Eye-Hand Cross-Dominance and Upper Extremity Performance in Volleyball Players

Eye dominance will be determined using the Miles Test. The participant will focus on a distant target with both eyes open and will then close each eye separately. The eye with which the target remains centered will be classified as the dominant eye. Eye dominance will be used with hand dominance to classify participants as having crossed or non-crossed eye-hand dominance.

Bilateral shoulder flexion, extension, and abduction muscle strength will be measured using a validated handheld myometer. Measurements will be recorded separately for the right and left sides. Higher force values indicate greater shoulder muscle strength, whereas lower values indicate lower muscle strength.

Bilateral elbow flexion and extension muscle strength will be measured using a validated handheld myometer. Measurements will be recorded separately for the right and left sides. Higher force values indicate greater elbow muscle strength, whereas lower values indicate lower muscle strength.

Handgrip strength will be measured bilaterally using a digital hand dynamometer. Three measurements will be performed for each hand, and the mean value will be recorded. Higher values indicate greater handgrip strength, whereas lower values indicate lower handgrip strength.

Hand-eye coordination will be assessed using the Alternate-Hand Wall Toss Test. The participant will throw a ball against a wall with one hand, catch it with the opposite hand, and repeat the sequence by alternating hands. The total number of successful throws and catches completed within 30 seconds will be recorded. A higher number indicates better hand-eye coordination and motor performance, whereas a lower number indicates poorer performance.

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 throw the medicine ball as far as possible. The longest valid throwing distance will be recorded in meters. A longer distance indicates greater upper extremity explosive power.

Upper extremity functional 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 total number of valid alternating touches performed within the specified test period will be recorded. A higher number of touches indicates better upper extremity functional performance and stability.

Scapular stabilizer muscle endurance will be assessed using the Scapular Muscular Endurance Test. An appropriately sized wooden rod will be positioned between the participant's elbows while the scapulae are maintained in a neutral position. The duration for which the participant can maintain the standardized position will be recorded in seconds. A longer duration indicates greater scapular muscular endurance.

Upper extremity and trunk balance, mobility, and stability will be assessed using the Upper Quarter Y-Balance Test. Testing will begin with the non-dominant hand as the reaching hand. Maximum reach distances in the medial, inferolateral, and superolateral directions will be recorded. Greater reach distances and higher composite scores indicate better upper extremity dynamic balance and functional stability.

Reaction time and neuromuscular control will be assessed using the BlazePod light-based reaction system. Participants will respond to randomly activated visual stimuli according to a standardized testing protocol. Reaction time will be recorded in milliseconds. A shorter reaction time indicates faster visual-motor responses, whereas a longer reaction time indicates slower responses.