Muscle fibers are arranged in a complex hierarchical architecture that has 5 different structural scales.
Quantitative muscle biophysics has been dominated since the 1950's by reductionist theories that try to explain the mechanical properties of an entire muscle fiber as the scaled behavior of a single myosin head. Current modeling projects in the Campbell lab focus on the idea that muscle fibers also exhibit emergent properties, that is, mechanical effects that reflect interactions between different stuctures in the muscle fiber and are not properties of a single isolated structure.
Our first publication in this area showed that tension overshoots (the temporary increase in force above the steady-state level produced by some muscle fibers when they develop tension) may reflect "compliant realignment" of myosin heads and actin binding sites. In other words, the overshoot can be modeled as an emergent property of linear arrays of actin and myosin molecules.
Our second publication dealing with emergent properties considered higher level structures. We modeled what happens when half-sarcomeres are linked together to form parallel chains of myofibrils. Our results showed that the mechanical properties of this 'fiber' are not the same as the properties of the mean half-sarcomere.
We are now working on a multiscaled model that combines both of these effects: spatially-explicit half-sarcomeres linked together in series and in parallel.