The purpose of this graduate student research study is to transform the existing concepts surrounding shoulder strength in baseball players, particularly in the context of retroverted shoulders.

The study aims to investigate the influence of biological age on shoulder strength in comparison to chronological age, providing insights into how these factors might interact in the context of athletic performance. Additionally, the investigators seek to develop a novel framework for injury prevention in baseball, addressing the critical research gap identified in the scope review. Furthermore, the investigators will conduct a comparative analysis between two different countries to deepen the understanding of baseball-related injuries, ultimately fostering a more comprehensive approach to athlete safety and health in the sport.

Inclusion Criteria:

• Able to participate in baseball activities
• All races and ethnicities.
• Speaks and understands English or Japanese.

Exclusion Criteria:

A diagnosis of a current injury that prevents participation in baseball activities.

• Orthopedic conditions (e.g., muscle strain, ligament sprain)
• Vascular history (e.g., blood clots, vascular surgery, varicose veins)
• Neurological history (e.g., stroke, nerve injury, or cognitive impairment)
• Cardiopulmonary conditions (e.g., hypertension, heart disease)
• Any history of bleeding or clotting disorders
• Diabetes, cancer, rhabdomyolysis, or compartment syndrome
• Additionally, not maintaining participant's regular diet on the day of the research will also impact eligibility.

Baseball players from schools in the United States and Japan.