Changes in shear wave propagation within skeletal muscle during active and passive force generation

Area of Science:

• Biomechanics
• Musculoskeletal Research
• Medical Imaging

Background:

• Muscle force generation involves both active (neural excitation) and passive (length changes) components.
• Disruptions in muscle force generation due to disease or injury make it difficult to differentiate active from passive contributions.
• Ultrasound elastography is a valuable tool for assessing muscle mechanical properties and forces.

Purpose of the Study:

• To investigate if phase velocity measurements can differentiate active from passive muscle force generation.
• To compare shear elasticity estimates derived from group versus phase velocity.
• To explore the utility of a Voigt model in characterizing muscle viscoelasticity.

Main Methods:

• Measured phase and group velocity of shear waves in the human biceps brachii.
• Quantified shear elasticity using both group and phase velocity measurements.
• Applied a Voigt model to characterize phase velocity and identify time constants.

Main Results:

• Group velocity measurements consistently overestimated muscle shear elasticity.
• Phase velocity analysis, using a Voigt model, revealed distinct characteristics for active and passive force generation.
• The estimated time constant from the Voigt model effectively distinguished between active and passive conditions.

Conclusions:

• Shear wave elastography, by analyzing phase velocity, can differentiate between active and passive muscle force generation.
• Phase velocity provides unique insights into muscle viscoelastic properties not captured by group velocity alone.
• This technique offers a promising non-invasive method for evaluating muscle function in health and disease.