Inspiratory Muscle Strength and Diaphragm Thickness in People With Shoulder Pain in Tennis Players

This observational case-control study will compare inspiratory muscle function and diaphragm morphology between individuals with shoulder pain and asymptomatic controls. Participants will be allocated into two groups according to the presence or absence of shoulder pain. Inspiratory muscle strength will be assessed by measuring maximal inspiratory pressure (MIP) using standardized procedures. Diaphragm thickness will be evaluated bilaterally using ultrasound imaging at the end of inspiration (Tins) and at the end of expiration (Texp). Pain intensity will be assessed using the Visual Analog Scale (VAS). Upper limb disability will be evaluated using the QuickDASH questionnaire, including the activities of daily living module and the optional sports module. All outcomes will be assessed in a single evaluation session. Between-group comparisons will be performed to analyze differences in inspiratory muscle strength, diaphragm thickness, pain intensity, and upper limb disability between participants with and without shoulder pain.