Intrarater and Inter-rater Reliability of Maximal Voluntary Neck Muscle Strength Assessment Using a Handheld Dynamometer in Women With Headache and Healthy Women

Objective: This study aimed to determine the inter-rater and intrarater reliability, agreement, and minimal detectable change (MDC) of the neck muscle strength test using a handheld dynamometer in healthy women and women with headaches. Methods: Neck muscle strength in maximal voluntary contraction was measured using the Lafayette Manual Muscle Testing attached to a nonelastic belt in 25 women with migraines and in 25 healthy women. Three repetitions of flexion, extension, and lateral flexion were performed. The tests were performed by 2 examiners on the same day, with a 10-minute interval, and by 1 examiner, with a 1-week interval. The reliability was verified by the intraclass correlation coefficient, the agreement determined by standard error measurement, and the MDC calculated. Results: The protocol exhibited moderate to excellent intrarater and inter-rater reliabilities in both groups (intraclass correlation coefficient(range, ) 0.53-0.90). The standard error measurement ranged from 0.43 to 1.81 and the MDC from 1.49 up to 4.61. Conclusion: Quantification of neck muscle strength using the handheld dynamometer with an attached nonelastic belt exhibited moderate to excellent intra- and inter-rater reliability in women with and without migraines. Moreover, the standard error measurement and MDC were proven to be useful in the interpretation of data and in guiding clinical decisions. (AU)