Are the maximum shortening velocity and the shape parameter in a Hill-type model of whole muscle related to activation?

• Published in: Journal of biomechanics 2005-11, Vol.38 (11), p.2172-2180
• Main Authors: Camilleri, M.J., Hull, M.L.
• Format: Article
• Language: English
• Subjects: Accuracy; Activation; Adult; Biomechanical Phenomena; Concentric; Contraction; Elbow Joint - physiology; Electromyography; Ergometry; Female; Hill parameter; Humans; Kinetics; Male; Models, Biological; Movement - physiology; Muscle; Muscle Contraction - physiology; Muscle, Skeletal - physiology; Muscular system; Recruitment; Scaling; Simulation; Studies; Triceps brachii; Velocity
• ISSN: 0021-9290; 1873-2380
• DOI: 10.1016/j.jbiomech.2004.09.037

Mathematical models of the inter-relationship of muscle force, velocity, and activation are useful in forward dynamic simulations of human movement tasks. The objective of this work was to determine whether the parameters (maximum shortening velocity V max and shape parameter k) of a Hill-type muscle model, interrelating muscle force, velocity, and activation, are themselves dependent on the activation. To fulfill this objective, surface EMG signals from four muscles, as well as the kinematics and kinetics of the arm, were recorded from 14 subjects who performed rapid-release elbow extension tasks at 25%, 50%, 75%, and 100% activation (MVC). The experimental elbow flexion angle was tracked by a forward dynamic simulation of the task in which V max and k of the triceps brachii were varied at each activation level to minimize the difference between the simulated and experimental elbow flexion angle. Because a preliminary analysis demonstrated no dependency of k on activation, additional simulations were performed with constant k values of 0.15, 0.20, and 0.25. The optimized values of V max normalized to the average value within a subject were then regressed onto the activation. Normalized V max depended significantly on the activation ( p