Original articleSize and shape of the posterior neck muscles measured by ultrasound imaging: normal values in males and females of different ages
Introduction
Measurement of muscle size from ultrasound images can provide an objective assessment of muscle atrophy and hypertrophy (see Hides et al., 1995 and Stokes et al., 1997 for reviews). Pain, underlying pathology or injury and muscle inhibition, as well as individual muscles being part of a functional group, can prevent the assessment of muscle strength. Muscle size can provide an indirect measure of strength, as found in the neck extensors (Mayoux–Benhamou et al., 1989; Rezasoltani et al., 2002). It has also been demonstrated that resisted neck extension exercises significantly increase the strength and cross-sectional area (CSA) of the main neck extensors (Conley et al., 1997).
The cross-sectional shape of various muscles has been characterized using shape ratios based on the muscle's linear dimensions e.g. lumbar and cervical paraspinal muscles (Hides et al., 1992; Rezasoltani et al., 2002).
Two posterior neck muscles have previously been measured using ultrasound imaging, splenius capitis (Reza Soltani et al., 1996) and semispinalis capitis (Rezasoltani et al., 1998). While the posterior neck muscles are easily accessible for ultrasound imaging, no study had investigated the deep posterior neck muscles, i.e. semispinalis cervicis, multifidus and rotatores when the present study was undertaken. Recently Kristjansson (2004) has produced data on multifidus.
To assess a given muscle it is essential to know the normal values for that specific muscle. Previous ultrasound studies of the neck muscles provided normal data in relatively small numbers of normal subjects (Reza Soltani et al., 1996; Rezasoltani et al., 1998; Kristjansson, 2004). There is a need to expand normal databases and to include males and females from a wider range of ages, as recently reported for the lumbar multifidus muscle (Stokes et al., 2004).
A relationship between muscle size and anthropometric variables potentially provides a simple method of predicting normal muscle sizes and gender differences have been found (Rezasoltani et al., 1998).
The aims of the present study of the posterior neck muscles were to:
- i.
Provide normal reference ranges for size, shape and symmetry in a large sample of males and females encompassing a wide age range.
- ii.
Examine whether linear measurements relate closely enough with CSA to provide a rapid and simple means of assessing muscle size
- iii.
Examine the relationship between muscle size and body mass, body mass index (BMI) and local anthropometric variables.
Section snippets
Subjects
Muscles were scanned in 99 subjects, 46 males (aged 20–72 years) and 53 females (18–70 years). Demographic details are shown in Table 1.
Subjects were either sedentary or moderately active. Sedentary subjects were defined as having occupations involving light or no manual work and not taking part in sports. Those moderately active were in occupations involving moderate manual work but not heavy labour, and/or partaking in recreational sports up to four times a week, not competitively above club
Results
Muscle size, shape, symmetry and linear dimensions are shown in Table 2.
Discussion
The present study has provided normal reference ranges for the size and shape of the deep posterior neck and semispinalis capitis muscles, a protocol for scanning and measuring these muscles has been presented.
Conclusions
Procedures for ultrasound imaging and measurement of the posterior neck muscles at the C3 level have been described. Normal data for size, shape and symmetry of the muscles have been presented for males and females of different ages. Between-side symmetry can be used to assess abnormality of the deep neck muscle group but not semispinalis capitis.
The correlation analyses between muscle size and anthropometric measures produced only one useful regression equation, which was for predicting CSA of
Acknowledgements
The authors thank the subjects who took part in the study, the Neuro-disability Research Trust for financial support, and Dr Anthony Swan for statistical support.
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