Muscle as a meta-material operating near a critical point

TL;DR

This paper explores how skeletal muscles behave as meta-materials near a critical point, exhibiting unusual properties like negative stiffness and large fluctuations, due to long-range cooperative interactions.

Contribution

It reveals that muscle material operates close to a critical point, explaining its unique mechanical properties and fluctuations observed experimentally.

Findings

Muscle exhibits negative equilibrium stiffness.

Muscle operates near a critical point.

Large fluctuations observed near stall force.

Abstract

Passive mechanical response of skeletal muscles at fast time scales is dominated by long range interactions inducing cooperative behavior without breaking the detailed balance. This leads to such unusual "material properties" as negative equilibrium stiffness and different behavior in force and displacement controlled loading conditions. Our fitting of experimental data suggests that "muscle material" is finely tuned to perform close to a critical point which explains large fluctuations observed in muscles close to the stall force.