Mechanobiological approach for skeletal muscle adaptation

Abstract

Skeletal muscle adaptation includes changes in shape and size, changes at the organelle function and distribution inside muscle cells, and changes at the molecular scale. Prolonged repetition of loading conditions (physical activity and exercise) promote the activation or inhibition of certain biochemical species related to protein content (muscle fiber size) and protein isoform differentiation (muscle fiber type). Current muscle-function models are not suitable to describe muscle adaptation for three main reasons: first, current models typically focus on muscle contraction, which occurs in the time scale of seconds; second, the mechanical description uses fixed parameters or parameters that are not controlled by biological aspects; and third, the mechanics of growth considers only sustained boundary conditions and overlooks biological aspects. The aim of this research is to mathematically model muscle adaptation by considering two biological aspects of the adaptation process (protein synthesis and gene-program switch), and a continuum mechanical model whose parameters evolve according to the biological part of the model. This thesis presents new models for the adaptation of skeletal muscle protein content, cross sectional area (CSA), maximum voluntary contraction (MVC) and fiber distribution.