Skeletal muscle has a complex hierarchical organization in which thousands of force-producing muscle fibers are arranged within a connective tissue network to work in concert and actuate movement. The properties of individual fibers have been studied in isolation over the last four decades. However, how the behaviors of muscle fibers may change once they are arranged within muscle is not well understood. Therefore, simplified one- or two-dimensional geometric models of muscle, which assume that all fibers act independently and shorten uniformly, are generally used to mathematically represent whole muscle.

In this presentation, I will describe a new framework for creating three-dimensional (3D) mechanics-based models of muscle from medical image data. These models can be used to explore how the arrangement of muscle fibers affects muscle function to a level of detail that has not been possible in the past. For example, we used the new formulation to understand how complex features of muscle architecture could cause nonuniform strains along muscle fascicles and to characterize how variations in moment arms of fibers within muscles affects muscle moment-generating capacity.

Insights gained from these models offer the potential to improve our ability to mathematically represent muscle behavior and enhance the accuracy of musculoskeletal models used for a wide variety of applications. More broadly, the modeling framework provides a new paradigm for exploring muscle structure-function relationships that will lead to new insights into the principles of skeletal muscle design.