Kinematic linkage models of muscle contraction: A mechanical engineering perspective

This paper proposes a new kinematic linkage model for the actin-myosin contraction mechanism. For studying the mechanical movements, the structures of myosin and actin are first modeled using rigid links and kinematic pairs. A kinematic mechanism has been proposed taking into consideration the experimentally observed changes in the angles of the links. The model has been validated with the experimentally available stroke length of the actin during the power-stroke. The present work also revisits the classical swinging lever arm model (SLAM) and for the first time, proposes kinematic linkage model for SLAM. The prominent contribution of the paper is the development of a planar kinematic linkage model based on Nath's Rotation-Twist-Tilt (RTT)/Rotation-Uncoiling-Tilt (RUT) model. The value of torsional spring stiffness of 534 pN-nm/rad has been estimated based on the RTT/RUT model for the first time. It is shown that the proposed kinematic model validates the experimentally measured, 5.3 nm stroke length of the actin filament, reported in literature.