Background: The deformation and deformation rate of the dorsal neck muscle layers in individuals with chronic whiplash associated disorders (WAD) is rarely evaluated, and the mechanical behaviour during dynamic neck extension remains to be investigated.
Purpose: To compare the deformation and deformation rate of dorsal neck muscles (trapezius, splenius capitis, semispinalis capitis and cervicis, and multifidus) in women with chronic WAD compared with healthy controls during a dynamic resisted neck extension.
Methods: Nine women with chronic grade 2 and 3 WAD (mean age 38 years, standard deviation [SD] 11.3) and nine age- and gender-matched healthy controls (mean age 38 years, SD 11.6) participated in this cross-sectional, controlled study. Ultrasonography movies and post-process speckle tracking were used to investigate real-time mechanical dorsal neck muscle behaviour at the C4 segmental level during a low-loaded dynamic standardized neck extension. Deformation (longitudinal shortening and elongation) and deformation rate (speed of deformation) were calculated during the entire exercise sequence.
Results: There were significant differences between the WAD and control groups in total deformation for the trapezius (p < 0.04) and multifidus (p < 0.03). The WAD group showed more shortening in the deformation pattern during the concentric contraction phase in the trapezius muscle, and during both the concentric and eccentric phase in the multifidus muscle compared to healthy controls. There were no other significant differences between groups either in deformation or deformation rate.
Conclusion: There were altered mechanical deformations of the trapezius and multifidus muscles, with preliminary evidence for overuse in individuals with WAD compared to healthy controls. The findings must be interpreted with caution due to the small sample size.
Implications: An ultrasound investigation made it possible to non-invasively capture multi-layered muscles in real time, adding new information of value for clinical practice of patients with WAD, which may impact future rehabilitation.
2016. Vol. 25, p. e58-