Understanding the basic physiological mechanisms of dry needling is of the most fundamental importance to the practitioner. These mechanisms underlie the actual process of stimulation by needles, and how such stimulation brings about therapeutic effects.
Needling is both a physical disturbance to soft tissue and a minute biological traumatic inoculation into soft tissue. The physical movement and manipulation of the needles in deep tissues increases the tension of the muscle fibers and connective tissue and creates the effect of mechanical signal transduction, which leads to self-healing.
A minute traumatic lesion and the lesion-induced inflammation remain in the tissue when the needle is removed. The diameter of a skeletal muscle fiber is 50 mm and the average diameter of the dry needles used in clinical practice is about 250 mm (gauges 32-36). Therefore if a needle is inserted into a muscle, perpendicularly to the fibers and to a depth of 1 cm, it may break at least 1,000 muscle fibers. If the needle is inserted deeper into the muscle, with manipulation, tens of thousands of muscle fibers as well as some capillaries and nerve endings may be broken or injured by it.
The brain identifies the traumatic lesion in the soft tissue and directs biological systems, including the cardiovascular, immune and endocrine systems, to replace the damaged tissue with the same type of fresh tissue within a few days. In this way self-healing starts in the needling location. In addition to this local healing effect, the lesion induces systemic effects to restore homeostasis through a number of reflex processes at different levels of the central nervous system.
It should be emphasized that dry needling, as a nonpharmaceutical modality, promotes self-healing by reducing the mechanical and biological stress of the body. Some patients with soft-tissue pain will achieve self-healing without any medical intervention after a sufficient period of time. Nevertheless, dry needling accelerates this self-healing process and reduces unnecessary suffering. This acceleration also helps to prevent the development of chronic pathology. Without this understanding there is a potential for confusion. For example, a recent study showed that in the first 10 weeks of treatment, a needling-treated group experienced a much higher level of improvement (4.4 points) than a group treated with conventional methods (2.1 points). After 52 weeks, however, there was little difference between the group treated with needling and the control group. 8 This result is objective and can be correctly interpreted if the physiological nature of needling therapy is understood: both groups achieved self-healing by the end of the research period (52 weeks), but the group treated with needling suffered much less and had less potential for developing chronic pain than the control group. This is the clinical value of dry needling therapy.
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