Ya-Jung Lin, PT, MS1 • Huei-Ming CHai, PT, PhD2 • SHwu-Fen wang, PT, PhD3 Reliability of Thickness Measurements of the Dorsal Muscles of the Upper Cervical Spine: An Ultrasonographic Study changes during contraction to represent muscle function either using MRI or real-time ultrasonography for the cervical region. 12,13,21 Rehabilitative ultrasound imaging (RUSI) is less expensive and more mobile when compared to the "gold-standard" MRI. In addition, the clinical use of RUSI can provide for a rapid observation of muscle contraction. Change in muscle thickness has been shown to be associated with EMG signal amplitude 4,7,14 and level of contraction, 8,11,13,26 particularly during submaximal efforts. 4,7,13 A significant relationship between change in muscle thickness and EMG signal amplitude has been demonstrated for actions when the muscle acts as a prime mover 5 or at submaximal efforts. 4,7 Previous work suggests that the muscle architecture changes very little with efforts above 50% maximum voluntary isometric contraction (MVIC), 4 because additional efforts do not further stretch the tendon and surrounding connective tissue and, therefore, contribute to minimal change in muscle length or thickness. 25 Furthermore, most functional activities are performed at relatively low levels of muscular efforts. 25 Therefore, measuring the change in muscle thickness below 50% MVIC effort using ultrasonography may best represent muscle activation.RUSI measurement of the thickness R eal-time ultrasonography has been used to investigate changes in muscle morphology during contraction. The ability to quantify changes in muscle morphology to reflect muscle contraction using magnetic resonance imaging (MRI) or ultrasound imaging allows the study of the deep muscles and, in some cases, the visualization of the whole muscle, without the disadvantage t Study deSign: Clinical measurement, reliability.t ObjeCtiveS: To examine the intraday intrarater reliability of measuring thickness of the upper dorsal neck muscles at rest, as well as at 50% of maximum voluntary isometric contraction (MVIC), for upper cervical extension. t baCkgrOund: Methodology for measuring the thickness of the lower dorsal neck muscles, including semispinalis capitis and multifidus muscles, during contraction using ultrasonography has been established. Thickness measurements for the upper dorsal neck muscles have not been documented.t MetHOdS: Ten subjects (21 to 30 years of age) without neck pain and headache were recruited. Their upper dorsal neck muscles were measured both at rest and during 50% MVIC for upper cervical extension in sitting position using rehabilitative ultrasound imaging (RUSI). Muscles measured included the rectus capitis posterior major, oblique capitis superior, semispinalis capitis, and splenius capitis. All measurements were repeated after 10 minutes of rest, on the same day, by the same rater. Descriptive statistics were supplemented by calculations of intraclass correlation coefficient (ICC 3,1 ), standard error of measurement (...

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