Briefly, after determining the measurement sites and coating them withwater-soluble transmission gel to aid optimum acoustic coupling, the probe was placed perpendicularly to the
specific muscle to observe a cross-sectional image to measure the muscle thickness. After imaging and marking the images for later analyzing, the probe was placed at the same point and parallel to the specific muscle resulting in a longitudinal image to measure the pennation angle. The muscle thickness was defined as the distance between the
superficial and deep aponeurosis of the muscle in the cross-sectional image (Figure 1; left). The pennationangle was measured as the acute angle of insertion of
muscle fiber fascicles into the deep aponeurosis in the longitudinal image (α in Figure 1; right). Finally, fascicle length was estimated by the following geometric formula
(L in Figure 1; right):