Reliability of a measurement of neck flexor muscle endurance.
BACKGROUND AND PURPOSE
Neck flexor muscle endurance has been negatively correlated with cervical pain and dysfunction. The purposes of this study were to determine rater reliability in subjects both with and without neck pain and to determine whether there was a difference in neck flexor muscle endurance between the 2 groups.


SUBJECTS
Forty-one subjects with and without neck pain were enrolled in this repeated-measures reliability study.


METHODS
Two raters used an isometric neck retraction test to assess neck flexor muscle endurance for all subjects during an initial session, and subjects without neck pain returned for testing 1 week later.


RESULTS
For the group without neck pain, intrarater reliability was good to excellent (intraclass correlation coefficient [ICC(3,1)]=.82-.91), and interrater reliability was moderate to good (ICC[2,1]=.67-.78). The associated standard error of measurement (SEM) ranged from 8.0 to 11.0 seconds and from 12.6 to 15.3 seconds, respectively. For the group with neck pain, interrater reliability was moderate (ICC[2,1]=.67, SEM=11.5). Neck flexor muscle endurance test results for the group without neck pain (mean=38.95 seconds, SD=26.4) and the group with neck pain (mean=24.1 seconds, SD=12.8) were significantly different.


DISCUSSION AND CONCLUSION
Reliability coefficients differed between the 2 groups and ranged from moderate to excellent and improved after the first test session. The interrater reliability of data obtained with the neck flexor muscle endurance test in people with neck pain must be improved in order for clinicians to distinguish a clinically meaningful change from measurement error. Neck flexor muscle endurance was both statistically and clinically greater for subjects without neck pain than for those with neck pain.