Poster Presentation 2014 International Biophysics Congress

A systematic muscle model simulating the fast ramp stretches in the muscle fibres (#387)

Youjiro Tamura 1 , Akira Ito 1 , Andrew G. Cresswell 2 , Masami Saito 3
  1. Suzuka National College of Technology, Suzuka, Japan
  2. School of Human Movement Studies, The University of Queensland, Brisbane, QLD, Australia
  3. Yonago National College of Technology, Yonago, Japan

We have proposed a muscle model which consists of two Maxwell elements and a Voigt element in parallel. The muscle model is essentially different from Hill-type models, because the Hill-type models are series array of a spring and a contractile component. We have applied the muscle model to the force changes due to quick and slow length changes in the muscle and succeeded to simulate various kinds of the force changes (Tamura et al., 2005, 2014). Bagni et al. (1998) measured the force responses to fast ramp stretches in frog skeletal muscle fibres. In their experiments, they recorded the velocity changes during the fast ramp stretches. The force response is composed of an initial fast phase followed by a slower one during the fast ramp stretches. The initial fast phase lasts for the acceleration period during which the stretching velocity rises up to steady state. The second slower phase lasts for the remainder of the stretch, showing the property of the well-known series elastic component of the fibres. In this study, we used the muscle model to understand the experimental results, considering that the initial fast phase comes from properties of a viscous element in parallel. The simulation results confirm the idea, showing that the model is applicable well. Since the viscosity of the Voigt element is centesimal of that of the Maxwell element, we think that the viscosity originates not in the cross-bridges but in the parallel components like titin and/or collagen.

  1. Y.Tamura, M.Saito & R.Nagato, 2005 A new motor model representing the stretch-induced force enhancement and shortening-induced force depression in skeletal muscle. J. Biomechanics, 38: 877-884.
  2. Y.Tamura, A.Ito & A.G.Cresswell, 2013: A systematic muscle model covering regions from the fast ramp stretches in the muscle fibres to the relatively slow stretches in the human triceps surae. Computer Methods in Biomechanics and Biomedical Engineering. Epub DOI:10.1080/10255842.2013.790016
  3. M.A.Bagni, G.Cecchi, E.Cecchini, B.Colombini & F.Colomo, 1998 Force responses to fast ramp stretches in stimulated frog skeletal muscle fibres. J.Muscle Research and Cell Motility 19: 33-42.