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Published February 2009 | public
Journal Article

A coarse-grained model of the myofibril: Overall dynamics and the evolution of sarcomere non-uniformities


A theoretical framework for predicting the macroscopic behavior of a muscle myofibril based on the collective behavior of sarcomeres is presented. The analysis is accomplished by rigorously transforming the nonlinear dynamics of an assemblage of sarcomeres into a partial differential equation for the probability distribution function of sarcomere lengths in the presence of stochastic temporal fluctuations and biological variability. This enables the study of biologically relevant specimens with reasonable computational effort. The model is validated by a comparison to quantitative experimental results. Further, it reproduces experimental observations that cannot be explained by standard single sarcomere models, and provides new insights into muscle function and muscle damage during cyclic loading. We show that the accumulation of overstretched sarcomeres, which is related to muscle damage, depends on a delicate interplay between the dynamics of a large number of sarcomeres and the load characteristics, such as its magnitude and frequency. Further, we show that biological variability rather than stochastic fluctuations are the main source for sarcomere non-uniformities.

Additional Information

© 2008 Elsevier Ltd. Received 14 April 2008. Received in revised form 26 October 2008. Accepted 28 October 2008. This work was carried out when Sefi Givli held a position at the California Institute of Technology. We thank a reviewer for the insightful comment on the typical relaxation time according to Model F. We are grateful to the National Science Foundation (Grant DMS-060667), the Powell Foundation and the Lester Deutch Foundation (Post-doctoral fellowship) for their financial support.

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