Fascia is a fibrous network of connective tissue in the body that surrounds all structures. Fascia holds parts in place, suspends organs, nerves and blood vessels, transfers the pull of the muscles and allows different parts of the body to move freely by forming distinct layers of tissue that can slide smoothly across each other.
Fascia is made of three major components; fibers, extracellular matrix (ECM) and cells. Fibers contribute to the mechanical properties, ECM enables malleability and cells provide metabolic properties. The most common type of cell in fascia is the fibroblast. Fibroblasts produce the ECM’s structural and adhesive proteins and ground substance and form a mesh-like structure with contractile fibers. The flexibility of these fibers allows the fascia to adjust tension levels rapidly, providing swift support during times of stress.
Fibroblasts play a crucial role healing wounds. They respond by proliferating and moving to the injury site to rebuild the ECM as a scaffold for regeneration. Under mechanical stress, certain fibroblasts can differentiate into proto-myofibroblasts, which build more actin fibers (thin filaments that are part of the contractile apparatus in muscle and nonmuscle cells) and connect them to adhesion sites. Further mechanical and chemical stimulation can result in fully differentiated myofibroblasts.
Myofibroblasts, with an elevated production rate of extracellular matrix (ECM), express an actin–myosin complex akin to smooth muscle, embodying a blend of fibroblast and smooth muscle cell traits. This accelerates wound closure by contracting and bringing the wound edges together.
Various factors, such as mechanical tension and pharmacological alterations in the tissue, can prompt this transformation. Typically present in wounds, myofibroblasts play a crucial role in contracting wound edges, facilitating efficient closure and speedy repair.
Myofibroblasts are found in higher concentrations in damaged fascia that’s healing and in high stress areas. Fascia responds to stressful tensile forces by developing more myofibroblasts. For this reason, myofibroblasts are also known as “stress fibers”. High concentrations of myofibroblasts can create an active pulling force in fascia and have been found to have enough force to impact musculoskeletal mechanics and affect movement.
The contraction of muscle tissue is governed by the nervous system, through reflexes or conscious thought. It can respond almost instantaneously to triggers. The contraction of myofibroblasts in fascia is different, more like smooth muscle. The contraction of fascia is not directly influenced by mental intention but by physical stress. It builds up in 90 second cycles, accumulating over a period of minutes to hours, in slow and steady contractions, with no relaxation and no neural input.
Since contraction forces may be strong enough to influence musculoskeletal dynamics, imbalance of this regulatory mechanism can result in altered myofascial tonus or interfere with neuromuscular coordination, 2 key contributors to musculoskeletal dysfunction and pain.
Healthy fascial fibers, bundles and layers align neatly to support, slide and transfer force. Through exercise, trauma, inactivity and age these fibers can become shorter, frayed, stiff and stuck together. What used to aid and support movement can now create limitations. Massage with myofascial work followed by constructive exercise can help your horse regain movement and balance.
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