Biochemical and Structural Basis of the Passive Mechanical Properties of Whole Skeletal Muscle

This review discusses how passive properties of skeletal muscle, which are present even when the muscle is not actively contracting, scale from the microscopic level of single muscle cells to the macroscopic level of whole muscles. The authors highlight that the 'feel' of the muscle, which relates to passive mechanical properties, is often used in surgical settings, but these properties are not uniform across muscles. The review emphasizes that the extracellular matrix (ECM), the connective tissue surrounding muscle fibers, plays a crucial role in bearing passive loads, especially at larger scales. Alterations in ECM composition and structure can significantly impact muscle stiffness and function, particularly in conditions like muscular dystrophy and cerebral palsy.

• 1
  Titin bears the majority of passive load within the single muscle cell.
• 2
  At larger scales, such as fascicles and muscles, there is emerging evidence that the extracellular matrix (ECM) bears the majority of the load.
• 3
  Passive mechanics are not uniquely related to sarcomere length but are more likely related to their operational range or functional use.