**5. Conclusions**

A high correlation was found between IMU and CROM for the assessment of craniocervical motion among individuals with CP and healthy subjects. However, both methods are not interchangeable. In CP subjects, the error of measurement in IMU can be considered clinically acceptable for the sagittal and frontal planes, although not for the transverse plane. When used as a reference measure for interventions, neck ROMs must achieve very high changes to ensure that the detected changes are significant. Future studies should be conducted to establish the normative data of craniocervical ROMs for specific population subgroups.

**Supplementary Materials:** Supplementary materials can be found at http://www.mdpi.com/2075-4418/10/2/80/s1.

**Author Contributions:** Conceptualization, C.C.-P., J.L.G.-C., F.A.-S., and D.P.R.-d.-S.; methodology, C.C.-P., J.L.G.-C., F.T.V., F.A.-S., and D.P.R.-d.-S.; formal analysis, J.L.G.-C. and F.A-S.; investigation, C.C.-P., F.T.V., S.A.-C., D.P.R.-d.-S., and L.G.-L.; writing—original draft preparation, C.C.-P., J.L.G.-C., F.T.V., S.A.-C., F.A.-S., D.P.R.-d.-S., and L.G.-L.; writing—review and editing, C.C.-P., J.L.G.-C., F.A.-S., and D.P.R.-d.-S.; project administration and funding acquisition, J.L.G.-C., F.A.-S., and D.P.R.-S. All authors have read and agree to the published version of the manuscript.

**Funding:** This research was funded by Consejería de Salud (Andalusian Government, Spain), grants PI-0324-2017 and PIN-0079-2016. The funding sponsor had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.

**Acknowledgments:** To the sta ff of the Rehabilitation Service of the Reina Sofía University Hospital of Córdoba (Andalusian Health Service, Spain) for their support during the recruitment of the sample and the data collection.

**Conflicts of Interest:** The authors declare no conflict of interest.
