OVERVIEW OF CONTEMPORARY STATE OF KNOWLEDGE REGARDING THE FASCIAL SYSTEM FROM MICRO LEVEL (MOLECULAR AND CELLULAR RESPONSES) TO THE MACROLEVEL (MECHANICAL PROPERTIES)
Within skeletal muscle, myofilaments connect to the laminar structures by Z-lines and costameres which develop a “molecular chain” between cellular components and extracellular matrix (ECM) molecules. This allows force transmission that regulates local fascia.
Aging, characterized by chronic low-grade inflammation in the ECM, creates densification and fibrosis within fascia which creates mechanical consequences. Exercise can systemically regulate tissue by excreting circulatory molecules and in addition, the ECM can create a barrier for immune cells which limits inflammation which is beneficial for tissue regeneration.
Non-myotendinous pathways along mysial elements are thought to be partly dependent on myofascial tissue linkages. Stiff myofascial tissue, through changes in fluid content, molecular crosslinking, content of ECM molecules, contractile activity of myofibroblasts, muscle injury, disease, surgery or age influence the magnitude of intermuscular force transmission.
As fascial tissues connect skeletal muscles and create a multidirectional framework, altered local forces from muscle contraction may affect the mechanics of distant or adjacent tissues forming functional units in series or in parallel.
SUMMARY OF THE FASCIAL SYSTEM RESPONSE TO ALTERED LOADING (EXERCISE), TO INJURY AND AGING
Both tissue repair from excessive fascial loading or trauma as well as overproduction of cytokines contribute to increased collagen in fascial tissues. Fibrosis around the tendon, nerve and myofascial tissues influences dynamic biomechanical properties secondary to tissue adherence and can tether structures to each other or induce chronic compression.
Muscle undergoes changes in response to injury not related to muscle. After an injury to an intervertebral disc, deep back muscles undergo atrophy, changes in composition, fibrosis and fatty infiltration due to increased cytokines. Fibrotic changes in the muscle have a substantial impact on tissue dynamics and force generation capacity.
Reduced inflammation can occur with:
- Anti-inflammatories which decrease collagen
- Stretching of fascial tissues and manual therapy to prevent overuse-induced fibrosis
- Resistance exercise to reverse fatty changes (and perhaps fibrosis) in chronic states
- Muscle activation to reverse early muscle atrophy
- Whole body exercise for back muscles that follow disc injuries
Tendons respond to chronic over and under loading by increasing and decreasing their stiffness respectively. It is unclear whether this is accomplished by altering tendon size or Young’s modulus.
HIGHLIGHTS OF THE CONTEMPORARY VIEW OF INTERVENTIONS TARGETING FASCIAL TISSUE IN SPORT AND EXERCISE MEDICINE
- Fascial tissue dysfunction is rarely treated surgically