Fascia as an organ of communication

The previous section of this textbook demonstrated the topographical continuity as well as the specialized local adaptations of the global fascial network. Agreed, it is possible to dissect this continuous network into hundreds of different sheets and bundles, provided one is sufficiently talented in working with a surgical scalpel and given one has a clearly depicted guideline on where to place the cuts. However, when left without a dissection manual and looking at the tissue alone, it becomes apparent that all of those whitish collagenous membranes and envelopes seem to act together as one interconnected fibrous network. Nevertheless, for decades, ligaments, joint capsules, and other dense fascial tissues have been regarded as mostly inert tissues and have primarily been considered for their mechanical properties.

Already during the 1990s advances were being made in recognizing the proprioceptive nature of ligaments, which subsequently influenced the guidelines for knee and other joint injury surgeries (Johansson et al. 1991). Similarly, the plantar fascia has been shown to contribute to the sensorimotor regulation of postural control in standing (Erdemir & Piazza 2004).

This chapter will explore the potential of the fascial network as one of our richest sensory organs. Given the right stature, the overall mass and volume may be bigger than that of the fascial body. However, the surface area of the many million endomysial sacs and other membranous pockets endows this network with a total surface area that by far surpasses that of the skin or any other body tissue. Interestingly, compared with muscular tissue’s innervation with muscle spindles, the fascial network possesses a ten times higher quantity of sensory nerve receptors than its red muscular counterpart (van der Wal 2009). This includes many different types of sensory receptors, including the usually myelinated proprioceptive endings (Golgi, Paccini, and Ruffini endings), but also a myriad of tiny unmyelinated ‘free’ nerve endings, which are found almost everywhere in fascial tissues, but particularly in periosteum, in endomysial and perimysial layers, and in visceral connective tissues. If one includes these smaller fascial nerve endings in the calculation, then the amount of fascial receptors may possibly be equal or even superior to that of the retina, so far considered as the richest sensory human organ (Mitchell & Schmidt 1977). However, for the sensorial relationship with our own body – whether it consists of pure proprioception, nociception or the more visceral interoception – fascia provides definitely our most important perceptual organ (Schleip 2003).

Many years ago, the author was involved in a dispute between instructors of the Feldenkrais Method of somatic education (Buchanan & Ulrich 2001) and teachers of the Rolfing Method of Structural Integration (Jones 2004). Advocates of the second group had claimed that many postural restrictions are due to pure mechanical adhesions and restrictions within the fascial network, whereas the leading figures of the first group suggested that “it’s all in the brain”, i.e., that most restrictions are due to dysfunctions in sensorimotor regulation. In support of the sensorial hypothesis they cited the vividly published report of Trager (Trager et al. 1987; Juhan 1998), who had observed the disappearance of many muscular restrictions during general anesthesia in many of his patients. Subsequently, a small experiment was set up involving several representatives of those two schools, in which three patients undergoing orthopedic surgery gave their consent for having their range of motion tested (in passive arm elevation, as well as foot dorsiflexion) in the surgical theater immediately before and after commencement of general anesthesia. Given the limited scientific rigor of this preliminary investigation, the result nevertheless was convincing to all involved; most of the previously detected restrictions appeared to be significantly improved (if not absent) during the conditions of anesthesia. It seemed that what had been perceived as mechanical tissue fixation may at least be partially due to neuromuscular regulation.

The ongoing interdisciplinary dispute after this event led to a rethinking of traditional concepts of myofascial therapies, and several years later a first neurologically oriented model was published as a proposed explanatory model for the effects of myofascial manipulation (Cottingham 1985), later copied and expanded by many others in the field (Chaitow & DeLany 2000; Schleip 2003).

While fascial stretch therapies and manual fascial therapies often seem to have positive effects on palpatory tissue stiffness as well as on passive joint mobility, it is still unclear which exact physiological processes may be underlying these responses. Some of the potential mechanisms will be addressed in the clinical section of this book (Chapters 7.1–7.24); they may be due to dynamic changes in water content of the ground substance, to altered link proteins in the matrix, to an altered activity of fascial fibroblasts, as well as other factors. However, today an increasing number of practitioners are basing their concepts to some exten on the mechanosensory nature of the fascial net and its assumed ability to respond to skillful stimulation of its various sensory receptors.

The question then is: what do we really know about the sensory capacity of fascia? And what specific physiological responses can we expect to elicit in response to stimulation of various fascial receptors?

This second section of our textbook will explore some of these intriguing questions. The first chapter in this section will be of particular interest, as it gives a solid overview on what is currently known on the importance of fascial tissues for our sense of proprioception. While, in the past, much emphasis was placed on joint receptors (being located in joint capsules and associated ligaments), more recent investigations indicate that more superficially placed mechanoreceptors, particularly in the transitional area between the fascia profunda and the fascia superficialis, seem to be endowed with an exceptionally rich density of proprioceptive nerve endings (Stecco et al. 2008). While this may be relevant for the practice (and often profound beneficial effects) of skin taping in sports medicine – as well as for other therapeutic fields – further research is necessary to confirm whether the innervation of this superficial fascial layer does indeed play a leading role in proprioceptive regulation.

The sensory nature of fascia includes also its potential for nociception. The chapter on this perspective is written by leading experts in that field, all from Heidelberg University. They summarize their recent years of research about the nociceptive potential of the lumbar fascia. Their choice of the lumbar fascia as field of inquiry is, of course, not accidental. While some cases of low back pain are definitely caused by deformations of spinal discs, several large magnetic resonance imaging studies clearly revealed that for the majority of low back pain cases the origin may have to be searched for elsewhere in the body, as the discal alterations are often purely incidental (Jensen et al. 1994; Sheehan 2010). Based on this background, a new hypothetical explanation model for low back pain was proposed by Panjabi (2006) and subsequently elaborated on by others (Langevin & Sherman 2007; Schleip et al. 2007). According to these authors, microinjuries in lumbar connective tissues may lead to nociceptive signaling and further downstream effects associated with low back pain. The new findings from the Heidelberg group – reported in the next chapters – concerning the nociceptive potential of the lumbar fascia, therefore promise to have potentially huge implications for the diagnosis and treatment of low back pain. As this is a newly emerging field, their research will definitely trigger further research investigations into this important (and very costly) field within modern health care.

Two other chapters will complete this section. One will cover the newly rediscovered field of fascial interoception, which relates to mostly subconscious signaling from free nerve endings in the body’s viscera – as well as other tissues – informing the brain about the physiological state of the body. While sensations from proprioceptive receptors are usually projected via the somatomotor cortex, signaling from interoceptive endings is processed via the insula region in the brain, and is often associated with an emotional or motivational component. This field also promises interesting implications for the understanding and treatment of disorders with a somatoemotional component, such as irritable bowel syndrome or essential hypertension.

Finally, this section includes inspiring perspectives on neural communication dynamics within the fascial network. We invite the reader to read these pages with an open-minded attitude, although some of the potential mechanisms presented there appear to be of a hypothetical nature. However, it would certainly not be the first time within the fascinating field of fascia research that a hypothesis previously considered daring might lead to new and substantial insights with clear clinical applications.