Maxwell Skene

Abstract

Background: Baseball pitching is a biomechanically complex, high-velocity movement that places substantial demands on the upper extremity. Inefficient coordination between muscle activation and kinematic sequencing has been associated with reduced performance and increased injury risk, particularly at the shoulder and elbow. However, the integrated relationship between muscle activation patterns and three-dimensional kinematic features during pitching is not well-documented. Purpose: The purpose of this study was to examine the relationship between throwing-arm muscle activation patterns and three-dimensional kinematic characteristics during fastball pitching, with particular emphasis on segmental accelerations, proximal–distal sequencing, and the directional structure of movement quantified using Relative Dimensional Contribution percentage (RDC%). Methods: Ten collegiate baseball pitchers performed fastball pitches while synchronized three-dimensional motion capture and surface electromyography (sEMG) data were collected. Linear and angular kinematics of the shoulder, elbow, and hand were analyzed alongside muscle activation patterns of key upper-extremity muscles. Correlation analyses were conducted to assess relationships between muscle activation and segment accelerations across pitching phases. Results: Pitching demonstrated a clear proximal–distal progression, with linear and angular velocities and accelerations increasing from the shoulder to the hand. Muscle activation patterns reflected this sequencing, with earlier activation of proximal muscles, such as the pectoralis major and anterior deltoid, and later, sharper activation peaks in distal muscles, particularly the wrist extensors. Five muscles (pectoralis major, biceps brachii, anterior deltoid, wrist flexors and wrist extensors showed significant positive correlations with segment accelerations. RDC% analyses revealed that distal segments exhibited increasingly multidirectional motion, with greater medial–lateral and vertical contributions to resultant acceleration at the elbow and hand. Conclusions: These findings demonstrate coordinated relationships between neuromuscular activation and three-dimensional kinematic features during baseball pitching. The integration of sEMG, segmental kinematics, and RDC% provides a comprehensive perspective on proximal–distal sequencing and directional motion control. This approach offers valuable insight into the biomechanical mechanisms underlying pitching performance and may inform future strategies for performance optimization and injury prevention.

Library of Congress Subject Headings

Pitchers (Baseball)--Health and hygiene; Kinematics; Muscles--Physiology

Publication Date

12-18-2025

Document Type

Thesis

Student Type

Graduate

Degree Name

Health and Well-being Management (MS)

Department, Program, or Center

Wegmans School of Health and Nutrition

College

College of Health Sciences and Technology

Advisor

Yong “Tai” Wang

Advisor/Committee Member

Jason Rich

Advisor/Committee Member

Bill Brewer

Campus

RIT – Main Campus

Plan Codes

HLTH-MS

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