title: ISOFIT: a model-based method to measure muscle-tendon properties simultaneously.
abstract: Estimation of muscle parameters specifying force-length and force-velocity behavior requires in general a large number of sophisticated experiments often including a combination of isometric, isokinetic, isotonic, and quick-release experiments. This study validates a simpler method (ISOFIT) to determine muscle properties by fitting a Hill-type muscle model to a set of isovelocity data. Muscle properties resulting from the ISOFIT method agreed well with muscle properties determined separately in in vitro measurements using frog semitendinosus muscles. The force-length curve was described well by the results of the model. The force-velocity curve resulting from the model coincided with the experimentally determined curve above approximately 20% of maximum isometric force (correlation coefficient R>0.99). At lower forces and thus higher velocities the predicted curve underestimated velocity. The stiffness of the series elastic component determined with direct experiments was approximately 10% lower than that determined by the ISOFIT method. Use of the ISOFIT method can decrease experimental time up to 80% and reduce potential changes in muscle parameters due to fatigue.
authors.affiliation: Department Science of Motion, Friedrich-Schiller-University Jena, 07749 Jena, Germany. heiko.wagner@uni-jena.de
authors.forename: H
authors.initials: H
authors.lastname: Wagner
authors.forename: T
authors.initials: T
authors.lastname: Siebert
authors.forename: D J
authors.initials: DJ
authors.lastname: Ellerby
authors.forename: R L
authors.initials: RL
authors.lastname: Marsh
authors.forename: R
authors.initials: R
authors.lastname: Blickhan
mesh_terms: D000465:Algorithms; D000818:Animals; D003198:Computer Simulation; D003936:Diagnosis, Computer-Assisted / Q000379:methods; D004548:Elasticity; D008954:Models, Biological; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D011894:Rana pipiens; D051381:Rats; D013314:Stress, Mechanical; D013710:Tendons / Q000502:physiology*