Change in muscle viscoelasticity during static stretching

Determine how the viscoelastic properties of human skeletal muscle change during static stretching, specifically characterizing the evolution of stress-relaxation behavior and associated viscoelastic parameters over time during a sustained static stretch.

Background

The paper reviews prior work showing that stretching alters muscle properties such as passive torque, stiffness, and hardness, but notes that most studies assessed properties only before and after stretching or via indirect measures like joint range of motion, rather than continuously during the stretch. Consequently, the exact manner in which viscoelasticity changes during static stretching was not definitively established in the literature.

This paper addresses the gap by continuously measuring stress-relaxation data during static stretching, modeling the data using a fractional calculus-based spring-pot model, and reporting evidence that viscoelasticity tends to change abruptly at a particular time. The explicit open question stated by the authors concerns the general characterization of how viscoelasticity changes during static stretching.