Russell, Matthew S.Drake, Janessa D. M.Chopp-Hurley, Jaclyn N.2026-09-112026-09-112026-04-091050-64111873-5711103157https://doi.org/10.1016/j.jelekin.2026.103157https://hdl.handle.net/10315/44055© 2026 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ).Ultrasonographic shear wave elastography is a new technique for assessing muscle stiffness in vivo. Such insights may be valuable to uncover fatigue-mediated muscle stiffness and control changes at the shoulder, for which much variability remains unexplained through EMG-based methods. This study assessed fatigue-mediated changes in shear wave velocity (SWV), EMG root-mean-squared (RMS) amplitude, EMG mean-power-frequency (MdPF), and force output from upper trapezius, middle trapezius, lower trapezius, and serratus anterior, to determine whether SWV may provide a significant predictive variance in the quantification of muscle fatigue and fatigue-mediated scapulothoracic kinematics changes. 15 males and 15 females had their scapular stabilizer muscles and scapulothoracic kinematics assessed before and after a targeted muscle fatigue protocol. Results indicate that EMG RMS amplitude and EMG MdPF were most sensitive to fatigue-mediated changes at 100% contraction intensity, while SWV appeared most sensitive at 30% and 50% contraction intensity. Scapulothoracic kinematics changes appeared most sensitive to fatigue-mediated EMG MdPF changes. These results suggest that EMG MdPF changes may be elusive in a highly redundant muscular system like the shoulder due to its association with kinematics changes altering load-sharing strategies. SWV increases at contraction intensities ≤ 50% suggest post-exercise muscle edema is a likely physiological mechanism.Print-ElectronicenAttribution-NonCommercial-NoDerivatives 4.0 Internationalhttp://creativecommons.org/licenses/by-nc-nd/4.0/Medical physiologyBiomedical and clinical sciencesHealth sciencesSports science and exerciseClinical researchRehabilitationPhysical rehabilitationPhysicalBiological and endogenous factorsMusculoskeletalHumansMuscle fatigueFemaleMuscle, skeletalMaleScapulaElasticity imaging techniquesMuscle contractionElectromyographyAdultUpper extremityShoulder jointYoung adultBiomechanical phenomenaUltrasoundStiffnessShoulderFatigueHumansMuscle FatigueFemaleMuscle, SkeletalMaleScapulaElasticity Imaging TechniquesMuscle ContractionElectromyographyAdultUpper ExtremityShoulder JointYoung AdultBiomechanical PhenomenaUpper ExtremityMuscle, SkeletalScapulaShoulder JointHumansElectromyographyMuscle FatigueMuscle ContractionAdultFemaleMaleElasticity Imaging TechniquesYoung AdultBiomechanical PhenomenaHumansMuscle FatigueFemaleMuscle, SkeletalMaleScapulaElasticity Imaging TechniquesMuscle ContractionElectromyographyAdultUpper ExtremityShoulder JointYoung AdultBiomechanical PhenomenaArticle