Correlation between cervical flexor muscle thickness and craniocervical flexion torque in healthy subjects.

The purpose of this study was to clarify the relationship between the size of the cervical flexor muscles and craniocervical (CC) flexion torque. Thirty-eight healthy men participated in this study. Thickness of the deep cervical flexor (DCF) and sternocleidomastoid (SM) muscles were measured using ultrasonography. Maximal isometric CC flexion torque was measured using dynamometry. The DCF and SM muscle thickness and CC flexion torque were normalized relative to body weight. Correlations between normalized muscle thickness and normalized CC flexion torque were determined. A significant positive correlation was observed between normalized DCF muscle thickness and normalized CC flexion torque (r = 0.361, P = 0.028), whereas there was no significant correlation between normalized SM muscle thickness and normalized CC flexion torque (r = 0.233, P = 0.166). DCF muscle thickness appears to have potential clinical application in the performance of CC flexion.