"Comparison of Upper and Lower Trapezius Muscle Activity during Arm Lift Exercise with and without Pressure Biofeedback"

Background Excessive muscle activation of the upper trapezius and decreased muscle activation of the lower trapezius can lead to changes in scapulohumeral rhythm. Many studies suggest that arm lift exercises are known to selectively strengthen the lower trapezius muscle. However, there has been no study on how compensatory actions, such as trunk rotation during arm lifting, affect the muscle activation of the upper and lower trapezius muscles. Objectives The study investigated the effect of pressure biofeedback on the muscle activity of the upper and lower trapezius muscles and the trunk rotation angle during arm lift exercises. Methods A total of 15 healthy adults were recruited for this study. Muscle activity of the upper and lower trapezius, as well as the trunk rotation angle, were measured during arm lift exercise with and without pressure biofeedback. Trunk rotation angles were analyzed using the Kinovea® program. Muscle activity of the upper and lower trapezius muscles and trunk rotation angle during the arm lift exercise with and without pressure biofeedback were statistically analyzed using paired t-test. Results With pressure biofeedback, upper trapezius muscle activity significantly decreased compared to without pressure biofeedback (p < 0.001). In contrast, lower trapezius muscle activity significantly increased during the arm lift exercise with pressure biofeedback compared to without pressure biofeedback (p = 0.002). Additionally, the trunk rotation angle significantly decreased with pressure biofeedback compared to without pressure biofeedback (p < 0.001). Conclusions Applying pressure biofeedback during arm lift exercise can effectively enhance the selective strength of the lower trapezius muscle by minimizing compensatory actions such as trunk rotation. This method has proven to be effective in strengthening the lower trapezius.