Sequential muscle activity and its functional role in the upper extremity and trunk during overarm throwing

Area of Science:

• Biomechanics
• Human Movement Science
• Sports Physiology

Background:

• The proximal-to-distal segmental sequence is recognized in sports like baseball pitching and ball kicking.
• However, the existence and functional role of sequential muscle activity in this context remain underexplored.

Purpose of the Study:

• To determine if proximal-to-distal sequential muscle activity occurs during overarm throwing.
• To elucidate the functional role of this observed muscle activation sequence.

Main Methods:

• Surface electromyograms (EMGs) were recorded from 17 upper extremity and abdominal muscles during overarm throwing.
• Muscle activation onset and peak times were analyzed to identify sequential patterns.

Main Results:

• Sequential muscle activity was observed from scapular protractors to shoulder horizontal flexors, and from shoulder horizontal flexors to elbow extensors.
• Contralateral external oblique activation preceded ipsilateral external oblique activation, suggesting trunk force generation.
• Ipsilateral external oblique activity initiated near foot strike, and rectus abdominis peaked before ball release.

Conclusions:

• Sequential muscle activation patterns exist in the upper extremity and trunk during overarm throwing.
• These sequences are likely critical for efficient force and energy transfer, contributing to high-velocity throws.
• Understanding these muscle activation dynamics can inform training and injury prevention strategies in throwing athletes.