Fibre type composition of female longus capitis and longus colli muscles

Effective management of neck pain requires detailed knowledge of cervical muscle structure and function. Information on muscle fibre type assists in determining function; few data exist on the fibre type composition of many cervical muscles. The purpose of this study was to investigate the fibre type composition of longus capitis (LCa) and longus colli (LCo) to provide a better understanding of their function. Muscle sections were harvested unilaterally from LCa (C2-C7) and LCo (C3, C6, T1) in seven female cadavers (mean age 86 ± 9 years). Immunohistochemistry was used to identify type I and type II fibres, and stereology (random systematic sampling) used to determine fibre numbers. Data were assessed using descriptive statistics and one-way ANOVA (significance P < 0.05). Fifty-two sections were assessed (82,785 fibres; mean 1,592 ± 927 per section). LCa had a significantly greater proportion of type I fibres than LCo (64.3 % vs 55.7 %, P = 0.011). The percentage of fibre types varied significantly between individuals in LCa, but not LCo. No significant difference was found in the proportion of type I fibres between cervical levels for either LCa or LCo. LCa and LCo appear functionally different in elderly females, with LCa potentially having a more postural role (higher type I fibre proportion). Fibre types were homogenous throughout each muscle, indicating that contractile function is similar across the length of individual muscles. Further studies across a larger age-span and in males are required to determine whether results are representative of other populations.