Original Contribution  |   June 2020
Implied Evidence of the Functional Role of the Rectus Capitis Posterior Muscles
Author Notes
• From the Department of Physical Medicine and Rehabilitation (Dr Hallgren) and the Department of Osteopathic Manipulative Medicine (Drs Hallgren and Rowan) at Michigan State University College of Osteopathic Medicine in East Lansing.
• Financial disclosures: None reported.
• Support: This study was supported in part by research grant No. 09-05-586 from the American Osteopathic Association.
•  *Address correspondence to Richard C. Hallgren, PhD, Department of Physical Medicine and Rehabilitation, Michigan State University College of Osteopathic Medicine, 909 Fee Rd, East Lansing, MI 48824-6410. Email: hallgren@msu.edu

Article Information
Original Contribution   |   June 2020
##### Implied Evidence of the Functional Role of the Rectus Capitis Posterior Muscles
The Journal of the American Osteopathic Association, June 2020, Vol. 120, 395-403.
The Journal of the American Osteopathic Association, June 2020, Vol. 120, 395-403.
Abstract

Context: Osteopathic physicians often target the rectus capitis posterior minor (RCPm) and rectus capitis posterior major (RCPM) muscles when using muscle energy or soft tissue cervical techniques to treat patients with head and neck pain. The RCPm and RCPM muscles are located deep within the posterior occipitoatlantal and atlantoaxial interspaces, respectively.

Objective: To characterize the functional role of RCPm and RCPM muscles by comparing electromyographic (EMG) activation patterns of these muscles with EMG activation patterns of specific flexor and extensor muscles of the head and neck, the sternocleidomastoid (SCM), and the splenius capitis (SC) muscles, respectively.

Methods: Asymptomatic participants were recruited from the Michigan State University College of Osteopathic Medicine student body. Disposable 25-gauge, bipolar fine-wire intramuscular electrodes were used to collect EMG data from the right and left RCPm and RCPM muscles. Surface electrodes were used to collect EMG data from the right and left SCM and SC muscles. Data were collected as participants performed 4 cycles of flexion and extension with an external 4-lb force applied to the back of the head and the forehead.

Results: In RCPM muscles, EMG activity was significantly greater (P<.003) during flexion and extension of the head and neck when an external force was applied to the back of the head. EMG activity in SCM muscles was significantly greater (P<.0001) during flexion and extension of the head and neck when an external force was applied to the forehead. The authors observed that EMG activity in SC muscles was significantly greater (P<.015) during flexion and extension of the head and neck when an external force was applied to the back of the head. No significant difference was found in EMG activity in RCPm muscles (P<.834) during flexion and extension of the head and neck, regardless of whether the external force was applied to the back of the head or the forehead.

Conclusion: The EMG activation patterns of the RCPm muscles suggest that their functional role may be to stabilize the occipitoatlantal joint by helping maintain congruency of the joint surfaces. In contrast, the EMG activation patterns of the RCPM muscles suggest that their functional role may be to contribute to extension of the head, primarily at the occipitoatlantal and the atlantoaxial joints.

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