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devices for thermoception. Interestingly, in fascial tissues, most of the interstitial (between fibrous tissue) neurons are so- called polymodal receptors, meaning they are responsive to more than one kind of stimulation. There are four types of specialized proprioceptive mechanoreceptors in fascia: Golgi, Pacini, Ruffini, and muscle spindle receptors. 11 Golgi Receptors Golgi endings are slowly adapting receptors that respond to tensional loading. While they were previously assumed to be present only in tendinous tissues, their existence in other fascial tissues has been repeatedly confirmed by several independent investigators. 12 Their presence is particularly enriched in the myotendinous junctions and close to the intermuscular septa. Stimulation of Golgi receptors tends to trigger a relaxation response not in the whole body, but only in those skeletal muscle fibers which are directly linked with the respectively tensioned collagen fibers. Nevertheless, if tendinous extramuscular tissues are stretched "in series" (i.e., in contrast to a parallel alignment) with muscle fibers that are in a relaxed condition, then most of the respective elongation will be "swallowed" by the more compliant myofibers. In this way, the respective stretching impulse may not provide sufficient stimulation for eliciting any muscular tonus change. 13 A practical conclusion of this may be that a stretching impulse, aimed at reaching the tendinous tissues, may benefit from including some moments in which the lengthened muscle fibers are actively contracting or are temporarily resisting their overall elongation. In addition, a manual approach in which the fascial tissues are stretch-loaded in a direction orthogonal to the direction of closest myofibers (as is frequently practiced in manual cross-fiber techniques based on the teaching of Tim Bowen), it could well be that sufficient elongation can be achieved in the passively lengthened collagenous fibers, despite the more compliant myofibers in their vicinity. Pacini Receptors The Pacini receptors are rapidly adapting and therefore tend to stop responding to a continuous stimulus. In contrast, they are very sensitive to dynamic changes in mechanical stimulation. Gentle rocking, as well as more rapid vibratory stimulation, appears to be a suitable stimulation method for these receptors. Such treatment could therefore have beneficial effects on proprioception. Ruffi ni Receptors Ruffini receptors are slowly adapting, and tend to remain sensitive in response to a continuous stimulus. They can monitor longer-lasting postural sensations, as well as slowly melting myofascial manipulation techniques. In addition, they are highly sensitive to differences in directional shear loading, which may correspond to the "local listening" approach used by many osteopaths when they use their hands to detect the specific direction a given tissue "wants to move." Muscle Spindle Receptors The muscle spindle receptor is a fusiform specialized mechanoreceptor. It includes several intrafusal muscular fibers and is surrounded by a strong capsule of connective tissue. 14 While it did not exist in our early evolutionary fish ancestors, it is particularly expressed in muscular regions with a strong antigravity regulation function. Combined with the recent 2021 Nobel Prize in Physiology or Medicine that was surprisingly dedicated to sensory receptors in the human body, increasing attention is currently placed on the newly discovered PIEZO2 membrane receptors on the surface of human muscle spindles. These tiny membrane receptors, several magnitudes smaller than the spindle itself, are highly sensitive to mechanical stimulation and play an important role in proprioception. Associated with genetic variations in our population, it was found that a high proportion of people with adolescent idiopathic scoliosis are characterized by a diminished expression of these PIEZO2 receptors in their muscular tissues and by a related impaired proprioception. For many therapists and researchers dealing with scoliosis, even more exciting was the discovery that these persons express much smaller muscle spindles compared to healthy non-scoliotic persons. 15 Spindle capsules are usually embedded into the intramuscular fascial layer of the perimysium. Since muscle spindles can detect tensional differences of just 3 grams, it is assumed their sensitivity can be significantly impaired by increased stiffness of the surrounding perimysium. 16 Such stiffness is frequently associated with chronic immobilization and with many fibrotic pathologies. Such tissue changes may therefore result in impairments of proprioceptive refinement comparable to those associated with genetically associated spindle differences in adolescent idiopathic scoliosis. FASCIA AS A PAIN ORIGINATOR Most studies about fascial nociception have been directed at the thoracolumbar fascia (or lumbar fascia in some animals). Based on these, it is known that this fascia is densely innervated and its free nerve endings can provide nociceptive signaling to dorsal horn neurons in the spinal cord. 17 Interestingly, it was shown that stimulation of this fascia (e.g., via injection of saline solution as a mild irritating substance) triggers stronger and longer-lasting pain sensations compared to stimulation of the muscles underneath. 18 Such fascial pain was experienced by the patients as burning, throbbing, and stinging. The decreased pain threshold in muscular tissues after intense exercise— described in sports medicine as delayed L i s te n to T h e A B M P Po d c a s t a t a b m p.co m /p o d c a s t s o r w h e reve r yo u a cce s s yo u r favo r i te p o d c a s t s 43