Reliability of lower leg muscle elasticity using shear wave elastography in non-weight-bearing and weight-bearing

Purpose: Muscle elasticity can be quantified with shear wave elastography (SWE) and has been used as an estimate of muscle force but reliability has not been established for lower leg muscles. The purpose of this study was to examine the intra-rater and inter-rater reliability of elasticity measures in non-weight-bearing (NWB) and weight-bearing (WB) for the tibialis anterior (TA), tibialis posterior (TP), peroneal longus (PL), and peroneal brevis (PB) muscles using SWE.Methods: A total of 109 recreationally active healthy adults participated. The study employed a single-cohort, same-day repeated-measures test-retest design. Elasticity, measured in kilopascals as the Young's modulus, was converted to the shear modulus. All four muscles were measured in NWB and at 90% WB.Results: Intra-rater reliability estimates were good to excellent for NWB (ICC = 0.930-0.988) and WB (ICC = 0.877-0.978) measures. Inter-rater reliability estimates were moderate to good (ICC = 0.500-0.795) for NWB measures and poor to good (ICC = 0.346-0.910) for WB measures.Conclusion: Despite the studies poor to good inter-rater variability, the intra-rater reproducibility represents the potential benefit of SWE in NWB and WB. Establishing the reliability of SWE with clinical and biomechanical approaches may aid in improved understanding of the mechanical properties of muscle.