Measurement consistency of dynamic stretching muscle stiffness evaluated using shear wave elastography: comparison among different stretched levels and ROI sizes.

<bold>Aim: </bold>To investigate the reliability of quantitative analysis of dynamic stretching muscle stiffness using shear wave elas-tography (SWE), and to evaluate the influence of stretched levels and region of interest (ROI) sizes on the repeatability of SWE measurements.<bold>Materials and Methods: </bold>SWE videos of the gastrocnemius medius were collected during ankle movement from plantar flexion (PF) 40° to dorsiflexion (DF) 30°. Shear wave imageswere collected of ankle angles at PF 25°, 0°, DF 15°, and DF 30°, representing the slack status, mildly stretched level, moderately stretched level, and maximal stretched level of the gastrocnemius medius, respectively. ROI circles with diameters of 2 mm, 5 mm, and 8 mm were applied to measure the shear modulus. Intra-observer, and inter-observer repeatability of the measurements were compared among different stretched levels and ROI sizes.<bold>Results: </bold>Twenty-one healthy volunteers were enrolled. Muscle stiffness increased as the ankle DF increased. Intraclass correlation coefficients (ICCs) of intra-observer and inter-observer repeatability obtained for ROI sizes of 2 mm, 5 mm and 8 mm indicated good to excellent repeatability at all stretched levels.<bold>Conclusions: </bold>Shear wave elastography appeared to be a reliable tool to evaluate the dynamic stretching muscle stiffness with satisfactory repeatability at various stretched levels of gastrocnemius medius. Good to excellent repeatability was found using different ROI sizes. [ABSTRACT FROM AUTHOR]