Abstract: The need to model muscles means different things to artistic and technical practitioners. Three different muscle representations are presented and the motivations behind their design are discussed. Each representation allows unique capabilities and operations to be performed on the model, yet the underlying mathematical foundation is the same for all. This is achieved by developing a data-fitting pipeline that allows samples that are generated from different data sources to be used in the guided construction of a B-spline solid. We show how B-spline solids can be used to create muscles from contour curves extracted out of medical images, digitized fibre sets from dissections of muscle specimens, and profile curves that can be interactively sketched and manipulated by an anatomical modeller.