Muscle machine: How water controls the speed of muscle contraction

Date:

July 11, 2024

Source:

University of Michigan

Summary:

The flow of water within a muscle fiber may dictate how quickly muscle can contract, according to a new study.

A study from the University of Michigan suggests that the movement of water within muscle fibers may determine how quickly muscles can contract. Led by physicist Suraj Shankar and Harvard's L. Mahadevan, the research explores a theoretical model where fluid dynamics within muscle fibers affect contraction speed.

They discovered that muscles exhibit a unique elasticity known as "odd elasticity," enabling them to generate power through three-dimensional deformations. This includes observations where muscle fibers not only contract lengthwise but also expand perpendicularly.

Their findings, published in Nature Physics, propose that understanding water's role in muscle contraction could influence the design of soft actuators, artificial muscles, and shape-morphing materials. These technologies currently have slow contraction speeds due to external triggers.

The study challenges traditional views that focused solely on molecular mechanisms, emphasizing instead the holistic view of muscle as a complex, water-rich material. This perspective suggests that muscle performance, including the speed and power generation capabilities, is influenced by its fluid dynamics and hierarchical structure.

Moreover, the research spans various species, demonstrating that in organisms like insects that require rapid muscle movements for flight, fluid flows within muscle fibers play a crucial role. This contrasts with larger animals where muscle contractions are primarily controlled by neural signals and molecular properties.

In essence, the study underscores the importance of considering muscle as more than a collection of molecules, but rather as a dynamic material shaped by fluid mechanics and capable of unique mechanical behaviors like odd elasticity.