Volleyball is an interval sport involving consecutive aerobic and anaerobic loads. Strength training based on explosive movements can improve performance in the upper extremities. Strength performance has an important place in this sport. Trunk stabilization is defined as 'proximal stability for distal mobility'. Disorder in any segment of the kinetic chain model will affect the quality of movement in the lower and upper segments.The aim of this study is to examine the relationship between the morphological features of the transversus abdominis, lumbal multifidus (L4-5), internal external oblique muscles, and the anaerobic power of the upper extremity and shoulder girdle functionThis study was designed as a cross-sectional. They will consist of 30 volleyball players between 14-30 years of age. Muscle morphological features of the participants by ultrasound; explosive strength will be evaluated by Medicine Ball Throw test, functional evaluation will be evaluated by Closed Kinetic Chain Upper Extremity Endurance test.

Inclusion Criteria:

• Training for an hour at least 3 days a week for at least 1 year
• Body Mass Index (BMI) below 30 kg/m2
• No concomitant neurological, rheumatological or systemic disease
• Volunteer to participate in the study.

Exclusion Criteria:

• Having any surgery / serious pathology of the spinal column
• Having had an upper extremity injury in the last 6 months that would affect his ability to play volleyball
• Having an injury that requires at least 2 weeks of discontinuation
• Severe musculoskeletal/systemic discomfort during the measurements.

Hacettepe University will be directed from the referred athletes