Activation of the serratus anterior and upper trapezius in a population with winged and tipped scapulae during push-up-plus and diagonal shoulder-elevation

Abstract

OBJECTIVES:

Scapular winging and tipping are types of abnormal scapular kinematics, which is caused by not only the entrapment of peripheral nerve, but also imbalance of the scapulothoracic musculatures. The purpose of this study was to investigate the presence of muscular imbalance in the middle and lower parts of the serratus anterior and upper trapezius in people with scapular winging and tipping.

METHODS:

Twenty male participants (age, 23.0 ± 1.92 y) were placed into symptomatic group ( $\mathit{n}=10$ ) and control group ( $\mathit{n}=10$ ). Participants completed two individual trials of a push-up plus, and a diagonal shoulder elevation, while electromyography (EMG) recorded muscle activity of the low and middle serratus anterior and upper trapezius. The root mean squared EMG values for three muscles were normalized using maximum voluntary isometric contractions (%MVIC). The value was calculated using modified isolation equation for comparing activation of middle and lower serratus anterior (%isolation).

RESULTS:

During a diagonal shoulder elevation, the % maximal voluntary isometric contraction (%MVIC) data showed that the symptomatic participants had significantly greater activation of the middle serratus anterior compared to the control group ( $\mathit{P}=0.01$ ). During a diagonal shoulder elevation, the symptomatic participants had not only significantly increased %isolation of the middle serratus anterior, but also significantly decreased for the lower serratus anterior compare with the control group ( $\mathit{p}=0.00$ ).

CONCLUSION:

Present result indicated that different muscle activation between middle and lower serratus anterior could represent in group with scapular dyskinesis, and need for selective activation of the lower serratus anterior in patients with scapular winging and tipping.