The goal of this cross-sectional study is to investigate the effects of abdominal bracing, a trunk co-activation maneuver that activates core muscles, on upper extremity performance tests in adolescent female volleyball athletes. The main question it aims to answer is:

-Does performing the abdominal bracing maneuver increase the upper extremity performance in adolescent female volleyball athletes?

This study aims to determine the acute effects of abdominal bracing maneuver on the stability and strength of the upper extremity. Trunk co-activation maneuvers, also known as volitional preemptive abdominal contraction or abdominal stabilization maneuvers, are developed to prevent and treat spinal instability by boosting core muscle activity. Since core muscles are essential for providing proximal stabilization and maximal force during various activities, take part in the energy transfer between the upper and lower extremities, and reduce the load on the joints; performing the maneuver may increase the athlete's performance.

Inclusion Criteria:

• Female adolescent athletes between the ages of 12 and 18
• Attending a volleyball-specific training program at least two times a week
• Not having a systemic and/or neurological disorder
• Not having had a surgery related to upper extremity, lower extremity and/or spine
• Not having had an upper extremity injury for the past six months

Exclusion Criteria:

• Not attending a volleyball-specific training program or attending only once a week
• Having a systemic and/or neurological disorder
• Having had a surgery related to upper extremity, lower extremity and/or spine
• Having had an upper extremity injury for the past six months

All participants were female adolescent volleyball athletes between 12 and 18 years.