Editorial: Muscle Mechanics, Extracellular Matrix, Afferentation, Structural, and Neurological Coupling and Coordination in Health and Disease.

Due to a highly variable distribution of intramuscular collagen content within muscle, the amount collagen content itself does not relate to the actual passive muscle properties during mechanical testing as was shown in mouse hind limb muscles (Binder-Markey et al.). Keywords: muscle mechanics; extracellular matrix; connective tissue; neuromusculoskeletal interaction; adaptation; pathology; force production - transmission phenomena EN muscle mechanics extracellular matrix connective tissue neuromusculoskeletal interaction adaptation pathology force production - transmission phenomena 1 6 6 12/08/21 20211206 NES 211206 There is a growing emphasis on the importance of muscle extracellular matrix on muscular mechanics and specifically on the effects of the interaction of the extracellular matrix (ECM) and the contractile apparatus. An experimental assessment using multi-photon excitation microscopy in mouse tibialis anterior muscle surgically dissected from the tibia and surrounding muscles showed that in isometrically activated muscle the sarcomeres re-organize their lengths into a more uniform pattern over time, whereas in the passive state their length non-uniformity remained the same (Moo and Herzog). They demonstrate how a passively lengthened muscle can also have shortened parts and how an isometric contracting muscle can also have lengthened parts along the muscle fascicles. [Extracted from the article]