Abstract
This study was to examine the effect of a mental training program, including a combination of autogenic training and imagery, on a number of mental skills and on the development of personality traits - psychological hardiness as well as conscientiousness, openness to experience, and neuroticism - in Adolescent male volleyball players. 60 adolescent male volleyball players (aged 15-17) participated in a two-group, pretest-posttest design. The experimental group (n = 30) completed 8-week mental skills training program, including imagery, self-talk, attention control, and relaxation, while the control group (n = 30) followed regular training. Psychological hardiness and selected personality traits were measured pre- and post-intervention using validated scales, and data were analyzed with mixed-design ANOVA and effect sizes. result show significant improvements in psychological hardiness (commitment, control) and personality traits (conscientiousness, openness to experience) in the experimental group (p < 0.01), with modest decreases in neuroticism. Large effect sizes (Cohen's d = 0.57-1.19; partial η(2) = 0.07-0.37) highlight the practical impact of the intervention compared to the control group, which showed minimal changes. Structured mental skills training significantly enhanced psychological hardiness, conscientiousness, and openness, modestly reduced neuroticism, and demonstrated practical impact, supporting its integration into adolescent male volleyball players' holistic development programs.