Muscle stress provides a lower bound on the magnitude of shear wave velocity

It is currently unclear whether shear wave velocity (SWV) is able to predict changes in muscle stiffness independent of changes in stress, as these covary in muscle and SWV is known to depend on both stress and the material properties of a tissue. Our unique animal model allowed us to match ultrasound estimates of SWV with direct mechanical measures of muscle stress and stiffness in a passive and active muscle. We found that muscle stress alone can predict SWV in passive muscle, and that activation increases SWV beyond the estimate made considering only stress. These results demonstrate the importance of considering the full state of a muscle when trying to interpret the results from shear wave elastography.