Changes in Muscle Architecture of Vastus Lateralis Muscle during Fatiguing Contractions

[Purpose] The purpose of this study was to examine whether vastus lateralis muscle (VL) fascicle length and pennation angle alter during and after sustained submaximal isometric knee extention. [Subjects and Methods] Twelve female subjects performed maximal voluntary knee extensions (MVC) on a Biodex. This task consisted of a sustained submaximal isometric fatiguing contraction (75% MVC) until failure to hold the defined moment. Ultrasound (US) was used to visualize the muscle belly of the VL. [Results] The fascicle length of the VL decreased from 92.9 mm at the beginning to 81.3 mm at the end of fatigue, and the pennation angle increased from12.1°to14.5°. The root mean square (RMS) of the EMG signal of the VL increased signicantly with fatigue. [Conclusion] The results demonstrated that the architectural change of muscles detected using US could potentially provide complementary information for EMG for the muscle fatigue assessment.