is inserted; typically deqi feels like a fish biting on a line as the patient’s Qi grabs the needle.
Sometimes only a very faint sensation experienced by the patient, or a quite subtle something felt by the acupuncturist is all that is needed. At other times stronger ‘deqi’ may be required, and the needle may be rotated or otherwise manipulated so that a good strong dull tingle or ache arrives. In general, the more sensitive the patient – both physically and emotionally – the more subtle the deqi required.