Does vibration frequency and location influence the effect of neck muscle vibration on postural sway? A cross-sectional study in asymptomatic participants.

INTRODUCTION: Postural control is of utmost importance for human functioning. Cervical proprioception is crucial for balance control. Therefore, any change to it can lead to balance problems. Previous studies used neck vibration to change cervical proprioception and showed changes in postural control, but it remains unknown which vibration frequency or location causes the most significant effect. Therefore, this study aimed to investigate the effect of different vibration frequencies and locations on postural sway and to serve as future research protocol guidance. METHODS: Seventeen healthy young participants were included in the study. We compared postural sway without vibration to postural sway with six different combinations of vibration frequency (80, 100, and 150 Hz) and location (dorsal neck muscles and sternocleidomastoid). Postural sway was evaluated using a force platform. The mean center of pressure (CoP) displacement, the root mean square (RMS), and the mean velocity in the anteroposterior and mediolateral direction were calculated, as well as the sway area. The aligned rank transform tool and a three-way repeated measures ANOVA were used to identify significant differences in postural sway variables. RESULTS: Neck vibration caused a significant increase in all postural sway variables (p < 0.001). Neither the vibration frequency (p > 0.34) nor location (p > 0.29) nor the interaction of both (p > 0.30) influenced the magnitude of the change in postural sway measured during vibration. CONCLUSION: Neck muscle vibration significantly changes CoP displacement, mean velocity, RMS, and area. However, we investigated and found that there were no significant differences between the different combinations of vibration frequency and location.

Test - re-test reliability and concurrent validity of cervical active range of motion in young asymptomatic adults using a new inertial measurement unit device.

OBJECTIVES: Cervical range of motion (CROM) is one of the first things evaluated in cervical disorders. DyCare-Lynx is an inertial measurement unit device that was recently designed to measure CROM. Therefore, the objectives of the present study were to test the reliability and validity of the DyCare-Lynx device for active CROM. MATERIALS AND METHODS: This study included 36 healthy individuals for the reliability study and 31 individuals for the validity study. Test-retest reliability was examined in three different days, by the same examiner with a 4 ± 1-day interval between them in all cervical movements in random order. For validity, the CROM was tested with the Zebris Motion Analysis system and DyCare-Lynx simultaneously. RESULTS: The interclass correlation coefficient (ICC) of the DyCare-Lynx ranged from 0.54 to 0.90. The standard error of measurement (SEM) ranged from 2.12°-7.65°. The smallest detectable change (SDD) ranged from 11.25% to 29.75%. The Pearson's r correlation of DyCare-Lynx with Zebris ranged from 0.655 to 0.957. CONCLUSION: DyCare-Lynx showed moderate to excellent reliability and moderate-to-high validity. Moreover, SEM was low with acceptable SDD values for all movements. Overall, it can be suggested that DyCare-Lynx is a reliable and valid tool to evaluate active CROM.