“…Traditional grey scale ultrasound, which has been used in previous studies of neck muscles (Rezasoltani et al, 1998(Rezasoltani et al, , 1999(Rezasoltani et al, , 2002Kristjansson, 2004;Rankin et al, 2005;Fernández-De-Las-Peñas et al, 2008;Jesus et al, 2008;Lee et al, 2009), provides information about anatomical landmarks and structural information about the tissue. Dorsal (Lee et al, 2007(Lee et al, , 2009) and ventral (Jesus et al, 2008) neck muscles have been studied using changes in muscle thickness or cross-sectional area (CSA) as an indication of muscle activity. Lee et al (2007Lee et al ( , 2009) studied the CSA of the multifidus muscle during rest and isometric head extension, finding that ultrasound can detect changes in multifidus during contraction, with acceptable reliability.…”