The striated muscle has multiple hierarchical structures, the organ that contracts in it is called myofibril, and the series of units that make up it is called sarcomere (myomere).Sarcomere is a stack of proteins (actin and myosin) that expands and contracts individually.Myosin swings and contracts sarcomere by using the hydrolysis energy of adenosine triphosphate (ATP) from the stretched state where the muscle is weak.Sarcomere has the property of "self-excited vibration contraction" that repeats contraction and expansion (relaxation).

　The research team has conducted research to mathematically analyze the mechanism of the contraction rhythm of self-excited vibration contraction by myosin.In 2017, we succeeded in explaining the self-excited vibration contraction phenomenon using a mathematical model, assuming that myosin draws reverse power when it receives a mechanical load.

　Now, the force that tries to align the lattice spacing between adjacent sarcomere and the force that tries to maintain the inverse relationship between the longitudinal and longitudinal strains of the sarcomere increases the mechanical load on myosin in the contracting sarcomere. The mathematical model was corrected in consideration of the effect.As a result, the waves propagating when Sarcomere aligns the vibration timing could be faithfully reproduced.In addition, the same mathematical model could explain the self-excited vibration contraction of the human myocardium and the flying muscle of the beetle (about 5 times faster than the human myocardium).

　This achievement is expected to contribute to the improvement of medical technology such as advance prediction of heart failure.

Paper information:[Scientific Reports] Effect of myofibril passive elastic properties on the mechanical communication between motor proteins on adjacent sarcomeres