Test-retest reliability of cervicocephalic kinesthetic sensibility in three cardinal planes

The test-retest reliability of both the head-to-neutral head position (NHP) and head-to-target repositioning tests in three cardinal planes has been examined in this study. Twenty young adults underwent both head repositioning tests and retests with 10 min rest intervals. Root mean square error (RMSE, total error), constant error (CE, directional bias), variable error (VE, variability), and standard error of measurement (SEM) were calculated from the position data recorded by an ultrasound-based motion analysis system. Intra-class correlation coefficients (ICC) were used to examine reliability. The results showed fair to excellent reliability of RMSE during head-to-NHP (ICC=0.45-0.80) and head-to-target tests (ICC=0.42-0.90), except during the head-to-NHP test (ICC=0.29) from a head extended position. Low reliability of VE associated with the neck motion toward left side bending indicated a direction-dependent effect. The SEM of RMSE (0.7-2.6 degrees), CE (0.3-4.0 degrees) and VE (0.4-1.5 degrees) indicated an acceptable range of error. The present study indicated acceptable and reliable RMSE measurements with a motion analysis system in healthy young adults. Furthermore, examining the CE and VE could contribute to the interpretation of whether the subject performed the reposition tests with directional bias and repositioning variability, respectively.