Neuromuscular Dynamics in the Context of Motor Redundancy

xvi Chapter 1: Introduction, Background and Prior Work 1 1.1 Motor Redundancy . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Muscle Fatigue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.3 Experimental Evidence: Leveraging Muscle Redundancy for Fatigue Mitigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 1.4 Modeling and Simulation: Muscle Redundancy and Muscle Fatigue . . 10 Chapter 2: Fatigue Dynamics Have Profound Consequences for Muscle Coordination and Theories of Motor Control 14 2.1 Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.3 Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2.3.1 Modeling a redundant neuromuscular system . . . . . . . . . . 19 2.3.2 Mathematical modeling of fatigue . . . . . . . . . . . . . . . . 25 2.3.3 Simulating muscle activation dynamics in isometric knee extension subject to optimization . . . . . . . . . . . . . . . . . . . 27 2.3.4 Parameter search . . . . . . . . . . . . . . . . . . . . . . . . . 29 2.4 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 2.4.1 Eureqa-extracted dynamics of muscle fatigue and recovery . . . 30 2.4.2 Running the nominal model subject to optimized activation . . . 32 2.4.3 Parameter search results . . . . . . . . . . . . . . . . . . . . . 34 2.5 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39