Scapular Muscle Activation at Different Shoulder Abduction Angles During Pilates Reformer Arm Work Exercise

Area of Science:

• Biomechanics of shoulder joint motion.
• Exercise physiology and muscle activation.
• Kinesiology of scapular stabilization.

Background:

• Scapular muscles are vital for shoulder stability and injury prevention during arm movements.
• Shoulder abduction angle significantly influences scapular muscle engagement.
• Pilates reformer arm work (AW) offers varied shoulder abduction angles for exercise.

Purpose of the Study:

• To investigate the effect of different shoulder abduction angles on scapular muscle activation during AW.
• To identify optimal angles for selective muscle engagement in Pilates exercises.

Main Methods:

• Twenty-six healthy males performed AW at 0°, 90°, 135°, and 160° shoulder abduction angles.
• Surface electromyography measured activation of upper trapezius (UT), middle trapezius (MT), lower trapezius (LT), serratus anterior (SA), posterior deltoid (PD), and levator scapulae (LS).
• Muscle activation ratios (UT/LT, LS/LT, UT/SA, LS/SA) were analyzed.

Main Results:

• Upper trapezius (UT), lower trapezius (LT), and serratus anterior (SA) activation increased with shoulder abduction angle.
• Peak activation for LT occurred at 135°, while MT and PD peaked at 90°.
• Specific muscle activation ratios varied significantly across different abduction angles, with lowest ratios observed at 90°, 135°, and 160°.

Conclusions:

• Shoulder abduction angle critically influences scapular muscle recruitment during AW.
• Targeted shoulder abduction angles can selectively activate specific scapular muscles.
• Findings provide evidence for optimizing Pilates AW exercises to enhance scapular control and stability.