There is no slowing of motility speed with increased body size in rat, human, horse and rhinoceros independent on temperature and skeletal muscle myosin isoform

Abstract

The scaling effect of body size and limb length on shortening velocity at the muscle fibre level, i.e. the decreasing shortening velocity associated with increasing body weight and limb length, was not confirmed at the motor protein level when including mammals of very large size. Thus, other factors than myosin structure and function appear to cause this scaling effect and thin filament isoform expression or myofilament lattice spacing are forwarded as alternative underlying factors.

Sarcopenia: Aging-Related Loss of Muscle Mass and Function

“…In the study of aging-related changes in myosin function, the single muscle fiber in vitro motility assay offers the opportunity to conduct detailed studies of the catalytic properties (motility speed) and force generation capacity of specific myosin isoforms or combinations of isoforms extracted from a single muscle fiber segment with a known myosin isoform expression (403, 404, 406, 558 -561, 740, 741). In addition, myosin function can be investigated in detail in any mammalian species, including humans (559). The single fiber in vitro motility assay has become a critical method for the study of myosin function [i.e., catalytic properties (motility speed) and force generation capacity during aging and the viscous drag produced by the solution in the experimental chamber when fluorescent-labeled actin filaments are driven by myosin is negligible compared with the force produced by the motor protein].…”