The fascia: Continuum linking bone and myofascial bag for global and local body movement control on Earth and in Space. A scoping review

Purpose: The fascia receives more and more attention as functional component of the body in fundamental and applied human life sciences on Earth. As shaping element of the human body movement apparatus the fascia comprises a multicellular three dimensional layer of connective tissue components (collagens, fibrocytes/-blasts, extracellular matrix), more specialized fibroblast-derived cells (fascia-, telocytes), contracting myofibroblasts, mechano- and propriosensors, and nociceptors. Fascia is a multicellular/multicomponent biological material for human body structural and functional integration as well as serving as a sensation organ in terms of movement and performance adjustment, body awareness and control. Methods: The present scoping review elaborates on structure, function and biomechanical properties (tone, stiffness, viscoelasticity) of fascia mainly selected from recent literature data in order to highlight the role of the loading-sensitive i.e. structural and biomechanical support mechanisms of this ensheathment structure that can influence shape, body motions and performance on Earth. Results: Superficial and deep fascia of skeletal musculature is a continuum structure thus linking muscle, tendon and bone to provide a unique tensional support system that stores about 20 percent of total muscle force production. First own studies on the normal healthy human body showed that equally to muscle and tendon fascia is susceptible to disuse conditions on Earth. Like muscle, fascia can be re-enforced by high-load physical exercise as countermeasure in laboratory set-ups (i.e. bed rest) on the ground. If and to what magnitude fascia structure and property are affected in microgravity is an open issue that warrants further investigations on fascial adaptation in real spaceflight. Conclusion: Elucidation of the fascia conundrum in human performance requires improved assessment tool development for interdisciplinary investigations under normal conditions, in clinical rehabilitation on Earth, and following de-/reconditioning of astronaut́s performance in environmental and space medicine.