Functional bases of fiber length and angulation in muscle

Abstract

The differences in angulation and length observed for the fibers of anatomical muscles may reflect two distinct mechanical requirements: arrangement for pinnation, reflecting an increase in physiological cross-section and arrangement for equivalent placement of sarcomeres, possibly associated with coordination. The observed differences in fiber angulation and length have different effects upon the responses of sarcomeres, specifically on their extent and rate of shortening and on the force they may generate. The basic mechanisms governing these effects and the various arrangements of muscles are reviewed. Fiber length and angulation in the complex M. adductor mandibulae externus 2 of a lizard were measured stereotactically; these values correlate well with the hypothesis that the muscle shows equivalence and demonstrate that angulation for pinnation is less constant. An outline for the study of muscle architecture and function, detailing the kinds of information require to estimate forces and evaluate muscle and fiber placements, is presented.

Changes in pennate muscle architecture after gradual tibial lengthening in goats

“…Numerous studies have examined how the PA affects normal muscle anatomy, architecture, and physiological function (Muhl, 1982;Gans and de Vree, 1987;Lieber and Blevins, 1989;Gans and Gaunt, 1992;Scott et al, 1993;Van Eijden et al, 1997;Ledoux et al, 2001;Maganaris et al, 2001). Previous PA studies have focused only on the PA of the muscle fibers located at the muscle belly surface (Muhl, 1982;Sacks and Roy, 1982;Lieber and Blevins, 1989;Scott et al, 1993;Van Eijden et al, 1997;Ledoux et al, 2001;Maganaris et al, 2001).…”

“…It has also been reported that PA may vary within the same normal muscle (Gans and de Vree, 1987). In this study, PA measurement was limited to the middle portion of the muscle in order to eliminate the variability at the proximal and distal ends of the muscle belly.…”

“…Changes in other parameters, such as the muscle fiber pennation angle and muscle aponeurosis length, should also be considered during limb lengthening. Pennation angle (PA) is the angle between muscle fibers and the long axis of muscle movement (Gans and de Vree, 1987;Gans and Gaunt, 1992).…”

“…It is an important architectural parameter that allows different arrangements of muscle fibers and therefore affects skeletal muscle function (Muhl, 1982;Gans and de Vree, 1987;Gans and Gaunt, 1992). Both FL and the cosine of PA are components of the standard formula used to calculate the muscle physiological cross-sectional area (PCSA) (Sacks and Roy, 1982;Lieber, 2002), which is the only muscle architectural parameter that is directly proportional to the maximum tetanic tension of the muscle, hence to its ability of force production (Lieber, 2002).…”

“…Both FL and the cosine of PA are components of the standard formula used to calculate the muscle physiological cross-sectional area (PCSA) (Sacks and Roy, 1982;Lieber, 2002), which is the only muscle architectural parameter that is directly proportional to the maximum tetanic tension of the muscle, hence to its ability of force production (Lieber, 2002). Although numerous studies evaluated how the PA affects normal muscle anatomy and physiological function (Muhl, 1982;Gans and de Vree, 1987;Lieber and Blevins, 1989;Gans and Gaunt, 1992;Scott et al, 1993;Van Eijden et al, 1997;Ledoux et al, 2001;Maganaris et al, 2001), little is known about the effect of gradual distraction on muscle fiber PA and PCSA.…”