Shoulder muscle activation during scapular protraction exercise with arm rotation.

Area of Science:

• Biomechanics
• Exercise Physiology
• Musculoskeletal Anatomy

Background:

• The serratus anterior muscle is crucial for scapular stability.
• Scapular protraction exercises are commonly used to strengthen the serratus anterior.
• Optimal arm rotation during these exercises is often not specified.

Purpose of the Study:

• To determine if incorporating arm external rotation affects serratus anterior muscle activation during protraction exercises.
• To compare muscle activations under different arm rotation conditions.

Main Methods:

• Thirty-four healthy males performed scapular protraction exercises in standing and supine positions at 90° and 120° shoulder flexion.
• Exercises were conducted with the arm in a neutral (thumb-up) or externally rotated position.
• Serratus anterior muscle activity was quantified using %MVC (percentage of maximum voluntary contraction).

Main Results:

• Arm external rotation significantly increased middle and lower serratus anterior activity compared to the neutral position across all tested conditions.
• The highest muscle activations for both middle and lower serratus anterior were recorded during 120° shoulder flexion in standing with arm external rotation.

Conclusions:

• Performing scapular protraction exercises with arm external rotation enhances serratus anterior muscle activation.
• This technique modification may offer a more effective method for strengthening the serratus anterior and improving scapular stability.