J Korean Phys Ther.  2023 Oct;35(5):151-155. 10.18857/jkpt.2023.35.5.151.

Influence of Upper Trapezius and Sternocleidomastoid Muscle Activation according to Cervical Flexion Angle in Sitting Posture

• Son SM

• KMID: 2552693
• DOI: http://doi.org/10.18857/jkpt.2023.35.5.151

Abstract

Purpose
This study examined the effect of the degree of neck flexion on the muscle activity of the upper trapezius and sternocleidomastoid muscles in the sitting position.
Methods
Twenty-five healthy young adults participated in this study. The study was designed to compare the muscle activity of the upper trapezius and sternocleidomastoid muscles according to the neck flexion angle under the three conditions (neutral position, 15° neck flexion, and 45° neck flexion) in the sitting position. During the neck position of three conditions in sitting, the electromyography (EMG) data (% maximum voluntary isometric contraction) of the muscles were recorded using a wireless surface EMG system.
Results
The muscle activity of the upper trapezius muscle and the sternocleidomastoid muscles showed a significant difference according to the three-neck position conditions (p<0.05), and in the post-hoc test results, both muscles showed significant differences between the neutral position and 15° flexion, the neutral position and 45° flexion, and the 15° flexion and 45° flexion, respectively.
Conclusion
The load on the muscles around the neck and shoulders increased as the neck flexion angle increased. This suggests that performing various daily activities and tasks with the neck as neutral as possible can prevent muscle fatigue or musculoskeletal disorders.

Keyword

Upper trapezius; Sternocleidomastoid; Neck flexion; Muscle activity