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Correlation between contraction ratio, endurance, and muscle tone of cervical muscles
Physical Therapy Rehabilitation Science 2020;9:302-8
Published online December 30, 2020
© 2020 Korean Academy of Physical Therapy Rehabilitation Science.

Ji-Hee Hong , Dong-Hyeon Lee , Seong-Eun Kim , Dong-kwon Seo

Department of Physical Therapy, Konyang University, Daejeon, Republic of Korea
Correspondence to: Dong-kwon Seo (ORCID
Department of Physical Therapy, Konyang University, 158 Gwanjeodong-ro, Seo-gu, Daejeon 35365, Republic of Korea
Tel: 82-42-600-8457 Fax: 82-42-600-8408 E-mail:
Received August 31, 2020; Revised September 24, 2020; Accepted September 28, 2020.
cc This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Objective: The endurance and strength of deep neck flexor (DNF) muscles have a major role on the function and stability of the cervical spine. In recent years, there has been a lack of research that have investigated the muscle tone of the superficial neck muscles. The purpose of this study was to examine the relationship of between contraction ratio of the DNF and sternocleidomastoid (SCM) muscles, DNF endurance, and muscle tension of the neck muscles.
Design: Cross-sectional study.
Methods: Forty-seven subjects (male=20, female=27) participated in this study. The muscle tone of the upper trapezius (UT), SCM, and suboccipital (SO) muscle was measured using a contact soft tissue tone-measuring instrument. For the contraction ratio of the SCM and longus colli muscle, the thickness of the relaxation and maximum contraction state of the SCM and longus colli muscles were assessed using a diagnostic ultrasound measuring instrument and a pressure biofeedback unit. The deep neck flexor endurance test (DNFET) was performed in a cranio-cervical flexion posture. The correlations between the measured variables were investigated.
Results: The relationship between the DNFET and SO tone showed a significant negative correlation (p<0.05). The relationship between the DNFET and contraction ratio showed a significant positive correlation (p<0.01). There was no significant correlation between the DNFET and SCM and UT tone.
Conclusions: This study confirmed that there is a relationship between DNF endurance, DNF activation, and SO tone. The information on the results of this study may be used as a reference that can be actively applied in the clinical environment.
Keywords : Endurance, Muscle tonus, Neck muscle, Ultrasonography


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