Background The craniocervical flexion test (CCFT) is recommended when examining patients with neck pain related conditions and as a deep cervical retraining exercise option. During the execution of the CCFT the examiner should visually assess that the amount of craniocervical flexion range of motion (ROM) progressively increases. However, this task is very subjective. The use of inertial wearable sensors may be a user-friendly option to measure and objectively monitor the ROM. The objectives of our study were (1) to measure craniocervical flexion range of motion (ROM) associated with each stage of the CCFT using a wearable inertial sensor and to determine the reliability of the measurements and (2) to determine craniocervical flexion ROM targets associated with each stage of the CCFT to standardize their use for assessment and training of the deep cervical flexor (DCF) muscles. Methods Adults from a university community able to successfully perform the CCFT participated in this study. Two independent examiners evaluated the CCFT in two separate sessions. During the CCFT, a small wireless inertial sensor was adhered to the centre of the forehead to provide real-time monitoring and to record craniocervical flexion ROM. The intra- and inter-rater reliability of the assessment of craniocervical ROM was calculated. This study was approved by the Research Ethics Committee of CEU San Pablo University (236/17/08). Results Fifty-six participants (18 males, 23 females; mean [SD] age, 21.8 [3.45] years) were included in the study and successfully completed the study protocol. All interclass correlation coefficient (ICC) values indicated good or excellent reliability of the assessment of craniocervical ROM using a wearable inertial sensor. There was high variability between subjects on the amount of craniocervical ROM necessary to achieve each stage of the CCFT. Conclusions The use of inertial sensors is a reliable method to measure the craniocervical flexion ROM associated with the CCFT. The great variability in the ROM limits the possibility to standardize a set of targets of craniocervical flexion ROM equivalent to each of the pressure targets of the pressure biofeedback unit.

BACKGROUND The use of wearable inertial sensors has shown to be an easy-to-use and reliable option to objectively measure and monitor the range of motion (ROM) associated with each stage of the craniocervical flexion test (CCFT). However, previous research showed limitations when discriminating between each of the stages of the CCFT to standardize a set of ROM targets, since the instrumentation used only provided data of ROM on each of six pressure stages of the CCFT and the process of associating values of ROM and pressure was not automatically synchronized by a computer. OBJECTIVE The aim of the study is to develop a novel real-time, high-precision (Computer-based) time synchronization system to continuously record pressure and craniocervical flexion ROM during the CCFT in order to assess its feasibility on measuring and discriminating the values of ROM between different pressure levels. METHODS This is a descriptive, observational, cross-sectional study in a sample of asymptomatic participants in order to allow for the description of normative values of ROM and pressure during an ideal execution of the CCFT. All participants performed a testing procedure consisting on the performance of full-range craniocervical flexion and the CCFT. During the CCFT, a low-range pressure sensor and a wireless inertial sensor simultaneously registered data of pressure and ROM. A web application was developed using HTML and NodeJS technologies. It allowed for real-time synchronization of processing, visualization, and storage of data from both sensors at a frequency of 50Hz. A biofeedback computer screen allowed for real-time observation and assessment of the correct performance of the CFFT for both the examiner and the patient by observing pressure and ROM graphics at the same time. RESULTS A total of 45 participants successfully finished the study protocol (20 males, 25 females; mean [SD] age, 32 [11.48] years). One-way analyses of variance (ANOVAs) showed large effect significant interactions between pressure levels and the percentage of full craniocervical flexion ROM when considering the 6 pressure reference levels of the CCFT (P<0.001; η2=0.697), 11 pressure levels separated by 1 mmHg (P<0.001; η2=0.683) and 21 pressure levels separated by 0.5 mmHg (P<0.001; η2=0.671). Curve estimation regression analysis showed a significant curvilinear relationship (quadratic model) between pressure and ROM both measured in percentage (R=.811; P<.001) and in degrees (R=.805; P<.001). CONCLUSIONS The novel time synchronizing system developed in this study seems a feasible option for future research and clinical practice to provide real-time monitoring of both pressure and ROM through a computer screen high-precision feedback during the performance of the CCFT. The values of craniocervical flexion ROM presented in this study could serve as reference targets to further investigate the potential use of inertial sensor technology to assess or train deep cervical flexors. CLINICALTRIAL Not applicable

IntroductionNeck pain is a very common musculoskeletal disorder associated with high socioeconomic costs derived from work absenteeism and medical expenses. Previous studies have suggested that patients with neck pain of different origins present sensorimotor control impairments compared with the asymptomatic population. However, there is a small number of published studies focusing on these with conflicting results. In addition, the existing methodological limitations highlight the need for more and better quality studies. Moreover, longitudinal studies are necessary to investigate whether changes in pain or disability in individuals with chronic neck pain over time associate with changes in cervical sensorimotor control.Methods and analysisThis is a descriptive, observational, longitudinal, prospective study consecutively enrolling 52 patients with non-specific neck pain and 52 age-matched asymptomatic participants.Intensity of pain, neck disability, duration of symptoms, topography of pain and comorbidities will be registered at baseline. Sensorimotor control variables including active range of motion, movement speed, acceleration, smoothness of motion, head repositioning accuracy and motion coupling patterns will be recorded as primary outcomes by means of inertial sensors during the following tests consecutively performed in two sessions separated by 12 months: (1) kinematics of planar movements, (2) kinematics of the craniocervical flexion movement, (3) kinematics during functional tasks and (4) kinematics of task-oriented neck movements in response to visual targets.Secondary outcomes will include: (1) Regular physical activity levels, (2) Kinesiophobia, (3) Symptoms related to central sensitisation and (4) The usability of the inertial measurement unit sensor technology.Ethics and disseminationThis study was approved by the Research Ethics Committee of CEU San Pablo University (495/21/39). Patients will be recruited after providing written informed consent and they will be able to withdraw their consent at any time. Only the study investigators will have access to the study data. The results will be disseminated through scientific publications, conferences and media.Trial registration numberNCT05032911.

The aim of the study was to develop a novel real-time, computer-based synchronization system to continuously record pressure and craniocervical flexion ROM (range of motion) during the CCFT (craniocervical flexion test) in order to assess its feasibility for measuring and discriminating the values of ROM between different pressure levels. This was a descriptive, observational, cross-sectional, feasibility study. Participants performed a full-range craniocervical flexion and the CCFT. During the CCFT, a pressure sensor and a wireless inertial sensor simultaneously registered data of pressure and ROM. A web application was developed using HTML and NodeJS technologies. Forty-five participants successfully finished the study protocol (20 males, 25 females; 32 (11.48) years). ANOVAs showed large effect significant interactions between pressure levels and the percentage of full craniocervical flexion ROM when considering the 6 pressure reference levels of the CCFT (p < 0.001; η2 = 0.697), 11 pressure levels separated by 1 mmHg (p < 0.001; η2 = 0.683), and 21 pressure levels separated by 0.5 mmHg (p < 0.001; η2 = 0.671). The novel time synchronizing system seems a feasible option to provide real-time monitoring of both pressure and ROM, which could serve as reference targets to further investigate the potential use of inertial sensor technology to assess or train deep cervical flexors.

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