title: An action potential-driven model of soleus muscle activation dynamics for locomotor-like movements.
abstract: OBJECTIVE
  The goal of this study was to develop a physiologically plausible, computationally robust model for muscle activation dynamics (A(t)) under physiologically relevant excitation and movement.
  
  
  METHODS
  The interaction of excitation and movement on A(t) was investigated comparing the force production between a cat soleus muscle and its Hill-type model. For capturing A(t) under excitation and movement variation, a modular modeling framework was proposed comprising of three compartments: (1) spikes-to-[Ca(2+)]; (2) [Ca(2+)]-to-A; and (3) A-to-force transformation. The individual signal transformations were modeled based on physiological factors so that the parameter values could be separately determined for individual modules directly based on experimental data.
  
  
  RESULTS
  The strong dependency of A(t) on excitation frequency and muscle length was found during both isometric and dynamically-moving contractions. The identified dependencies of A(t) under the static and dynamic conditions could be incorporated in the modular modeling framework by modulating the model parameters as a function of movement input. The new modeling approach was also applicable to cat soleus muscles producing waveforms independent of those used to set the model parameters.
  
  
  CONCLUSIONS
  This study provides a modeling framework for spike-driven muscle responses during movement, that is suitable not only for insights into molecular mechanisms underlying muscle behaviors but also for large scale simulations.
authors.affiliation: Division of Robotics Research, Daegu Gyeongbuk Institute of Science and Technology, Daegu 711-873, Korea. Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago 60611, USA.
authors.forename: Hojeong
authors.initials: H
authors.lastname: Kim
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Sandercock
authors.forename: C J
authors.initials: CJ
authors.lastname: Heckman
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D020013:Calcium Signaling / Q000502:physiology; D002415:Cats; D003198:Computer Simulation; D005684:Gait / Q000502:physiology; D006801:Humans; D008124:Locomotion / Q000502:physiology*; D008959:Models, Neurological; D009046:Motor Neurons / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*