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Hazaki K.1, Miyata N.2
1Osaka Electro-Communication University, Shijonawate, Japan, 2Nagayoshi General Hospital, Osaka, Japan
Background: The longus colli (LC) muscle runs from the anterior aspect of C1 through T3 as a deep cervical flexor, and provides cervical spine stability. The standard assessment of the LC is the craniocervical flexion test (CCFT), which is performed with the subject supine. However, instability of the cervical spine becomes a problem when standing or sitting, because the head must maintain a vertical position against gravity.
Purpose: The present study aimed to determine the activity of the LC and sternocleidomastoideus (SCM) muscles by measuring muscle thickness during the CCFT when performed with the subject sitting.
Methods: Muscle thicknesses of the LC and SCM in 16 healthy men (mean age, 20.2 ± 0.9 years) were measured on the right side using ultrasonography (US) with a 10-MHz linear array probe placed parallel to the vertical axis running external to and 2 cm inferior from the thyroid cartilage and tilted 20° inward in the median sagittal plane. Subjects were seated in an upright position with the scapula and sacrum contacting the wall, and the hips and knees bent 90°. CCFT was performed using a Stabilizer TM (Chattanooga Group Inc.). An air-filled pressure sensor was placed suboccipitally behind the neck of the subject and inflated to a baseline pressure of 20 mmHg, sufficient to fill the space between the back of neck and the wall. During CCFT, subjects were instructed in the action of craniocervical flexion and pressure was increased in 2-mmHg increments with a final pressure target of 28 mmHg. In each stage, subjects performed the action and held the target pressure for 10 s while US images of the LC and SCM were acquired. Thicknesses of the LC and SCM muscles were measured on US images using ImageJ image analysis software. Whether or not significant differences in muscle thicknesses of the LC and SCM existed between stages of CCFT were determined by repeated one-way ANOVA and Fisher´s LSD test.
Results: For LC, ANOVA showed a significant effect of CCFT stage (F= 2.63, p 0.05). Fishers LSD revealed significant differences between 20 mmHg and 24 mmHg (p 0.05), and 26 mmHg (p 0.05). For SCM, the ANOVA did not show a significant effect of CCFT stage.
Conclusion(s): In previous studies that performed CCFT in the supine position, LC significantly increased the muscle thickness with an increasing stepwise load, whereas in the present study it significantly increased with a relatively weak load (24 mmHg and 26 mmHg). This fact was attributed to the fact that cervical extensor muscle is under higher tension when sitting than when supine, and the fact that cervical lordosis is difficult to decrease. In other words, the decrease of cervical lordosis reaches a limit under weak loads.
Implications: When performing muscle training for LC in a sitting position, exercise intensity should generally be kept low.
Funding acknowledgements: Nothing
Topic: Outcome measurement
Ethics approval: The ethics review board for studies involving living bodies at Osaka Electro-Communication University approved this study (14-007).
All authors, affiliations and abstracts have been published as submitted.
