Voluntary Abdominal Contraction During Prone Scapular Retraction Exercises

Context: Researchers have shown that scapular retraction exercises (SREs) produce greater trapezius activation in the prone than the standing position, likely due to increased gravitational load. However, the prone position requires less lumbopelvic control, potentially increasing anterior pelvic tilt and reducing scapular muscle stability. Objective: To investigate scapulothoracic muscle activation during SREs performed in the prone position while maintaining lumbopelvic stability via voluntary abdominal contraction (VAC). Design: Descriptive laboratory study. Setting: Climate-controlled laboratory. Patients or Other Participants: , Tegner activity level ≥ 5) were included. Interventions: Participants performed SREs in 4 arm positions in a randomized order with and without VAC: 0°, 45°, 90°, and 120° of abduction. Main Outcome Measures: Surface electromyographic activity was recorded for the upper trapezius, lower trapezius, and serratus anterior (SA) muscles of the dominant extremity. Results: Scapular retraction exercises elicited variable muscle activation depending on upper extremity position and VAC condition. Upper trapezius activity generally remained low to moderate across all variations, and SA activation was consistently low. Lower trapezius activity showed the most sensitivity to VAC; it increased during the eccentric phase at 0° of abduction but decreased during the concentric and isometric phases at 45° of abduction. At larger abduction angles (90° and 120°), VAC had minimal effect on upper and lower trapezius and SA activity. Overall, VAC had no meaningful effect on scapular stabilizing muscle activation. Conclusions: Voluntary abdominal contraction had minimal influence on scapulothoracic muscle activation during prone SREs, suggesting it may not be necessary for optimizing neuromuscular control in shoulder rehabilitation.