Impact of Isometric Contraction of Anterior Cervical Muscles on Cervical Lordosis

Abstract

Objective: This study investigates the impact of isometric contraction of anterior cervical muscles on cervical lordosis.

Methods: 29 volunteers were randomly assigned to an anterior head translation (n=15) or anterior head flexion (n=14) group. Resting neutral lateral cervical x-rays were compared to x-rays of sustained isometric contraction of the anterior cervical muscles producing anterior head translation or anterior head flexion.

Results: Paired sample t-tests indicate no significant difference between pre and post anterior head translation or anterior head flexion. Analysis of variance suggests that gender and peak force were not associated with change in cervical lordosis. Chamberlain's to atlas plane line angle difference was significantly associated with cervical lordosis difference during anterior head translation (p=0.01).

Conclusion: This study shows no evidence that hypertonicity, as seen in muscle spasms, of the muscles responsible for anterior head translation and anterior head flexion have a significant impact on cervical lordosis.

Keywords: anterior cervical muscles; anterior head flexion; anterior head translation; cervical biomechanics; forward head posture; hypertonicity; hypolordosis; muscle spasm; neutral lateral cervical radiograph.

Figure 1

A) is an image depicting a subject positioned for the resting neutral lateral cervical (NLC) x-ray. The subject is standing in a comfortable, weight-bearing position perpendicular to the x-ray Bucky. The subject is holding the Hoggan Health microFET handheld dynamometer (Salt Lake City, UT) anterior to his head to account for the posture during isometric anterior head translation or anterior head flexion. CLA Insight™ Surface Electromyography (sEMG) sensors are attached to the anterior aspect of the neck to determine activity of the sternocleidomastoid (SCM) and cervical scalene muscles, which are responsible for anterior head translation and anterior head flexion. B) is an image depicting a subject positioned for the NLC x-ray while performing isometric anterior head translation. The subject is standing in a comfortable, weight-bearing position perpendicular to the x-ray Bucky. The subject is holding the Hoggan Health microFET handheld dynamometer (Salt Lake City, UT) against the anterior aspect of his forehead to produce isometric anterior head translation. CLA Insight™ sEMG sensors are attached to the anterior aspect of the neck to validate activity of the SCM and cervical scalene muscles, which are responsible for anterior head translation and anterior head flexion. C) is an image depicting a subject positioned for the NLC x-ray while performing isometric anterior head flexion. The subject is standing in a comfortable, weight-bearing position perpendicular to the x-ray Bucky. The subject is holding the Hoggan Health microFET handheld dynamometer (Salt Lake City, UT) against the inferior aspect of his chin to produce isometric anterior head flexion. CLA Insight™ sEMG sensors are attached to the anterior aspect of the neck to validate activity of the SCM and cervical scalene muscles, which are responsible for anterior head translation and anterior head flexion.

Figure 2

A is the Hoggan Health microFET handheld dynamometer (Salt Lake City, UT). The microFET handheld dynamometer is a Force Evaluation and Testing (FET) device. It provides objective, valid, and reliable peak force and duration of force measurements. B is the Hoggan Health microFET handheld dynamometer (Salt Lake City, UT). The microFET handheld dynamometer is a FET device. It provides objective, valid, and reliable peak force and duration of force measurements.

Figure 3

Resting NLC (left) and NLC with isometric anterior head translation (right) x-ray views of subject 14A (a 21-year-old female weighing 131 pounds). Radiographic settings include: 30 mAs, 200 mA, 68 kVp with a 72 inch focal-film distance (FFD), central ray (CR) at C4, and 7 inch by 10 inch cropping. Chamberlain’s line is the blue line originating at the posterior aspect of the hard palate and ending at the opisthion of the skull. The atlas plane line (APL) is the blue line drawn through the anterior aspect of the anterior aspect of the atlas (C1) and the vertical center of the posterior arch of C1. The red lines represent the actual posterior tangent of the cervical vertebral bodies from C2–C7 of the subject. The green line represents the ideal spinal curvature as defined by the Harrison Spinal Model. The artifacts located anterior to C3–C6 bodies are the sEMG sensors.

Figure 4

Resting NLC (left) and NLC with isometric anterior head flexion (right) x-ray views of subject 7B (a 24-year-old female weighing 101 pounds). Radiographic settings include: 30 mAs, 200 mA, 68 kVp with a 72 inch FFD, CR at C4, and 7 inch by 10 inch cropping. Chamberlain’s line is the blue line originating at the posterior aspect of the hard palate and ending at the opisthion of the skull. The APL is the blue line drawn through the anterior aspect of the anterior aspect of C1 and the vertical center of the posterior arch of C1. The red lines represent the actual posterior tangent of the cervical vertebral bodies from C2–C7 of the subject. The green line represents the ideal spinal curvature as defined by the Harrison Spinal Model. The artifacts located anterior to C3–C5 bodies are the sEMG sensors. The artifact located inferior and anterior to the chin is the dynamometer.

Figure 5

Absolute Rotational Angle from C2 to C7 (ARA C2–C7) Pre and Post Anterior Head Translation Presented is a scatter plot graph of the ARA C2–C7 for the 15 subjects in the anterior head translation group. Subjects’ assigned identification (ID) numbers are represented on the x-axis and ARA C2–C7 (°) is represented on the y-axis. The blue plots represent the resting NLC ARA C2–C7 values prior to isometric anterior head translation. The red plots represent the NLC ARA C2–C7 values during a sustained maximum isometric anterior head translation.

Figure 6

ARA C2–C7 Pre and Post Anterior Head Flexion Presented is a scatter plot graph of the ARA C2–C7 for the 14 subjects in the anterior head flexion group. Subjects’ assigned ID numbers are represented on the x-axis and ARA C2–C7 (°) is represented on the y-axis. The blue plots represent the resting NLC ARA C2–C7 values prior to isometric anterior head flexion. The red plots represent the NLC ARA C2–C7 values during a sustained maximum isometric anterior head flexion.