Towards Multi-Scale Modeling of Muscle Fibers with Sarcomere Non-Uniformities

The muscle is a hierarchical structure with structural components that span over several scales. The basic contractile unit of the muscle is the half-sarcomere that has a length of one micron.
Myofibrils, typically several millimeters long, are composed of thousands of sarcomeres connected in series. In turn, the muscle fiber contains a large number of aligned myofibrils.
There is a wide evidence for the existence of sarcomere non-uniformities in skeletal muscles. However, the importance of sarcomere non-uniformities to muscle function is still under debate. There is some indirect evidence that these non-uniformities play a significant role in muscle function and in phenomena such as creep, sensitivity of muscle tension to fiber length, and damage due to eccentric contraction. Importantly, these intriguing behaviors cannot be explained by classical cross-bridge theories (e.g.[4]). The main goal of this work is to develop a theoretical framework that enables a systematic and quantitative analysis of the role of non-uniformities in muscle function.