Sarcomeres can undergo spontaneous oscillatory contraction (SPOC)—cyclic length changes observable in a single myofibril. In native muscle, however, many myofibrils are laterally linked, allowing oscillations to propagate as surface or volumetric waves. This paper extends the traditional “one‑row model” by adding lateral springs that bridge Z‑lines and M‑lines and by incorporating end‑compliance, thereby constructing two‑ and three‑dimensional models that reproduce the rich SPOC waveforms seen in bundled myofibrils.
Simulation insights
Weak lateral stiffness → each filament row vibrates independently and incoherently.
Intermediate stiffness → waves align to form a phase‑locked traveling wave.
Strong stiffness → all sarcomeres beat in phase across the bundle.
Heterogeneous coupling produces phase‑decoupling waves whose propagation speed changes over time, matching complex patterns reported experimentally.
These results suggest that the ordered‑to‑disordered transitions of beating observed inside muscle fibers are highly sensitive to the mechanical properties of lateral cross‑linkers and external load. The study thus offers a theoretical framework in which tissue stiffening or cross‑link protein defects can lead to rhythm disorders via mechanical phase transitions in the myofibril network.
Article information & citation
Koutaro Nakagome, Katsuhiko Sato, Seine A Shintani, Shin’ichi Ishiwata. Model simulation of the SPOC wave in a bundle of striated myofibrils. Biophysics and Physicobiology 13, 217‑226 (2016).