Diaphragmatic Facilitation and Upper Extremity Performance in Volleyball Players

Inclusion Criteria: * Aged between 18 and 30 years. * Regularly participating in volleyball for at least one year. * Training at least twice per week or actively participating in volleyball at the league or tournament level. * No history of a serious upper extremity or trunk injury within the previous six months, i-including injuries affecting the shoulder, scapular region, or spine. * No diagnosed chronic respiratory disease, including asthma, chronic obstructive pulmonary disease, or allergic bronchitis. * Willing and able to provide written informed consent. Exclusion Criteria: * History of surgery involving the upper extremity, spine, or trunk within the previous six months, including shoulder arthroscopy or spinal disc surgery. * Presence of an active musculoskeletal injury, including tendinopathy, bursitis, or ligament injury. * Presence of a diagnosed respiratory disease, including asthma, chronic obstructive pulmonary disease, or bronchiectasis. * Presence of a diagnosed postural or spinal deformity that may affect study assessments, including scoliosis, clinically significant kyphosis, or clinically significant lordosis. * History of a neurological or cardiovascular disease.