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"Avatar", a Modified Ex vivo Work Loop Experiments Using In vivo Strain and Activation
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Length and activation dependent variations in muscle shear wave speed.
L A Chernak1, R J DeWall, K S Lee
1University of Wisconsin-Madison, 3046 Mechanical Engineering, 1513 University Ave, Madison, WI 53706 USA. lchernak@wisc.edu
Physiological Measurement
|May 31, 2013
Summary
Shear wave elastography (SWE) can measure muscle stiffness changes during active and passive movements. Results show SWE is promising for assessing muscle loading, but active versus passive conditions affect measurements differently.
Area of Science:
- Biomechanics
- Medical Imaging
- Musculoskeletal Research
Background:
- Clinical assessment of muscle stiffness is limited by cost and availability.
- Muscle stiffness varies with disease states and mechanical loading.
- Shear wave elastography (SWE) offers a non-invasive method to quantify tissue mechanical properties.
Purpose of the Study:
- To investigate the capability of SWE to measure gastrocnemius muscle shear wave speed variations.
- To assess SWE's response to active muscle contraction and passive stretch.
- To evaluate SWE as a tool for quantifying in vivo muscle mechanical loading.
Main Methods:
- Ten healthy adults participated in the study.
- SWE measurements were taken on the medial gastrocnemius at various ankle angles (passive stretch).
- SWE measurements were also recorded during voluntary plantarflexor contractions (active loading).
Main Results:
- Shear wave speed increased significantly with passive dorsiflexion in an extended knee posture (2.6 to 5.6 m/s).
- Passive stretch did not affect shear wave speed when the gastrocnemius was shortened (flexed knee).
- Active contractions showed a monotonic relationship between shear wave speed and ankle moment, reaching 8.3 m/s.
- A linear correlation between shear wave speed and ankle moment was observed in both active and passive conditions, with a steeper slope for passive loading.
Conclusions:
- SWE is a promising technique for quantitatively assessing in vivo muscle mechanical loading.
- The differential response of SWE to active versus passive loading necessitates careful consideration of measurement conditions.
- Further research is needed to optimize SWE protocols for characterizing muscle properties under different loading scenarios.
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