Contribution of elastic tissues to the mechanics and energetics of muscle function during movement

Abstract

Muscle force production occurs within an environment of tissues that exhibit spring-like behavior, and this elasticity is a critical determinant of muscle performance during locomotion. Muscle force and power output both depend on the speed of contraction, as described by the isotonic force-velocity curve. By influencing the speed of contractile elements, elastic structures can have a profound effect on muscle force, power and work. In very rapid movements, elastic mechanisms can amplify muscle power by storing the work of muscle contraction slowly and releasing it rapidly. When energy must be dissipated rapidly, such as in landing from a jump, energy stored rapidly in elastic elements can be released more slowly to stretch muscle contractile elements, reducing the power input to muscle and possibly protecting it from damage. Elastic mechanisms identified so far rely primarily on in-series tendons, but many structures within muscles exhibit springlike properties. Actomyosin cross-bridges, actin and myosin filaments, titin, and the connective tissue scaffolding of the extracellular matrix all have the potential to store and recover elastic energy during muscle contraction. The potential contribution of these elements can be assessed from their stiffness and estimates of the strain they undergo during muscle function. Such calculations provide boundaries for the possible roles these springs might play in locomotion, and may help to direct future studies of the uses of elastic elements in muscle.

Magnetic resonance elastography of the lumbar back muscles: A preliminary study

“…LPM stiffness increased significantly during stretching and contraction, and this must be related to underlying biological events such as the elastic properties of actomyosin cross‐bridges, hyperemia and edema, and changes in the scaffold of the extracellular matrix (Sarelius et al, ; Roberts, ). Previous studies using SWE and MRE reported positive linear relationships between muscle stiffness and both active and passive muscle forces (Nordez and Hug, ; Hug et al, ).…”

Altered Protein Composition and Gene Expression in Strabismic Human Extraocular Muscles and Tendons

“…36,37 We found that myosin isoforms 2, 7, and 13 were reduced at either the protein or gene expression level in strabismic muscles, along with several filament- and contraction-related proteins that included troponins, tropomyosins, and titin (Table 1). Titin confers passive elasticity to muscles 40–43 ; accordingly, its downregulation may impact and compromise EOM stiffness. Analysis of mutant tropomyosins (causing nemaline myopathy) revealed reduced isometric force when measured in muscles of less than optimal length.…”

An investigation into the variability between different shear wave elastography systems in muscle

“…Muscle stretch and contraction elastic elements are major determinants of muscle function and efficient locomotion [4,5]. The measurement of these parameters has largely been explored using myotonometry but this has not been shown to have acceptable accuracy and is limited to superficial muscles only [6,7].…”