The influence of idiopathic chronic neck pain on upper trapezius and sternocleidomastoid muscle activity and elasticity during functional reaching: A cross-sectional study

It remains unclear whether idiopathic chronic neck pain is associated with changes in muscle stiffness alongside alterations in neuromuscular control. Therefore, the purpose of this study was to determine the influence of idiopathic chronic neck pain on the muscle stiffness and muscle activity of the upper trapezius and sternoclei-domastoid muscles during the maintenance of unilateral and bilateral functional reaching tasks. Surface elec-tromyography (EMG) and ultrasound shear wave elastography were collected from the sternocleidomastoid and upper trapezius muscles in 18 individuals with idiopathic chronic neck pain and 18 matched healthy controls. Participants completed three functional reaching tasks; 1) unilateral forward reach, 2) bilateral forward reach, and 3) unilateral upward reach, and held at the top of each reaching movement for data to be collected bilat-erally. A univariate ANOVA was utilized for each outcome measure (mean EMG amplitude and shear wave velocity) and each reaching task. Individuals with idiopathic chronic neck pain exhibited significantly lower upper trapezius activation during bilateral reaches without corresponding changes to stiffness during similar trials. Similarly, this cohort exhibited decreased sternocleidomastoid stiffness during forward reaching, without corresponding activation changes. Lastly, women demonstrated consistently higher sternocleidomastoid acti-vation and stiffness when compared to men. These findings indicate individuals with idiopathic chronic neck pain may adapt their movement strategies, possibly for pain avoidance. The demonstrated changes in muscle stiffness independent of changes in muscle activity highlight the importance of evaluating both muscle stiffness and activation in individuals with idiopathic chronic neck pain prior to designing rehabilitation programs.

Automated summary

This study aimed to investigate the impact of idiopathic chronic neck pain on muscle stiffness and muscle activity. The findings revealed that individuals with idiopathic chronic neck pain exhibited lower activation of the upper trapezius muscle during bilateral reaching tasks, without corresponding changes in stiffness. Similarly, these individuals showed decreased sternocleidomastoid stiffness during forward reaching, without changes in muscle activation. Additionally, women displayed consistently higher sternocleidomastoid activation and stiffness compared to men.