Sliding filament models of muscle contraction interconnect the actomyosin ATPase cycle, thin filament regulation, and the structural arrangement of myosin and actin filaments into the sarcomere lattice. These models of various levels of complexity predict the dynamic response of muscle to Ca²⁺ activation and external boundary loads. (A) The simulations of classical muscle experiments follow the experimental protocols, including Ca²⁺ activation and force or length as inputs, and predict length or force along with muscle stiffness and ATPase. These models are typically designed to address a specific scientific problem. (B) The modular structure of the MUSICO platform is designed to address many different scientific problems by adding new modules or adapting existing modules for the specifics for each problem. The flexible structure of the platform permits the use of various combinations of actomyosin cycles, thin filament regulatory models, sarcomere structures, and protocols of biochemical and mechanical loading. The relevant parts of the model reported here are shown in black, whereas the parts reported elsewhere or planned for future studies are shown in gray.