Passive changes in muscle length

Abstract

This review, the first in a series of minireviews on the passive mechanical properties of skeletal muscles, seeks to summarize what is known about the muscle deformations that allow relaxed muscles to lengthen and shorten. Most obviously, when a muscle lengthens, muscle fascicles elongate, but this is not the only mechanism by which muscles change their length. In pennate muscles, elongation of muscle fascicles is accompanied by changes in pennation and changes in fascicle curvature, both of which may contribute to changes in muscle length. The contributions of these mechanisms to change in muscle length are usually small under passive conditions. In very pennate muscles with long aponeuroses, fascicle shear could contribute substantially to changes in muscle length. Tendons experience moderate axial strains even under passive loads, and, because tendons are often much longer than muscle fibers, even moderate tendon strains may contribute substantially to changes in muscle length. Data obtained with new imaging techniques suggest that muscle fascicle and aponeurosis strains are highly nonuniform, but this is yet to be confirmed. The development, validation, and interpretation of continuum muscle models informed by rigorous measurements of muscle architecture and material properties should provide further insights into the mechanisms that allow relaxed muscles to lengthen and shorten.

The passive mechanical properties of muscle

“…Each minireview addresses an aspect of the passive mechanical properties of skeletal muscles. Topics include passive changes in muscle length (8), contemporary imagebased methods for measuring passive mechanical properties of skeletal muscles in vivo (1), epimuscular force transmission under passive conditions (15), passive force enhancement (9), properties of titin (6), muscle thixotropy (13), mechanical properties and physiological behavior of tendon (4), adaptations of the passive properties of skeletal muscle to altered patterns of use (2), and muscle contracture in cerebral palsy (14).…”

Muscle Length of the Hamstrings Using Ultrasonography Versus Musculoskeletal Modelling

“…There are various factors that could have contributed to the greater change in LMTU by SM than the remainder hamstrings. Since SM and BFlh are pennated muscles, they may experience greater change in length during passive motion than the fusiform ST [27]. Differences in tendon properties and moment-arms may also influence length changes, but the exact contribution is still unclear [5].…”

Changes in neural drive to calf muscles during steady submaximal contractions after repeated static stretches

“…2019), and the stretch‐induced changes in muscle, tendon and connective tissue properties likely differ when measured passively versus over a range of different forces (Herbert et al . 2019; Muramatsu et al . 2001), as well as when quantified as separate components (Zhou et al .…”

“…Moreover, the influence of myofascial and epimuscular force transmission on triceps surae function is not trivial (Maas and Sandercock, 2010;Finni et al 2017;Crouzier et al 2018;Ruttiman et al 2019), and the stretch-induced changes in muscle, tendon and connective tissue properties likely differ when measured passively versus over a range of different forces (Herbert et al 2019;Muramatsu et al 2001), as well as when quantified as separate components (Zhou et al 2019;Chino and Takahashi, 2020). For example, force generation and transmission during various contraction intensities and muscle lengths may be influenced by changes in aponeurosis morphology (Muramatsu et al 2001;Raiteri et al 2018) or via connective tissues between synergists independent of changes in fascicle length (Tijs et al 2018).…”