Characterization of the Rectus Femoris Activation Patterns during Isometric Contraction in Transverse Plane: An Ultrasonography Study

Rectus femoris (RF) has long been known to be susceptible to injuries, especially in population occupationally required to stretch quadriceps forcefully. Among various RF injuries, those involve strains about the central tendon (CT) of RF are found to cost longer recovery interval than other sites. To look into the contraction pattern of RF quantitatively, we start with sonography study of CT during isometric knee extensions. Nine healthy male adults participated the experiments. The tilt angle of CT (TACT) was calculated manually. Inter-frame velocity field were computed using a Primal-Dual method. Captured at 25 Hz, totally 1920 sonograms were included in the experiments. TACT and the averaged velocity (AV) demonstrated interesting patterns in ramp increasing/ decreasing phases, compared to piece-wise quasi-linear torque signal. TACT appears sensitive to knee extension during the starting and ending phases only, which imply that during the starting and ending of torque output, CT experiences more dramatic changes of force from it two sides. The preliminary results of TACT and AV could be helpful for understanding of RF injuries during fast quadriceps stretch.