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

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.