Effects of scapular positional control on neck and upper limb muscle activity in people with and without neck pain

Abstract

Background: The concept of scapular positional control (SPC) or “scapular stabilization” has been commonly adopted as a therapeutic exercise in physiotherapy for people with neck and upper limb disorders. However, little evidence had been shown to examine the influence on the muscle activation patterns for the neck and upper limbs with this intervention. Purpose: To investigate the muscle activities of the neck and upper limb while performing typing tasks with and without maintaining the scapula in a retracted position, known as SPC, in healthy and neck pain subjects. Methods: Twenty four healthy subjects (mean age = 28.0± 4.5) who were symptom-free and fifteen neck pain subjects (mean age = 29.8± 1.7) participated in this study. Participants were instructed on how to perform and maintain the SPC action before the actual tests. Surface electromyography (EMG) was recorded while the all subjects performed two sessions of 5-min typing task with and without SPC respectively. The muscles examined were the right upper trapezius (UT), lower trapezius (LT), anterior deltoid (AD), biceps (BR), triceps (TR), flexor carpi radialis (FCR) and extensor carpi radialis (ECR). A three-dimensional motion sensor system was used to monitor the scapular position during typing. Results:The results revealed a significantly lowermedian muscle activity of UT and AD (p< 0.01) and higher median activity of LT (p< 0.01) when SPC was performed in each group. It was observed that the scapular postural angle in the transverse plane representing scapular retraction was significantly increased in the SPC condition (−23.94◦ ± 6.83 in NSPC; −8.46◦ ± 7.18in SPC; with a difference of 15.48◦ ± 2.28) in the healthy group. When these muscle activities were compared between two groups, it was found that the effect on reducing UT muscle activity during SPC in the neck pain group was significantly less compared to the healthy control group (p< 0.05). Conclusion(s): This study demonstrated that maintaining the scapula in a retracted positionwhile performing computer typing task was associated with a significant relaxation of the UT and increased activation of LT and this effect was more apparent in healthy subjects. This result suggests that the symptomatic persons need to undergo substantial training especially involving functional task simulation in order to achieve the therapeutic effects. In addition, it is also important to examine the upper limb muscle coordination which may need to be included as part of the motor control training. Implications: Motor control training involving scapular positional control should be conducted in situations involving functional tasks when managing patients with neck and shoulder disorders.