Muscle fiber types expressing different myosin heavy chain isoforms. Their functional properties and adaptive capacity

In this review we present recent results of a collaborative study aimed at: 1) identifying the myosin heavy chain (MHC) isoforms expressed by various fiber types in rat and mouse skeletal muscle, 2) correlating the MHC profile with functional properties, 3) identifying factors responsible for modulating the fiber type phenotype and 4) defining the adaptive capacity of different fiber types with respect to MHC isoform expression. This report is mainly focused on a new major subset of type 2 muscle fibers defined by the presence of a distinct MHC isoform, that we have recently identified in rat and mouse skeletal muscle.