Elsevier

Manual Therapy

Volume 15, Issue 4, August 2010, Pages 400-403
Manual Therapy

Original article
Preliminary study of neck muscle size and strength measurements in females with chronic non-specific neck pain and healthy control subjects

https://doi.org/10.1016/j.math.2010.02.010Get rights and content

Abstract

Neck muscle weakness and atrophy are two common causes of pain and disability among office workers. The aim of this study was to compare the strength of the neck extensor and flexor muscles and the size of the semispinalis capitis muscle (SECM) in patients with chronic non-specific neck pain (CNNP) and healthy subjects. Twenty female office workers (10 patients with CNNP and 10 healthy subjects) participated in this study. The strength of the neck extensor and flexor muscles was measured by an isometric device and the SECM size was measured by ultrasonography. Neck muscle strength, size of the SECM and the ratios of neck strength to body weight, neck extensor strength to SECM size, SECM size to body weight and neck flexor to extensor strength were all significantly lower in patients compared to controls (P < 0.05). In conclusion, neck strength, the size of the SECM and the ratio of neck muscle strength to SECM size appear to be useful parameters in appraising patients with CNNP.

Introduction

Neck pain is an increasing problem in society (Fejer et al., 2006). Chronic neck pain is one of the key factors for disability and discomfort in female office workers (Leijon et al., 2004, Cagnie et al., 2007). It has been reported that muscle weakness and adapting a poor or incorrect posture may be one of the main factors contributing to neck pain in office workers, especially among typists (Hagberg and Kvarnstrom, 1997, Cagnie et al., 2007).

A marked neck flexor muscles weakness has been reported in patients with mechanical neck pain when compared to healthy subjects (Silverman et al., 1991). By using an isometric device, a considerable weakness of both the neck flexor and extensor muscles has been revealed in a group of women with chronic non-specific neck pain (Ylinen et al., 2004a). Neck muscle weakness has been attributed to pain and muscle discomfort (Ylinen et al., 2004a). It is known that muscle function is disturbed in the presence of pain due to reflex inhibition (DeAndre et al., 1965, Stokes and Young, 1984).

Ultrsonography has been reported to be a reliable and feasible method to study the function of neck muscles (Rezasoltani et al., 1999, Kristjansson, 2004). DuPount et al. (2001) compared three diagnostic imaging, magnetic resonance imaging, CT scanning and ultrasonography, to measure muscle thickness. The authors reported similar results for all three methods. They stated that muscle ultrasonography was cheaper, more accessible and a noninvasive method as compared to other imaging methods. Ultrasonography studies have shown that the size of the semispinalis capitis muscle (SECM) is significantly smaller in women compared to men however no significant difference was found when muscle size was normalized for body mass (Rankin et al., 2005). In general, ultrasonography is considered to be an appropriate technique to detect muscle weakness and atrophy (Young et al., 1980, Heckmatt et al., 1988, Hides et al., 2008).

Previous studies have shown a significant correlation between the strength of the neck extensor muscles and the cross sectional area of neck semispinalis capitis muscle (Mayoux-Benhamou et al., 1989). Furthermore, a positive correlation has been reported between the cross sectional area and multiplied linear dimensions (MLD) of the neck semispinalis capitis muscle and between MLD and the strength of neck extensor muscles (Rezasoltani et al., 1998, Rezasoltani et al., 2002). MLD is calculated as the thickness or anterior–posterior dimension (APD) of the muscle multiplied by the width or lateral dimension (LD) of the muscle and is suggested to be highly reliable and less time consuming than cross sectional area measurements (Rezasoltani, 2003).

No studies have compared the strength of neck extensor muscles and the size of the semispinalis capitis muscle in patients with chronic non-specific neck pain. The present study aimed to compare the strength of the neck extensor and flexor muscles and the size (MLD) of the neck semispinalis capitis muscle between female office workers with chronic non-specific neck pain (CNNP) and a group of asymptomatic participants.

Section snippets

Methods

Twenty female office employees (10 with CNNP and 10 healthy subjects) participated in this study. They were all working in the Taleghani General Hospital, Tehran, Iran. All subjects had comparable age and working hours per day (more than 4 h with computers). All patients complained of neck pain during the last year. The exclusion criteria were as follow: any history of spinal surgery, fracture or cancer of the neck, cervical discopathy, congenital disorders of the cervical spine, traumatic

Statistical analysis

Routine statistical methods were used to determine the mean, SD (standard deviation) and the range of the measured variables. The Interclass correlation coefficient (ICC), standard error of measurement (SEM) with 95% confidence interval (95%–CI), smallest detectable difference (SDD) and Post hoc analysis (Bonforroni) were computed from one way ANOVA to detect the repeatability of neck muscle strength and muscle size measurements taken by two examiners at separate times.

An independent-samples t

Results

The mean, standard deviation and the range of anthropometric characteristics of both groups are presented in Table 1. The ICC, SEM (95%–CI) and SDD indicated a high degree of repeatability of the neck extensor strength measurements (ICC = 0.96, SEM = 3.88 N and SDD = 5.48 N), neck flexor strength measurements (ICC = 0.90, SEM = 4.58 N and SDD = 6.47 N) and neck SECM size measurements between testers (ICC = 0.90, SEM = 0.16 cm2 and SDD = 0.22 cm2).

Isometric strength of the neck extensor and

Discussion

In this study, the reliability parameters were in accordance with previous studies (Rezasoltani et al., 1998, Rezasoltani et al., 2003). The standard error of measurement (SEM) is recommended in the literature as the most important index of reliability, which quantifies error; a smaller SEM indicates a higher degree of reliability (Bland and Altman, 1996). The SDD of neck muscle strength and neck muscle size measurements in patients with chronic non-specific neck pain showed that only changes

Acknowledgment

Great thanks to subjects participated for their participation and Dr Shabestary, MD, for his kind co-operation in this study.

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