Muscle physiology: Brief report
The variation of the strength of neck extensor muscles and semispinalis capitis muscle size with head and neck position

https://doi.org/10.1016/j.jbmt.2012.07.001Get rights and content

Summary

Semispinalis capitis muscle (SECM) is a massive and long cervico-thoracic muscle which functions as a main head and neck extensor muscle. The aim of this study was to detect the effect of head and neck positions on the strength of neck extensor muscles and size of SECM in healthy subjects. Thirty healthy women students voluntarily participated in this study. An ultrasonography apparatus (Hitachi EUB 525) and a system of tension-meter were used to scan the right SECM at the level of third cervical spine and to measure the strength of neck extensor muscles at three head and neck positions. Neck extensor muscles were stronger in neutral than flexion or than extension positions while the size of SECM was larger in extension than neutral or than flexion position. The force generation capacity of the main neck extensor muscle was lower at two head and neck flexion and extension positions than neutral position.

Introduction

The strength of a group of neck muscles varies according to the joint range of motion. By using an isometric muscle strength test Vasavada et al. reported that the strength of neck extensor muscles were the strongest while head and neck were in neutral position. The authors concluded that the force generation capacity of neck extensor muscles was not constantly maintained during the entire cervical range of motion (Vasavada et al., 1998). The function of an individual muscle may also be varied during an entire range of motion accordingly. Ultrasonography has been recommended to study the function of a single small muscle even located in deep layers (Rezasoltani et al., 2002; Lee et al., 2009; Javanshir et al., 2011).

In an ultrasonography study, Wantanabe et al. measured the thickness of the lumbar extensor muscles when subjects were in different positions of the lumbar spine (standing neutral, flexion and extension) (Watanabe et al., 2004). The authors reported that muscles thickness was the largest in the lumber extension position and the smallest at in the lumbar flexion position. McGill et al. combined two methods of muscle strength test and muscle ultrasonography and revealed that the force generation capacity and the dimension of erector spinae muscles decreased when subjects were in a lumbar flexion position (McGill et al., 2000).

The strength related neck muscle size in different ranges of head and neck position have not yet been reported. The study of the function of the neck semispinalis capitis muscle (SECM) is very important since it acts as a prime mover and main head and neck extensor muscle. The aim of this study was to detect the effect of head and neck positions on the strength of neck extensor muscles and size of SECM in healthy subjects.

Section snippets

Methods

Thirty healthy female students (age 18–24 years old) voluntarily participated in this study. They were informed about the aim and experimental aspects of the research prior to the study. The study protocol was approved by the Ethical Committee of Shahid Beheshti University of Medical Sciences.

A real time ultrasonography device (Hitachi EUB 525, Japan) with the frequency of 7.5 MHz linear array probe was applied in this study. The subjects were asked to sit relaxed, on a chair without back

Statistical analysis

To estimate the repeatability of the measurements taken by two examiners, the ICC (Intra-class coefficient correlation) was computed from repeated measurement of ANOVA. A one-way analysis of variance was used to compare any difference in variables of muscles strength and muscle size among positions of neutral, flexion and extension. The statistical analysis was performed using the SPSS statistical software program for Windows.

Results

The index of inter-testers reliability for SECM size measurement was 0.88 < ICC < 0.98 and for muscle strength measurements it was 0.75 < ICC < 0.90 in all three positions. The size of SECM was significantly smaller in flexion than extension (p < 0.001) (Fig. 1). The maximum isometric strength of neck extensor muscles was significantly different between extension and flexion positions and also between extension and neutral positions (p < 0.05) (Table 1). Indicating that, neck extensor muscles

Conclusion

The size and the strength of a muscle may linearly be associated with the joint range of motion (Vasavada et al., 1998; McGill et al., 2000; Watanabe et al., 2004). The authors of two earlier studies stated that lumbar flexion caused a reduction in dimensions of erector spinae muscles (McGill et al., 2000; Watanabe et al., 2004). In our study, the size of SECM was larger in extension than that of flexion position. The difference may be related to the variation of SECM length from extension to

Conflict of interest statement

The Authors certify that there is no actual or potential conflict of interest in relation to this article.

Acknowledgments

The authors of this study would like to thanks to all of the subjects who participated in this study and to Dr Faizei (MD) for his kind cooperation, arrangements and attitude toward this study.

References (12)

There are more references available in the full text version of this article.

Cited by (10)

  • The Effects of Forward Head Posture on Neck Extensor Muscle Thickness: An Ultrasonographic Study

    2018, Journal of Manipulative and Physiological Therapeutics
    Citation Excerpt :

    The measurements were carried out using Autocad Software Version 12 (Autodesk, San Rafael, California).25 A Multi-Analyzer Myometer (MIE Medical Research Ltd., Leeds, United Kingdom) was utilized to assess the MVIC of the neck extensor muscles.12 Participants were instructed to sit relaxed on a chair while putting their hands on their legs and keeping their heads and necks in neutral position.

  • The relationship between RMS electromyography and thickness change in the skeletal muscles

    2017, Medical Engineering and Physics
    Citation Excerpt :

    Jun et al. [5] has shown that there is an exponential relationship between the normalized EMG and the deformation of the biceps brachii muscle. Rezasoltani et al. [25,26] has shown an increasing of semispinalis capitis muscle thickness during the isometric neck extension and dimension changes of these muscle during cervical flexion and extension. Also changes in the muscles thickness during different activities have been reported for several cervical muscles [27–30].

View all citing articles on Scopus
View full text