Comparison of endurance and electromyographic activity of core muscles in overhead athletes with and without scapular dyskinesis

BACKGROUND: Scapular dyskinesis (SD) is a prevalent dysfunction among overhead athletes. Although the kinetic chain emphasizes the functional linkage of the core and shoulder musculature, limited evidence exists regarding the endurance and electromyographic (EMG) characteristics of core muscles in athletes with SD. This study aimed to compare core muscle endurance and EMG activity during closed kinetic chain tasks between overhead athletes with and without SD. METHODS: Thirty female overhead athletes were divided into two groups: SD (n = 15) and without SD (n = 15), diagnosed using the Kibler lateral scapular slide test. Core endurance was assessed using the McGill Core Endurance Test, including the trunk flexor test, the trunk extensor test, and the right and left lateral plank. Surface EMG (ME6000, Finland) was used to record muscle activity of the erector spinae, multifidus, gluteus medius, transversus abdominis/internal oblique, external oblique, rectus abdominis, and serratus anterior during plank and push-up tasks. Independent t-tests and Cohen's d were used to compare groups (α ≤ 0.05). RESULTS: Athletes with SD demonstrated significantly lower endurance across all McGill tests (p ≤ 0.05, d = 0.81-0.88). EMG data showed reduced activation of the erector spinae, multifidus, gluteus medius, rectus abdominis, transversus abdominis/internal oblique, and serratus anterior muscles in the SD group during both tasks (p ≤ 0.05). No significant differences were observed in the external oblique activity. CONCLUSION: These findings highlight the importance of integrating targeted core stabilization and scapular control exercises into training and rehabilitation programs to optimize performance and prevent shoulder injuries in overhead athletes.