Dynamics of biomechanisms: musculotendon mass, constraints, and architecture

We examine some basic assumptions underlying current musculoskeletal simulators and suggest alternative solutions. First, we discuss the role of muscle mass and show that current simulators may miss a fundamental feature of musculoskeletal dynamics. Second, we discuss the importance of efficient and versatile constraint handling. Even though the complexity of joint constraints is well recognized, soft tissue constraints due to tendon networks, connective tissue sheaths, and contact between muscles play an important role, and can not be easily represented in current simulators. We also describe simulators recently developed in our laboratory to address these issues and efficient and robust algorithms for simulating realistically large biomechanical systems.