As dry needlers, the implication is usually that we are targeting muscle tissue, more specifically trigger points within taut bands of muscle. Typical dry needling involves an axial lift and thrust type technique where the needle is near fully withdrawn and reinserted at and angle of about 20-30 degrees off the vertical in different directions. The aim with this more vigourous approach is to locate the trigger point and elicit a local twitch response, thought to be key to the therapeutic effect of needling. Rotating the needle while within the muscular taut band or trigger point is also taught on dry needling courses as a method of direct, local stretching.
There are other ways to approach needling trigger points which may be more superficial but usually still penetrating the muscle tissue. Baldry (2005) would describe 'leaving the needle in situ for some time but also intermittently twirling it' as a way of progressing treatment should short duration, superficial needling with no added stimulation be insufficient to elicit the desired clinical effects.
This technique of twirling or rotating either in a uni-or bidirectional manner is also commonly used as a method of providing added stimulation in more traditional approaches to Acupuncture.
Much has been written with regards the proposed physiological mechanisms of stimulating muscle tissue while needling. I recently wrote a 3 part blog discussing the sensory and motor effects of needling trigger point sites and the proposed therapeutic benefits.
But what effects could the needle be eliciting when passing through the subcutaneous loose ‘areolar’ as well as deeper intermuscular connective tissue fascial layers en route to the muscle tissue, in particular when a twirling or rotating technique is used to further stimulate the needles?
Langevin et al (2002) have investigated the effects and tell us that when needles are rotated, collagen bundles within the connective tissue adhere to the needle and wind around its shaft, creating a small ‘whorl’ of collagen in the immediate vicinity of the needle. Connective tissue effectively follows the rotating needle which then adheres to itself increasing the mechanical bond between the needle and the tissue. This form of needle manipulation effectively results in a pulling and gathering of connective tissue form the periphery resulting in a unique form of internal tissue stretching. This can be increased with further uni or bidirectional rotation movements such that tissue displacement several centimetres away from the needle may occur. This is sustained while the needle is left in situ.
The clinical effects of this internal stretching response are not as yet fully understood. It may result in visco-elastic reorganisation causing relaxation and improved mobility of the connective tissue as has been observed during passive stretching of connective tissue for sustained periods of time.
In addition animal experiments have confirmed an active fibroblastic response to needling where fibroblasts expand, flatten and increase their cross sectional area up to several cm away from the needle (Langevin et al, 2006). Again similar responses have been shown during sustained static stretching for at least 10 minutes resulting in further decreases in tissue tension (Langevin et al, 2011). We could postulate that this fibroblastic effect in response to needling may have further effects in connective tissue relaxation and be used to facilitate or augment tissue mobilisation perhaps.
It may also be the case that the winding of collagen around the needle during rotational stimulation has further sensory mechanical signalling effects, contributing to input provided by the muscular receptors to central nervous system as part of the needling effect.This hypothesis is supported by a study where the injection of collagenase, which breaks down collagen fibres, abolished the analgesic effect of needling in rats (Yu et al, 2009).
Given the close functional interaction between the fascial connective tissue binding and overlying muscle tissue, it seems likely that the effects of needling fascia are likely to influence the function of muscle and with it trigger points. Further research is needed to gain a better understanding of this interaction and with it the effects of needling these structures.
In the meantime we’ll have to be content with relieving pain and restoring function with our dry needling and perhaps over time we’ll gain further insight into the mechanisms which explain this remarkably effective form of therapy.