The sport of volleyball creates considerable dynamic core stability demands. Back injury occurs all too frequently in volleyball. The purpose of this clinical trial is to review functional anatomy, muscle coactivation strategies, assessment of characteristics of effective exercises for the core and effects to upper extremity performance.

Methods: 26 elit female volleyball players (13 experimental, 13 control) will participate. Players will trained as two groups at the same times for 8 weeks. The progressive 3-phase include volleyball-specific training program is presented to improve dynamic trunk stability with exercise ball, elastic bands and on soft grounds. Control group is just trained with phase 2 and 3 exercises.

Phase1: kinesthetic awareness and endurance, with the clinician providing cues to teach achievement of biomechanically neutral spine alignment (with no equipment) .

Phase2:dynamic exercises include progressively higher velocity endurance, coordination, and strength-power challenges integrating upper extremity movements using a stability ball or resistance ball Phase3: volleyball-specific skill while maintaining neutral spine alignment and proprioceptive training using a stability ball, volleyball ball and elastic bands.

Assessments are done previous to join the training programme and on the 8. weeks after completing their programmes. For analysis of the spine; lateral ridge,double leg lowering (core stability test) static trunk flexion and back extension, modified push-ups and sit-ups tests, for upper extremity functions; isokinetics dynomemetre (isomed 2000), closed kinetic chain stability test and soft ball distance throwing tests, for upper extremity proprioception; LP-ART test are used.