Surface-based modeling of muscles: Functional simulation of the shoulder.

•We propose to use surface geometries for modeling muscles, simulated as membrane within a finite element simulation.•Surface-based models are a stable and computationally efficient compromise between line-segment and volumetric models.•Our proposed models allow for subject-specific customization, fast simulations, and anatomically consistent wrapping and moment arms.•We present methods for building a comprehensive model of the upper limb, where muscle activations are obtained via inverse dynamics.•Our functional simulation is shown to successfully replicate tracked shoulder motion during activities of daily living, also exemplifying a pathological case.