title: EMG-Driven Optimal Estimation of Subject-SPECIFIC Hill Model Muscle-Tendon Parameters of the Knee Joint Actuators.
abstract: the purpose of this paper is to propose an optimal control problem formulation to estimate subject-specific Hill model muscle-tendon (MT-) parameters of the knee joint actuators by optimizing the fit between experimental and model-based knee moments. Additionally, this paper aims at determining which sets of functional motions contain the necessary information to identify the MT-parameters.
  
  
  
  the optimal control and parameter estimation problem underlying the MT-parameter estimation is solved for subject-specific MT-parameters via direct collocation using an electromyography-driven musculoskeletal model. The sets of motions containing sufficient information to identify the MT-parameters are determined by evaluating knee moments simulated based on subject-specific MT-parameters against experimental moments.
  
  
  
  the MT-parameter estimation problem was solved in about 30 CPU minutes. MT-parameters could be identified from only seven of the 62 investigated sets of motions, underlining the importance of the experimental protocol. Using subject-specific MT-parameters instead of more common linearly scaled MT-parameters improved the fit between inverse dynamics moments and simulated moments by about 30% in terms of the coefficient of determination (from [Formula: see text] to [Formula: see text]) and by about 26% in terms of the root mean square error (from [Formula: see text] to [Formula: see text] ). In particular, subject-specific MT-parameters of the knee flexors were very different from linearly scaled MT-parameters.
  
  
  
  we introduced a computationally efficient optimal control problem formulation and provided guidelines for designing an experimental protocol to estimate subject-specific MT-parameters improving the accuracy of motion simulations.
  
  
  
  the proposed formulation opens new perspectives for subject-specific musculoskeletal modeling, which might be beneficial for simulating and understanding pathological motions.
authors.forename: Antoine
authors.initials: A
authors.lastname: Falisse
authors.forename: Sam
authors.initials: S
authors.lastname: Van Rossom
authors.forename: Ilse
authors.initials: I
authors.lastname: Jonkers
authors.forename: Friedl
authors.initials: F
authors.lastname: De Groote
mesh_terms: D000328:Adult; D003198:Computer Simulation; D055119:Elastic Modulus / Q000502:physiology; D004576:Electromyography / Q000379:methods*; D056966:Excitation Contraction Coupling / Q000502:physiology; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D008959:Models, Neurological; D009068:Movement / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology; D013710:Tendons / Q000502:physiology*; D013718:Tensile Strength / Q000502:physiology; D019415:Torque