The investigation of the effect of shoulder joint range of motion on the serving accuracy rate of volleyball youth athletes

The Investigation of the Effect of Shoulder Joint Range of Motion on the Serving Accuracy Rate of Volleyball Youth Athletes Aim: This study's primary aim is to examine the effect of shoulder flexibility on service accuracy among youth volleyball players. Another study objective is to evaluate the effectiveness of shoulder stretching exercises in improving shoulder flexibility. Methods: The research population consists of athletes affiliated with volleyball sports clubs operating at the youth level in Sakarya province. The sample consisted of 32 youth athletes, 16 boys and 16 girls. The data were analyzed with SPSS 28 software, and descriptive statistics were presented as arithmetic mean ± standard deviation (X̄ ± SD). The baseline values of the groups were compared with the Independent Sample T-Test; group (2) x time (2) interactions were analyzed with two-way repeated measures analysis of variance. The assumption of sphericity was tested with the Mauchly test; Greenhouse-Geisser or Huynh-Feldt corrections were applied in case of violation. Partial eta squared (ηp²) and Cohen's d were used for effect size assessments. Results: According to the two-way ANOVA results, the time effect was statistically significant (p <0.05) in all movement parameters (flexion, extension, abduction, adduction, hyper-adduction, internal/external rotation, and serve). When evaluated regarding group effect, a significant difference was found only in the external rotation parameter, while no significant difference was observed between the groups in the other parameters (p> 0.05). Group × time interaction was significant in hyper-adduction and served through performance; no significant interaction was found in other movements (p> 0.05). Conclusion: The research results show that regular flexibility exercises statistically significantly increase the serve accuracy of volleyball players. The findings suggest that a progressive improvement in serving performance can be achieved if these exercise programs are applied continuously.