Diaphragmatic Facilitation and Upper Extremity Performance in Volleyball Players

Primary outcomes

1. Forced Vital Capacity

   Time frame: 4 weeks

   Forced vital capacity is the maximum volume of air that a participant can forcibly exhale after taking the deepest possible breath. It will be measured by spirometry and recorded in liters. Higher values generally indicate greater ventilatory capacity, whereas lower values may indicate reduced pulmonary capacity or expiratory limitation.

2. Forced Expiratory Volume in One Second

   Time frame: 4 weeks

   Forced expiratory volume in one second is the volume of air that a participant can forcibly exhale during the first second of a forced expiratory maneuver. It will be measured by spirometry and recorded in liters. Higher values generally indicate better expiratory airflow, whereas lower values may indicate reduced expiratory airflow.

3. Ratio of Forced Expiratory Volume in One Second to Forced Vital Capacity

   Time frame: 4 weeks

   The ratio of forced expiratory volume in one second to forced vital capacity represents the proportion of the forced vital capacity exhaled during the first second of a forced expiratory maneuver. It will be calculated from spirometric measurements and reported as a percentage. Higher values generally indicate a greater proportion of air expelled during the first second, whereas lower values may indicate expiratory airflow limitation. The results will be interpreted with consideration of age- and sex-appropriate reference values.

4. Maximal Inspiratory Pressure

   Time frame: 4 weeks

   Maximal inspiratory pressure will be used to assess inspiratory muscle strength, primarily reflecting the function of the diaphragm and other inspiratory muscles. The measurement will be repeated three times, and the highest valid value will be recorded in centimeters of water. A higher absolute pressure value indicates greater inspiratory muscle strength, whereas a lower absolute pressure value indicates weaker inspiratory muscle strength.

5. Maximal Expiratory Pressure

   Time frame: 4 weeks

   Maximal expiratory pressure will be used to assess expiratory muscle strength, particularly the strength of the abdominal and other expiratory muscles. The measurement will be repeated three times, and the highest valid value will be recorded in centimeters of water. A higher pressure value indicates greater expiratory muscle strength, whereas a lower pressure value indicates weaker expiratory muscle strength.

6. Medicine Ball Throw Distance

   Time frame: 4 weeks

   Upper extremity explosive power will be assessed using the Medicine Ball Throw Test. The participant will sit with the back supported against a wall and the legs extended and will be instructed to throw the medicine ball as far as possible. Throwing distance will be measured in meters. A longer distance indicates greater upper extremity explosive power, whereas a shorter distance indicates lower explosive power.

7. Closed Kinetic Chain Upper Extremity Stability Test Score

   Time frame: 4 weeks

   Upper extremity stability, strength, power, and endurance will be assessed using the Closed Kinetic Chain Upper Extremity Stability Test. The participant will assume a push-up position with the hands placed on two markers positioned 90 centimeters apart. The participant will alternately move each hand across the body to touch the opposite marker during the specified test period. The total number of valid touches will be recorded. A higher number of touches indicates better upper extremity functional performance and stability, whereas a lower number indicates poorer performance.

8. Scapular Muscular Endurance Time

   Time frame: 4 weeks

   The functional endurance of the scapular stabilizing muscles will be assessed using the Scapular Muscular Endurance Test. An appropriately sized wooden rod will be positioned between the participant's elbows while both scapulae are maintained in a neutral position. The length of time for which the participant can maintain the standardized test position will be recorded in seconds. A longer duration indicates greater scapular muscular endurance, whereas a shorter duration indicates lower scapular muscular endurance.