Difference in fascicle behaviors between superficial and deep quadriceps muscles during isometric contractions

ABSTRACT Introduction In this study we examined changes in fascicle length and pennation of vastus intermedius (VI) and vastus lateralis (VL) from rest to isometric contraction. Methods Fourteen healthy men performed submaximal (30% and 50% of maximal voluntary contraction; MVC) isometric knee extensions at 60° and 110° knee flexion (0° = full extension). Panoramic images of VL and VI were obtained at rest and during contractions to measure fascicle length and pennation using extended field‐of‐view ultrasonography, after confirmation that the technique could be used reliably during sustained submaximal isometric contractions. Results The relative change in fascicle length from rest to 50% MVC was greater in VI than VL at 110° (P