title: A comparison of models of force production during stimulated isometric ankle dorsiflexion in humans.
abstract: In this paper, we compare seven models on their ability to fit isometric muscle force. We stimulated the ankle dorsiflexors of eight subjects at seven ankle angles (85 degrees-120 degrees). Three different stimulation patterns (twitch, triangular, and random) were applied at all ankle angles. Four additional patterns (doublets, steady rates, "catch property," and walking-like) were applied at 95 degrees. Parameter values were optimized for each model at each angle. Parameters for the general linear model were calculated using a novel least-squares algorithm. A linear, second-order critically damped model gave the poorest fits (average root mean square (rms) error: 15 N). The models of Ding et al. (2002) and Bobet and Stein (1998) gave the best fits (average rms errors: 9.2 and 9.4 N). The other models (general linear second-order model, Wiener model, Zhou et al. (1995) model, general linear model) gave intermediate results. Results were similar at all ankle angles. We conclude that the Ding and Bobet-Stein models are the best overall for isometric contractions, that no linear model of any kind will give an error less than 9% of maximum force, and that the models tested are consistent across lengths.
authors.affiliation: Centre for Neuroscience, University of Alberta, Edmonton, Canada.
authors.forename: Jacques
authors.initials: J
authors.lastname: Bobet
authors.forename: E Roderich
authors.initials: ER
authors.lastname: Gossen
authors.forename: Richard B
authors.initials: RB
authors.lastname: Stein
mesh_terms: D000843:Ankle Joint / Q000502:physiology*; D003198:Computer Simulation; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D016014:Linear Models; D008297:Male; D008954:Models, Biological; D018482:Muscle, Skeletal / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology; D013314:Stress, Mechanical