Study design: Clinical measurement, reliability.
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.
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.
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 (ICC3,1), standard error of measurement (SEM), within-subject coefficient of variation (CVw), and minimal detectable change (MDC).
Results: ICC3,1 results ranged from 0.87 to 0.99 for thickness measurements made at rest and from 0.90 to 0.98 for thickness measurements made with a 50% MVIC. The SEMs for thickness measurements at rest and at 50% MVIC ranged from 0.11 to 0.46 mm and 0.23 to 0.52 mm, while the CVws ranged from 3.5% to 6.1% and 3.7% to 6.4%, and MDC95 ranged from 0.35 to 1.46 mm and 0.73 to 1.65 mm, respectively. The thickness of all upper dorsal neck muscles measured during a 50% MVIC was greater than when measured at rest (P<.029).
Conclusion: Thickness measurements of the upper dorsal neck muscles using RUSI were reliable both at rest and during a 50% effort isometric contraction.