Comparative Electromyographic Study of Scapular Muscle Activity During Scaption in Individuals With Type I AND II Scapular Dyskinesis

Aims: Scapular dyskinesis (SD) in individuals with shoulder pathologies may result from inadequate muscle performance. The variations in muscle activities among different types of SD could offer valuable insights into the development of appropriate training programs. Nonetheless, a separate analysis of muscle activities between type I and type II SD has not yet been investigated.
Method and Materials: Twenty-four volunteers with SD were randomly allocated to type I (n=12) and type II (n=12) groups in this cross-sectional study. Electromyographic (EMG) activities of the serratus anterior (SA), upper trapezius (UT), middle trapezius (MT), and lower trapezius (LT) muscles were recorded during 60° and 110° scaption tasks. Muscle activity, including maximum voluntary isometric contraction (MVIC) and root mean square (RMS), was assessed.
Findings: SA showed significantly higher activity in Group I compared to Group II at both 60° (P=0.039) and 110° (P=0.037) of scaption. MT activity was higher in Group I at 110° (P=0.035) of scaption but showed no difference at 60° (P=0.054). UT activity was significantly higher in subjects with type II SD at both 60° (P=0.046) and 110° (P=0.023), while the lower trapezius (LT) showed no significant difference at either 60° (P=0.505) or 110° (P=0.156) in both types.
Conclusion: Exercise prescriptions for type II SD should emphasize enhancing SA and MT activation more than for type I SD. Additionally, more caution should be taken to avoid excessive UT activity in Type II SD. The activity of LT should be similarly prioritized in exercise prescriptions for both types.